musculoskeletal disorders and psychosocial factors at work ... · musculoskeletal disorders and...

Department of Public Health

University of Helsinki

Musculoskeletal disorders and psychosocial factors at work

Effects of a participatory ergonomics intervention in a

cluster randomized controlled trial

Eija Haukka

ACADEMIC DISSERTATION

To be presented by permission of the Faculty of Medicine of the University of Helsinki,

for public examination in the Auditorium of the Finnish Institute of Occupational Health,

Haartmaninkatu 1 A (3rd floor), Helsinki, on Friday 5th November 2010, at 12 noon

Publications of Public Health M206:2010

ISSN 0355-7979

ISBN 978-952-10-4867-8 (paperback)

ISBN 978-952-10-4868-5 (pdf)

http://ethesis.helsinki.fi

Helsinki University Print

Helsinki 2010

Author's address: Finnish Institute of Occupational Health

Topeliuksenkatu 41 a A

FI-00250 Helsinki, Finland

E-mail:[email protected]

Supervisors: Docent Päivi Leino-Arjas

Finnish Institute of Occupational Health

Helsinki, Finland

Professor (emerita) Hilkka Riihimäki

Finnish Institute of Occupational Health

Helsinki, Finland

Reviewers: Professor Clas-Håkan Nygård

University of Tampere

Tampere, Finland

Docent Simo Taimela

University of Helsinki

Helsinki, Finland

Opponent: Professor Allard van der Beek

EMGO Institute, VU University Medical Centre

Amsterdam, The Netherlands

CONTENTS

ABSTRACT .........................................................................................................................................7

LIST OF ORIGINAL PUBLICATIONS ...........................................................................................10

ABBREVIATIONS............................................................................................................................11

1. INTRODUCTION..........................................................................................................................12

2. REVIEW OF THE LITERATURE ................................................................................................14

2.1. Burden of musculoskeletal disorders...........................................................................................14

2.2. Risk factors for musculoskeletal disorders..................................................................................16

2.2.1. Physical workload...............................................................................................................18

2.2.2. Psychosocial factors at work...............................................................................................21

2.2.3. Health-related lifestyle........................................................................................................22

2.2.4. Individual factors ................................................................................................................24

2.3. Ergonomics intervention studies .................................................................................................28

2.3.1. Study designs ......................................................................................................................28

2.3.2. Methodological issues.........................................................................................................30

2.3.3. Challenges encountered in workplace intervention studies ................................................32

2.3.4. The participatory approach .................................................................................................33

2.4. Evidence of the effectiveness of ergonomics interventions in preventing

musculoskeletal disorders...................................................................................................................35

2.4.1. Overview.............................................................................................................................35

2.4.2. Behavioural and physical interventions ..............................................................................36

2.4.3. Organizational interventions...............................................................................................37

2.4.4. Participatory ergonomics interventions ..............................................................................38

2.5. Kitchen work as a target of an ergonomics intervention.............................................................50

3. THEORETICAL FRAMEWORK OF THE STUDY ....................................................................52

4. AIMS OF THE STUDY.................................................................................................................54

5. MATERIALS AND METHODS ...................................................................................................55

5.1. General description of the study..................................................................................................55

5.2. Study designs and subjects ..........................................................................................................56

5.3. Sample size, randomization and blinding....................................................................................57

5.4. Data collection, worker turnover and loss to follow-up ..............................................................58

5.5. The participatory ergonomics intervention .................................................................................59

5.6. Measures......................................................................................................................................62

5.6.1. Musculoskeletal disorders and multiple-site musculoskeletal pain....................................62

5.6.2. Psychosocial factors at work and mental stress ..................................................................63

5.6.3. Perceived physical workload ..............................................................................................64

5.6.4. Covariates ...........................................................................................................................64

5.7. Statistical analyses.......................................................................................................................66

5.7.1. Effects of the participatory ergonomics intervention on musculoskeletal

disorders and psychosocial factors at work ..................................................................................66

5.7.2. Multiple-site musculoskeletal pain and reciprocal associations with psychosocial

factors at work ..............................................................................................................................67

6. RESULTS.......................................................................................................................................68

6.1. Effects of the participatory ergonomics intervention in the prevention of

musculoskeletal disorders (I)..............................................................................................................68

6.1.1. Baseline characteristics.......................................................................................................68

6.1.2. Changes in ergonomics.......................................................................................................70

6.1.3. Effects on health outcomes .................................................................................................71

6.1.4. Effects on perceived physical workload .............................................................................74

6.2. Effects of the participatory ergonomics intervention on psychosocial factors at work

(II).......................................................................................................................................................74

6.3. Occurrence of multiple-site musculoskeletal pain (III)...............................................................77

6.4. Reciprocal associations of multiple-site musculoskeletal pain with psychosocial

factors at work (IV) ............................................................................................................................79

6.4.1. Time-lagged associations....................................................................................................79

6.4.2. Trajectories of multiple-site musculoskeletal pain and psychosocial factors at

work ..............................................................................................................................................80

6.4.3. Associations of psychosocial factors at baseline with multiple-site

musculoskeletal pain trajectories ..................................................................................................82

6.4.4. Association of multiple-site musculoskeletal pain at baseline with psychosocial

work factor trajectories .................................................................................................................83

6.4.5. Psychosocial work factor trajectories in relation to multiple-site pain trajectories ............84

7. DISCUSSION.................................................................................................................................85

7.1. Main findings and comparison to earlier studies.........................................................................85


disorders and psychosocial factors at work in the CRT................................................................85

7.1.2. The occurrence of multiple-site musculoskeletal pain .......................................................90

7.1.3. Association of multiple-site musculoskeletal pain with psychosocial factors at

work and mental stress over time .................................................................................................92

7.2. Methodological aspects ...............................................................................................................96

7.2.1. Validity of the CRT ............................................................................................................96

7.2.2. Clinical importance and generalization of the CRT findings .............................................99

7.2.3. Methodological aspects in studies of multiple-site musculoskeletal pain ........................101

7.2.4. Self-reported outcome measures.......................................................................................102

7.3. Study findings in relation to the theoretical framework of the study ........................................104

8. CONCLUSIONS ..........................................................................................................................106

9. IMPLICATIONS OF THE RESULTS.........................................................................................106

ACKNOWLEDGEMENTS .............................................................................................................108

REFERENCES.................................................................................................................................110

7

ABSTRACT

The primary aim of this study was to examine the efficacy of a participatory ergonomics

(PE) intervention in preventing musculoskeletal disorders (MSDs). Secondly, the effects

of the intervention on psychosocial factors at work as intermediate outcomes were

examined. Thirdly, the occurrence of multiple-site musculoskeletal pain (MSP), as well as

its associations with psychosocial factors at work and mental stress, was studied.

A cluster randomized controlled trial of 504 workers of 119 municipal kitchens in four

large cities in Finland was conducted during the years 2002-2005. The kitchens were

randomized to an intervention (n = 59) and control (n = 60) group. The intervention lasted

11 to 14 months. In eight 3-5 hour workshops, the workers were guided to identify

strenuous work tasks and to seek solutions for decreasing physical and mental workload,

as assisted by a researcher trained in ergonomics. The main outcome measures were the

occurrence of and trouble caused by musculoskeletal pain in seven anatomical sites (neck,

shoulders, forearms/hands, low back, hips, knees, and ankles/feet), localized

musculoskeletal fatigue after the working day, and sick leaves due to musculoskeletal

complaints. The following psychosocial factors were studied as intermediate outcomes:

mental stress, mental strenuousness of work, hurry, job satisfaction, job control, skill

discretion, co-worker relationships, and supervisor support. Data were collected by

questionnaire at baseline and thereafter every three months during the intervention and the

12-month post-intervention follow-up. A total of 402 changes related to ergonomics were

implemented. In the control group, 80 such changes were spontaneously implemented as a

part of normal activity. The intervention did not reduce perceived physical workload and

no systematic differences in any health outcomes were found between the intervention and

control groups during the intervention or during the 12-month post-intervention follow-up.

The effects on the psychosocial factors at work were adverse. At the end of the

intervention, the workers in the intervention group reported more job dissatisfaction,

greater mental stress and poor co-worker relationships compared to the control group. The

adverse overall effects were mainly due to a joint effect of the intervention and

unconnected organizational reforms taking place in the foodservice in two of the

participating cities. The results suggest that intervention as implemented in the present

8

trial is not useful in reducing perceived physical workload, improving unsatisfactory

psychosocial working conditions or preventing MSDs. If organizational reforms are

expected to occur, the introduction of other concomitant workplace interventions should

be avoided. There is a need for further high quality trials to elucidate the effectiveness of

PE interventions.

The co-occurrence of pain in seven anatomical sites was studied in a cross-sectional study

(n= 495 women) at baseline, before the intervention started. About 73% of the women

were experiencing pain in at least two, 36% in four or more, and 10% in six to seven sites.

Thus, MSP was more common than single-site pain (14%) or no pain at all (13%).The

seven pain symptoms occurred in 83 different combinations, in addition to those with no

pain and with pain in one site only. When the co-occurrence of pain was studied in three

larger anatomical areas (neck and low back, upper limbs, lower limbs), concurrent pain in

all three areas was the most common combination (36%). Concurrent pain in all three

areas increased successively with age from 22% in the youngest group (� 40 years) up to

49% in the oldest group (�51 years).

Associations of psychosocial factors at work and mental stress with MSP were studied in a

two-year longitudinal study (n= 385 women). Questionnaire data which were collected at

three-month intervals in the intervention study were used. Since no effects of the

intervention were found on MSDs, the occurrence of MSP, or perceived physical

workload, the randomized design was relaxed. The 3-month prevalence of MSP (defined

as pain at � 3 of seven sites) varied between 50% and 61% during the two-year follow-up.

In time-lagged generalized estimating equations, psychosocial factors at work predicted

MSP being reported three months later, and vice versa, MSP predicted adverse

psychosocial factors at work. Developmental patterns of MSP and psychosocial factors

were identified by trajectory analysis. Four trajectories of MSP prevalence emerged: Low,

Descending, Ascending, and High. A two trajectory model- Ascending or High vs. Low -

yielded the best fit for the psychosocial factors. Poor co-worker relationships, mental

stress and hurry at baseline predicted belonging to the High MSP trajectory. MSP at

baseline predicted belonging to the trajectories of Ascending low job control and mental

stress. Adverse changes in most psychosocial factors were associated with belonging to

the High and Ascending MSP trajectories. The reciprocality of these relationships implies

9

either the existence of two mutually dependent processes, or some shared common

underlying factor(s).

In the daily work of occupational and healthcare professionals, in epidemiological

research, and in connection with further interventions, the evaluation and prevention of

pain at multiple anatomical sites might be useful in addition to considering single-site

pain. Since MSP and psychosocial factors at work seem to be strongly linked together, the

assessment of both parameters in parallel is recommended.

10

LIST OF ORIGINAL PUBLICATIONS

This dissertation is based on the following original articles referred to in the text by their

Roman numerals:

I Haukka E, Leino-Arjas P, Viikari-Juntura E, Takala E-P, Malmivaara A, Hopsu L,

Mutanen P, Ketola R, Virtanen T, Pehkonen I, Holtari-Leino M, Nykänen J, Stenholm

S, Nykyri E, Riihimäki H. A randomized controlled trial on whether a participatory

ergonomics intervention could prevent musculoskeletal disorders. Occup Environ

Med 2008;65:849-56. Originally published online 16 Apr 2008.

doi:10.1136/oem.2007.034579.

II Haukka E, Pehkonen I, Leino-Arjas P, Viikari-Juntura E, Takala E-P, Malmivaara A,

Hopsu L, Mutanen P, Ketola R, Virtanen T, Holtari-Leino M, Nykänen J, Stenholm S,

Ojajärvi A, Riihimäki H. Effect of a participatory ergonomics intervention on

psychosocial factors at work in a randomized controlled trial. Occup Environ Med

2010;67:170-177. Originally published online 7 September 2009.

doi:10.1136/oem.2008.043786.

III Haukka E, Leino-Arjas P, Solovieva S, Ranta R, Viikari-Juntura E, Riihimäki H. Co-

occurrence of musculoskeletal pain among female kitchen workers. Int Arch Occup

Environ Health 2006;80:141-8.

IV Haukka E, Leino-Arjas P, Ojajärvi A, Takala E-P, Viikari-Juntura E, Riihimäki H.

Mental stress and psychosocial factors at work in relation to multiple-site

musculoskeletal pain: a longitudinal study of kitchen workers. Eur J Pain (accepted,

9 September 2010).

The papers are reprinted with the permission of the original publishers.

11

ABBREVIATIONS

BL Baseline

BMI Body mass index

CI Confidence interval

CRT Cluster randomized controlled trial

CTS Carpal tunnel syndrome

CWP Chronic widespread pain

FIOH Finnish Institute of Occupational Health

I Intervention phase

ICC Intraclass correlation

LBP Low back pain

MSD Musculoskeletal disorder

MSP Multiple-site musculoskeletal pain

OA Osteoarthritis

OR Odds ratio

Org - No organizational reform

Org + Organizational reform

PE Participatory ergonomics

PI Post-intervention follow-up phase

PIA Post-intervention assessment (at the end of the intervention)

PI12 The 12-month post-intervention follow-up

PR Prevalence rate

RCT Randomized controlled trial

RR Relative risk

12

1. INTRODUCTION

Musculoskeletal disorders (MSDs) are an important and costly occupational health

problem with consequences for workers, employers and society. About 40 million workers

are affected by work-related MSDs. Almost a quarter of the European workforce report

that they have experienced muscular pain in their neck, shoulders and upper limbs, and

about one in every three suffers from low back pain (LBP). Within the European Union,

MSDs are the single most common cause of sickness absence from work, early retirement,

and disability payments. It is estimated that the direct annual costs of the MSDs account

for 2% of the European gross domestic product (Bevan et al. 2009).

There is a consensus that the etiology of MSDs is multifactorial. There has been a special

emphasis on the effect of physical workload (awkward working postures, forceful

movements, repetitive work, etc.) on MSDs. However, recently the role of psychosocial

factors at work has become a focus of epidemiologic research. Several psychosocial

factors have been found to associate with the occurrence of MSDs, e.g. low job

satisfaction, high job demands, low job control, and low workplace social support.

However, most of the evidence is based on cross-sectional studies. Cross-sectional studies

are valuable if one wishes to elucidate associations between variables, but they do not

usually provide information about the time sequence of the 'explanatory' and 'outcome'

variables. Thus, the need for conducting more longitudinal studies has been emphasized.

In recent years, several studies have observed that multiple-site musculoskeletal pain

(MSP) is even more frequently reported than any single-site pain. It has been suggested

that the basic expectation should be that one regional pain accompanies another,

irrespective of pain site (Croft et al. 2007; Croft 2009). Recently, Swedish researhers in

their population based (n=2329) five-year follow-up study concluded, that having

concurrent low back and neck-shoulder disorders was associated with a higher risk for

sickness absence [odds ratio, (OR) 1.7)] as well as a risk for long-term sickness absence

(OR 2.5) compared to having only low back or only neck-shoulder disorders (Nyman et al.

2007). The majority of studies to date have concentrated on pain and its risk factors at a

13

specific site, most often in the low back, and the risk factors of MSP are not well known.

The need to study the co-occurrence of pain over time and to provide information on why

pain tends to occur at multiple sites has recently been emphasized.

Preventive ergonomics interventions are widely applied in order to deal with MSDs.

However, evidence on which of the interventions are the most effective is lacking. The

participatory ergonomics (PE) approach is commonly recommended when the goal is to

reduce MSDs, and its potential as an effective means to improve unsatisfactory

psychosocial working environment has been emphasized. However, few high quality

studies have been reported and evidence on the effectiveness of PE is scanty. It has been

stated that a robust knowledge on the effectiveness of interventions must be based on

several comparable high quality studies in which the effect of ergonomics interventions on

the prevention or reduction of the MSDs has been rigorously evaluated (Bongers 2009).

With respect to LBP prevention, The European Guidelines Working Group recently

concluded that there is an urgent need for good quality randomized controlled trials (RCT)

to examine the effectiveness of physical, psychosocial and organizational ergonomics

interventions (Burton et al. 2006).

The studies described in this dissertation are part of a larger research programme entitled

'Effectiveness of an ergonomics intervention - a randomized controlled trial' (ERGO-

study) conducted by the Finnish Institute of Occupational Health (FIOH) during the years

2002-2005 in collaboration with municipal kitchens in four large cities in Finland. This

thesis reports the effects of the PE intervention on MSDs and on psychosocial factors at

work and mental stress as intermediate outcomes of the intervention (studies I-II). In

addition, the occurrence of MSP and associations of MSP with psychosocial factors at

work over time are presented (studies III-IV).

14

2. REVIEW OF THE LITERATURE

2.1. Burden of musculoskeletal disordersMSDs constitute a major public health problem in the industrialized countries. MSDs

cause individual suffering, trouble in daily living, and considerable economic and societal

consequences due to short- and long-term work disability and productivity losses (Norlund

and Waddel 2000; Baldwin 2004; Buckle 2005). Low back pain, neck pain and shoulder

disorders are common among working populations and are the main reasons for work-

related consultations in general practice (Weevers et al. 2005; Taimela et al. 2007).

In general population studies in different countries, the lifetime prevalence of back

disorders has varied between 30% and 84% and that of neck disorders has been about 70%

(Riihimäki 2005a). According to representative samples of the Finnish population, chronic

low back and neck disorders have decreased in both genders during the last two decades of

the 20th century (Kaila-Kangas 2007). Still, the lifetime prevalence of back pain was as

high as 76% among women and 77% among men, and that of neck pain 68% among

women and 54% among men. The respective one-month prevalence figures of back pain

were 33% and 28%, of neck pain 37% and 24%, of shoulder pain 23% and 18%, of hip

pain 12% and 8%, and of knee pain 21% and 18%. A recent survey based on self-reported

data from European workers claimed that about 33% of Finnish workers reported work-

related pain in their neck, arms and shoulders. In the descending order of pain reporting,

the Finnish workers ranked as the eighth of all EU member states (Bevan et al. 2009).

According to Finnish statistics in 2007, MSDs were the most common reason for receiving

sickness absence benefits accounting for a total of 35% of all absence periods. There were

almost 126 000 incident sickness allowance periods due to MSDs in 2007. The resulting

benefit expenditures were about 273 million euros making up 36% of all the benefits.

With respect to disability pensions, 24% were due to MSDs. Both the numbers of sickness

benefit days and disability pensions were more common in women (Finnish Centre for

Pensions 2008; The Social Insurance Institution 2008). The direct and indirect costs due to

musculoskeletal pain in Finnish primary health care were about 1 billion euros and when

15

combined with costs due to permanent work disability, the overall losses were estimated to

amount to 3% of the gross domestic product (Mäntyselkä et al. 2001; Mäntyselkä et al.

2002). In all 27 EU Member States, MSDs are the main cause of absence from work, and

in some countries 40% of the costs of workers' compensation are attributable to MSDs

(Podniece 2008).

Multiple-site musculoskeletal pain

Concomitant pain in several sites seems to be common. About three quarters of people

report more than one site of pain, with a median count of three out of a possible count of

ten (Croft 2009). The definition for MSP is not well established. The American College of

Rheumatology (ACR) has developed a definition for chronic widespread pain (CWP).

This definition requires the presence of pain that has been present for at least three months

in the axial skeleton, above and below the waist, and on the left and right side of body

(Wolfe et al. 1990). However, pain in multiple body sites that does not meet these

classification criteria may also deserve attention. For example, MSP might have a stronger

impact on mental health, quality of life and healthcare utilization than single-site pain,

irrespective of whether or not the pain experienced by individuals satisfies the criteria for

CWP (Davies et al. 1998; Carnes et al. 2007).

Several studies have reported that MSP is even more frequent than single-site pain both in

the general population (Picavet and Schouten 2003; Walker-Bone et al. 2004; Carnes et al.

2007; Kamaleri et al. 2008c) and in occupational groups (Molano et al. 2001; Yeung et al.

2002; Alexopoulos et al. 2004; Ijzelenberg and Burdorf 2004; Solidaki et al. 2010). In the

Dutch population, single-site pain during the past 12-months was reported by 25% of the

sample, while 29% reported pain in 2-3 sites and 21% in four or more sites (Picavet and

Schouten 2003). Among the Norwegian population, the respective proportions of subjects

with pain during the past seven days were 17%, 27% and 27% (Kamaleri et al. 2008c).

Carnes et al. (2007) found that over three quarters of a British sample who reported pain

suffered from pain stemming from multiple sites.

Having pain at one site has been shown to increase the risk of developing pain at other

sites and the risk seems to increase with the number of pain sites at baseline (Croft et al.

2007; Kamaleri et al. 2009). MSP was associated with decreased level of functional ability

16

among employees of the City of Helsinki (Saastamoinen et al. 2006) and a sample of the

Norwegian general population (Kamaleri et al. 2008c). Among a representative sample of

Finnish adults, the odds ratio of poor perceived physical work ability and the respondent's

own prognosis of poor future work ability increased from two for single-site pain up to

eight for pain at four sites (Miranda et al. 2010). MSP has been shown to predict both

short- and long-term sickness absence (Natvig et al. 2002; Morken et al. 2003; Nyman et

al. 2007) and permanent work disability (Kamaleri et al. 2008b). MSP commonly co-

occurs with other syndromes (Aggarwal et al. 2006; Hagen et al. 2006) and is associated

with poor mental vitality (Walker-Bone et al. 2004; Hagen et al. 2006). MSP is a

persistent phenomenon and it predicts the risk of a current problem for becoming chronic

(Papageorgiou et al. 2002; Andersson 2004; Kamaleri et al. 2009).

MSP is common already of school age and in adolescence (Jones et al. 2003; Adamson et

al. 2007; Larsson and Sund 2007; Auvinen et al. 2009; Paananen et al. 2010). Thus, in

schoolchildren the one-month prevalence of MSP has varied between 8% (Adamson et al.

2007) and 15% (Jones et al. 2003), depending on the criteria used for MSP and the age of

the studied group. The average number of pain sites appears to be settled by age 20 and

little variation seems to occur thereafter (Croft 2009; Kamaleri et al. 2009).

Based on this knowledge, MSP seems to be more disabling and more severe compared to

local pain and it is a special challenge for occupational and health care professionals.

Nonetheless, the majority of studies examining the occurrence and prognostic factors of

musculoskeletal pain have focused on a specific anatomical site (Mallen et al. 2007) and

the risk factors of MSP are inadequately understood.

2.2. Risk factors for musculoskeletal disorders

MSDs are the single largest category of work-related illness, representing a third or more

of all registered occupational diseases in the Nordic countries, the United States and

Japan. It has been estimated that about 40% of all upper limb disorders in the total US

employed population were attributable to occupational exposures (Punnett and Wegman

2004). In global terms, 37% of LBP appear to be caused by occupation, and work-related

17

LBP has been estimated to be responsible for 818,000 disability-adjusted life years being

lost annually (Punnett et al. 2005). Accordingly, risk factors related to work have been

extensively studied. The World Health Organization has defined 'Work-related

musculoskeletal diseases' as diseases that can be partly caused by adverse working

conditions, or which may be aggravated, accelerated or exacerbated by work place

exposures, or such that may impair working capacity (WHO 1985).

Epidemiologic evidence has accumulated that both physical and psychosocial factors at

work and individual factors play a role although the mechanisms involved in the

development of MSDs are not yet completely understood. These factors interact, they may

reinforce each other and their effects may be mediated by cultural or societal factors. All

of them vary over time from one situation to the next, complicating attempts to clarify

their relationships with the development of MSDs (National Research Council 2001;

Bongers et al. 2006; Marras et al. 2009). Psychosocial risk factors for work-related MSDs

can be categorised into those that are specific to the workplace (low social support at

work, job satisfaction, low skill discretion, low job control etc.) and those that are

individual psychosocial or psychological characteristics, such as depression, anxiety and

mental stress (Sauter and Swanson 1996; Bernard 1997; National Research Council 2006).

Non-workplace factors, which contribute to work-related MSDs possibly influencing

individual responses to workplace exposures, are considered as individual factors. Among

these, gender, age, education, marital status, weight, height, overweight/obesity, smoking,

exercise or sports, other hobbies, drug use, personality, and various comorbidities

(Bernard 1997; Burdorf and Sorock 1997; National Research Council 2001; Buckle and

Devereux 2002; Cole and Rivilis 2006).

The following section will contain an overview of the risk factors of MSDs these being

mainly based on existing review articles. The electronic databases Pubmed and Scopus

were searched.

18

2.2.1. Physical workload

Low back disorders

The reviews on the relationship of physical workload with low back disorders by

Hoogendoorn et al. (1999) and Hansson and Westerholm (2001) were based on cohort and

case-control studies. The former covered studies from the period 1949-1997 and the latter

with publications from 1971- 2000. A recent review (Bakker et al. 2009) considered

cohort studies only from years 1997-2007. The reviews indicate that the evidence is strong

for manual materials handling, bending and twisting postures at work, and whole body

vibration as being risk factors for LBP. With respect to patient handling, the evidence is

moderate. Furthermore, the evidence is strong on standing, walking, and sitting at work

for not increasing the risk of LBP. The summary of the review of Lis et al. (2007) claimed

that prolonged merely sitting did not increase the risk of LBP, whereas sitting more than

half of a workday in combination with whole body vibration and/or awkward postures did

increase the risk. However, these conclusions were based mostly on cross-sectional

studies. A review by Chen et al. (2009), based on 10 prospective cohort and 5 case-control

studies, confirmed that sedentary life style (at work and leisure time) was not a risk factor

for LBP.

Neck and upper limb disorders

The Bone and Joint Decade Task Force has recently summarized the determinants of neck

pain among the working (Côté et al. 2008) and the general populations (Hogg-Johnson et

al. 2008). Both reviews examined the literature from 1980 to 2006. These reviews are the

first in which a sufficient number of cohort studies were available to allow reliable

conclusions to be drawn. The best evidence synthesis among the working population was

based on 19 cohort studies and 1 RCT. The following risk factors of neck pain were

identified: prolonged sitting, repetitive and precision work, prolonged neck flexion, elbow

and shoulder posture while working at a computer, inadequate mouse and keyboard

position, and use of telephone shoulder rests. Preliminary evidence was found that

awkward work postures, poor physical work environment, and exposure to glare might be

associated with neck pain.

19

Some reviews have concluded that repetitive work and static work with arms abducted or

elevated at more than 60 degrees are associated with shoulder disorders (Bernard 1997;

Hansson and Westerholm 2001; Walker-Bone and Cooper 2005). Potential risk factors

include also heavy workload and vibration (van der Windt et al. 2000). In a survey with a

20-year follow-up among the Finnish general population, work exposure to repetitive

movements at baseline increased the risk of incident shoulder disorder with an OR of 2.3

and exposure to vibration with an OR of 2.5. These adverse effects were seen even among

those older than 75 years at follow-up (Miranda et al. 2008a). Hagberg (2002) reviewed

experimental and epidemiological studies and concluded that the scientific evidence is

weak for vibration per se as a risk factor for MSDs, although job tasks with vibrating tools

are associated with MSDs. In a two-year prospective study among newly employed

workers (Harkness et al. 2003), lifting heavy weights with one or two hands, carrying on

one shoulder, lifting at or above shoulder level and pushing and pulling were predictive

factors of new onset shoulder pain.

Two recent reviews have summarised the literature on risk factors related to the carpal

tunnel syndrome (CTS). The occurrence of CTS was associated with high levels of hand-

arm vibration, prolonged work with a flexed or extended wrist, high requirements of hand

force (> 4 kg), high repetitiveness (cycle time < 10 seconds, or performing the same

movements for > 50% of cycle time), and their combination (van Rijn et al. 2009).

Previously Palmer at al. (2007a) had found evidence that regular and prolonged use of

hand-held vibratory tools doubled the risk of CTS. There was also substantial evidence

found for similar or even higher risks from prolonged repetitive flexion or extension of the

wrist, especially in combination with a forceful grip. Repetitive movements, use of hand

force, non-neutral wrist postures, and their combinations, all seem to be associated with

epicondylitis and hand/wrist tendinitis (Bernard 1997; Hansson and Westerholm 2001).

However, most studies on occupational risks of tenosynovitis and epicondylitis have been

crticized since they have been based on job titles rather than specific physical activities at

work (Palmer et al. 2007b).

20

Lower limb disorders

According to D'Souza et al. (2005), few reports exist on occupational factors and disorders

of the lower limbs other than osteoarthritis (OA), but it appears that standing and heavy

physical workload may be associated with ankle and foot pain and plantar fascitis. A

history of occupational activities involving prolonged standing may be associated with

chronic plantar heel pain (Irving et al. 2006). Heavy physical work demands have

increased the prevalence of knee complaints in repeated surveys among male employees in

the Netherlands (deZwart et al. 1997). However, in a prospective study of forestry

workers, no work-related factors predicted incident knee pain (Miranda et al. 2002).

Moderate to strong evidence exists that high physical workload is a risk factor of hip and

knee OA (Bierma-Zeinstra and Koes 2007). Recently Jensen (2008b; a) made a best

evidence synthesis evaluating the associations between hip and knee OA with more

detailes about physical work demands. With respect to hip OA, moderate to strong

evidence was found for heavy lifting, but the burdens have to be at least 10-20 kg and the

duration of exposure at least 10-20 years to clearly increase the risk of hip OA. For

example, for farmers the risk seems to double after about 10 years of farming. With regard

to knee OA, evidence was moderate for a relationship of kneeling and heavy lifting and

moderate for the combination of kneeling/squatting and heavy lifting. Insufficient or

limited evidence was found for climbing stairs or ladders as causes of either hip or knee

OA. There were limitations in some of the studies, e.g. small sample size, poor description

of exposure, and the use of differing diagnostic criteria.

Multiple-site pain

Knowledge on risk factors for MSP is based on single studies since no systematic reviews

are available. In dentists, a high perceived physical workload was associated with the co-

occurrence of musculoskeletal pain at different sites (Alexopoulos et al. 2004). In a study

of nurses, office workers, and postal clerks (Solidaki et al. 2010) the association was

examined with the number of pain sites and a physical demands score which was based on

heavy lifting, working with hands above the shoulder level, repeated bending of the elbow,

repeated hand-arm movements, and kneeling, squatting or climbing stairs. In the

multivariate analysis, the score had a strong graded relationship with the number of pain

sites. Lifting of loads (>15 lbs) with one hand or with two hands (> 24 lbs), pulling (> 56

21

lbs), prolonged squatting, and prolonged working with hands at or above shoulder level

were associated with the onset of widespread pain in a two-year prospective study among

newly employed workers (Harkness et al. 2004). In a three-year follow-up study among a

sample of adults in Manchester, Great Britain, pushing/pulling heavy weights, repetitive

wrist movements, and kneeling were associated with the onset of CWP (McBeth et al.

2003). Repetitive movements of the arm or wrists predicted [relative risks (RR) 4.1 and

3.4] future episodes of forearm pain that commonly co-occurred with other regional pain

(Macfarlane et al. 2000).

2.2.2. Psychosocial factors at work

Several reviews on associations of psychosocial factors at work with MSDs have been

published during the past decade. Many psychosocial factors at work have been found to

be associated with the occurrence of MSDs, such as rapid work pace, monotonous work,

low job satisfaction, low workplace social support, high job demands, low job control,

work stress, non-work-related stress, and high and low skill discretion (Davis and Heaney

2000; Hoogendoorn et al. 2000; Ariëns et al. 2001; Linton 2001; Bongers et al. 2002;

Bongers et al. 2006). However, the conclusions of the reviews tend to be inconsistent with

most of the evidence being based on cross-sectional studies. The review by Hartvigsen et

al. (2004) only considered prospective studies and concluded that there was moderate

evidence of no association between LBP with perception of work, organizational aspects,

and social support at work; with respect to stress at work, the evidence was insufficient.

Macfarlane et al. (2009) evaluated the evidence on associations between psychosocial

factors at work and MSDs based on published reviews. With regard to back pain, the

conclusions were the most consistent for an association with high job demands, low job

satisfaction and low work support. For neck/shoulder pain, consistency in conclusions was

found both regarding high work demands (four reviews out of six reported an association)

and for low job demands (two out of three reviews found an association). For lower limb

disorders, there appears to be only a single review regarding knee pain. Subsequently, a

review of studies among the working population (Côté et al. 2008) concluded that high job

demands, low social support at work and job insecurity are risk factors for neck pain.

Preliminary evidence was found for poor job satisfaction, stress at work and frequently

22

experiencing technical problems with a computer. van Rijn et al. (2009) found no

association between any psychosocial risk factors and CTS.

Multiple-site pain

In the review of Mallen et al. (2007), low social support was one of the 11 generic

prognostic factors associated with at least two regional pain complaints. In a population

based study, dissatisfaction with support from colleagues or supervisors was observed to

increase the risk (RR 4.7) of future episodes of forearm pain that commonly co-occurred

with other regional pain (Macfarlane et al. 2000). Poor social relationships at work and

poor job control predicted the increase of pain and clinical findings in the neck and upper

limbs, low back, and lower limbs in a 10-year follow-up of industrial workers (Leino and

Hänninen 1995). Adverse work-related psychosocial factors and high levels of individual

psychological distress predicted the onset of musculoskeletal pain at a one-year follow-up

with similar effects across the anatomical sites (Nahit et al. 2003). In a two-year

prospective study among newly employed workers, those who reported low job

satisfaction, low social support and monotonous work had an increased risk of new-onset

widespread pain (Harkness et al. 2004).

Leino and Magni (1993) conducted a 10-year follow-up study among employees in the

engineering industry and found that symptoms related to mental stress predicted an

increase in a sum score of musculoskeletal pain at several sites, and that the pain sum

score predicted an increase in stress symptoms.

2.2.3. Health-related lifestyle

Shiri at al. recently published two meta-analyses on the relationships of overweight,

obesity and smoking with LBP (Shiri et al. 2010a; b). Overweight and obesity increased

the prevalence of LBP. The associations were strongest for seeking care for LBP (pooled

OR 1.6) and chronic LBP (OR 1.4). Obesity also increased the incidence of LBP (OR 1.5).

The findings pointed to stronger associations in women than in men. Both current and

former smokers were observed to have a higher prevalence and incidence of LBP than

never smokers, with the associations being strongest for disabling (OR 2.1) and chronic

(OR 1.9) LBP. Male smokers were at a higher risk of LBP than female smokers. In their

23

previous systematic review, Shiri at al. (2007) concluded that overweight, long smoking

history, high physical activity and a high serum C-reactive protein level were associated

with lumbar radicular pain and sciatica. In her review Kauppila (2009) found that smoking

and high serum cholesterol levels were most consistently associated with disc

degeneration and LBP. Miranda et al. (2008b) studied the one-year incidence of LBP

according to age group in a Finnish industrial population. Health behaviour, defined as a

sum score of overweight, smoking and lack of physical activity, increased the risk of LBP

only among those 50 years or older (RR up to 2.8), whereas physical workload predicted

LBP among those younger than that age.

Two recent systematic reviews published by Hogg-Johnson et al. (2008) and Côté et al.

(2008) evaluated the determinants of neck pain. The former found evidence that exposure

to passive smoking in adolescents increased the risk of neck pain. The latter review

summarized that smoking increased the risk of neck pain among the working population.

A review byViikari-Juntura et al. (2008) reported some associations between body weight

(weight, BMI) and shoulder disorders. Smoking was associated with shoulder disorders

but only in studies examining occupational populations. Obesity is reported to be a risk

factor for CTS (Walker-Bone et al. 2003; Hooper 2006) and hip and knee OA (Hooper

2006; Wearing et al. 2006; Bierma-Zeinstra and Koes 2007). In the systematic review of

Irwing et al. (2006) increased BMI was associated with chronic plantar heel pain in a non-

athletic population. Obesity may also have a profound effect on soft-tissue structures, such

as tendons, fasciae, and the cartilage, in addition to being a risk factor for bone and joints

disorders (Wearing et al. 2006).

There is moderate to strong evidence that high-intensity sporting activities are risk factors

for hip OA (Bierma-Zeinstra and Koes 2007), but leisure time sports or exercise were not

found to be risk factors of LBP (Hoogendoorn et al. 1999; Bakker et al. 2009). A Dutch

research group (Hamberg-van Reenen et al. 2007) carried out the first review of the

relationship between physical capacity and future LBP and neck/shoulder pain based on

longitudinal studies. They found strong evidence that there is no relationship between

trunk muscle endurance and the risk of LBP and inconclusive evidence for a relationship

between trunk muscle strength and mobility of the lumbar spine and the risk of LBP.

Evidence was inconclusive also for the associations between physical capacity measures

24

with the risk of neck/shoulder pain. Instead, Côté et al. (2008) claimed that low to

moderate physical capacity of neck and shoulder musculature was associated with an

increased risk of neck pain.

Multiple-site pain

Current smoking was associated with an increased risk of chronic pain in multiple

locations and with CWP in both genders among the general rural population (Andersson et

al. 1998). Smokers, overweight subjects and those with low physical activity have

reported a greater number of pain sites (Walker-Bone et al. 2004; Kamaleri et al. 2008a).

Jones at al. (2003) stated that high levels of sports activity predicted the onset of

widespread pain among schoolchildren (RR 1.9). Finnish researchers have studied MSP

among adolescents (Paananen et al. 2010). They found that a high physical activity level,

long sitting time, short sleeping time, and smoking were associated with MSP in both boys

and girls though the associations were stronger in girls. In addition, MSP was associated

with overweight in girls.

2.2.4. Individual factors

Women tend to report more MSDs than men. The gender difference seems to be more

distinct for neck and upper limb disorders (Hooftman et al. 2004; Strazdins and Bammer

2004). Strazdins and Bammer (2004) examined why employed women are much more

likely than men to experience upper body disorders. The gender differences were

explained by risk factors at work (repetitive work, poor ergonomic equipment) and at

home (less opportunity to relax and exercise outside of work). Parenthood exacerbated the

gender difference with mothers reporting having the least time to relax or exercise. The

gender segregation of women into sedentary, repetitive and routine work and the

persisting gender imbalance in domestic work were concluded to be interlinking factors

that accounted for the gender differences in MSDs.

A Danish research group has recently published two large population based studies of

twins aged 20-71 years (Hartvigsen et al. 2009; Leboeuf-Yde et al. 2009). A cross-

sectional survey examined 34 902 twins (Leboeuf-Yde et al. 2009) and it showed that

women were more likely to report MSDs and to have had pain for longer periods than

25

men. Neck pain and LBP was common already at the age of 20, with the prevalence

increasing slowly with age until reaching a peak around middle age. Similar patterns were

noted for radiating pain. Pain was reported to be more long lasting in the older groups. In

the analyses of 15 328 twins, genetic susceptibility explained about 38% of lumbar, 32%

of thoracic, and 39% of neck pain (Hartvigsen et al. 2009).

Other twin studies have suggested that both disc degeneration and back pain contain a

genetic component. A variety of definitions of back pain problems have been used in

genetic studies that could influence responses and heritability estimates since these have

varied widely in the scientific literature, explaining from 0% to 57% of the variance in

back pain reporting (Battie et al. 2007). A recent narrative review by Kalichman and

Hunter (2008) reviewed knowledge of heritability of intervertabral disc degeneration. The

review covered the literature from 1950 to 2007. Familial predisposition to disc

degeneration was observed to be high. Heritability estimates ranged from 34% to 61% in

different spine locations. Fejer et al. (2006) examined a large population based group of

twins (n= 33 794) and noted that genes play a significant role in neck pain, particularly in

women. The overall genetic effect of lifetime neck pain was observed to be 44%. There

was a statistically significant difference in heritability between males and females (34%

vs. 52%). However, the genetic effect became gradually less important with increasing

age. In other words, environmental factors dominate almost completely in the older age

groups. Hartvigsen et al. (2005) reported that genetic factors do not play an important role

in the liability to neck pain in individuals 70 years of age or older. Previous

musculoskeletal pain is a risk factor for neck pain and ethnicity is possibly associated with

neck pain (Côté et al. 2008).

Multiple-site pain

MSP generally increases with age (Bingefors and Isacson 2004). Women have been

shown to report a greater number of pain sites than men (Picavet and Schouten 2003;

Walker-Bone et al. 2004; Kamaleri et al. 2008a) and this trend has been seen already in

adolescents. Paananen et al. (2010) reported that 40% of girls and 23% of boys had

experienced MSP during the past six months. Auvinen et al. (2009) found that the

prevalence of MSP during the past six months increased from 15% in girls and 9% in boys

at the age of 16 years up to 27% and 15%, respectively, at the age of 18 years. Kamaleri et

26

al. (2009) observed a relative stable pattern of reporting the number of pain sites across

adulthood. About 46% of the participants reported the same number of pain sites 14 years

later, plus or minus one site. The average number of pain sites appears to be set by the age

of 20. Little variation in the stability was seen by age or birth cohort, except for a small

decline occurring between 60 and 74 years (Croft 2009; Kamaleri et al. 2009).

Genetic factors may be associated with reporting pain at multiple sites (Zubieta et al.

2003). In the Danish twin study (Hartvigsen et al. 2009), patterns of pain occurrence in

three spinal regions (cervical, thoracic, lumbar) were examined. It was found that the

heritability of having pain in all three areas was 35%, i.e. the highest of all combinations.

Mikkelsson et al. (2001) examined the pattern of familial aggregation of widespread pain

in 11-year-old Finnish twins. In girls 56% and in boys 35% of the variation in liability was

accounted for by familial factors.

In summary, there is a considerable body of epidemiologic literature which has examined

associations of physical workload with MSDs, particularly with back disorders. In

addition, associations of psychosocial and individual factors with MSDs have been

studied. However, prospective studies are in the minority and evidence is largely based on

cross-sectional or case-control studies. This is particularly true of neck and upper limb

disorders. There are few studies on lower limb disorders these being mainly concerned

with hip and knee OA. Most of the existing evidence on associations of psychosocial

factors at work with MSDs is based on cross-sectional studies. Although MSP is more

common than single-site pain, the studies have typically examined separately at pain in

different single anatomical sites and thus the risk factors for MSP remain largely

unknown. However, it seems that single-site pain and MSP may share many predictive

factors. A summary of findings on associations of physical and psychosocial risk factors

with the various MSDs based on the literature is shown in Table 1.

Available evidence of risk factors suggests that workplace interventions aiming at

reducing physical workload and improving psychosocial working conditions could have

potential for the prevention of MSDs. In addition, interventions targeted to improve health

behaviour (avoiding overweight/obesity and smoking) may be beneficial. There is varying

evidence about the role of leisure time physical activity, and the role of physical capacity

27

as a protective factor for MSDs is unclear. More and more research addressing genetic

factors in relation to MSDs has been conducted over the past decades, and evidence has

accumulated that there are major genetic influences involved in the development of

MSDs. Nonetheless, little is known about the roles of individual genes or the pathways

and mechanisms through which they influence pain problems (Battié et al. 2007).

Table 1. Associations of work-related physical and psychosocial risk factors with MSDs, asbased on literature. Osteoarthritis (OA), multiple-site pain (MSP)

*Both physical and psychosocial risk factors for MSP were based on single prospective studies.†Based on reviews: low back disorders (cohort and case-control studies), neck disorders (cohortstudies, 1 RCT), upper limb disorders (mostly cross-sectional studies), hip and knee OA (mostlycase-control and cohort studies). ‡ Based on two reviews: one comprised of cohort studies and oneRCT, the other was an overview of the reviews (most studies were cross-sectional).

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28

2.3. Ergonomics intervention studies

In order to control and deal with the burden of MSDs, a variety of preventive ergonomics

interventions have been conducted. Studies with rigorous designs and methods are needed

in order to determine which of these are the most (cost) effective in reducing MSDs.

Causal inference is often challenging in intervention research. If changes are observed, can

these be attributed to the intervention? The ideal type of study in establishing causality in

terms of internal validity is a RCT. The results of RCTs are considered as the 'gold

standard' and the basis of 'evidence-based practice' in intervention research. Quasi-

experimental studies are frequently used, when random assignment is not possible or

feasible (Rothman and Greenland 1998; Grimshaw et al. 2000; Franceshi and Plummer

2005).

2.3.1. Study designs

Randomized controlled trials

In RCTs, individuals, and in cluster randomized trials (CRTs), groups of people or intact

social units (e.g. workplaces, schools, medical practices, cities), are randomly allocated to

an intervention or a control group. In CRTs, outcomes are measured on the individuals

within clusters. CRTs are used to evaluate group interventions and individual interventions

where group level effects are relevant. CRTs are also considered when the intervention is

given to individuals but might affect others within that cluster. In the evaluation of

complex interventions in which several factors may act interdependently at various levels

of an organization and have an effect on many processes and outcomes, cluster designs

may be useful (Donner and Klar 2000; Atienza and King 2002; Medical Research Council

2002).

The aim of randomization is to avoid confounding and selection bias by creating

comparable groups with respect to any known or unknown potential confounding factors.

A control group is needed to differentiate between change and effect. The prospective

design with at least one measurement before and at least one after the intervention makes

it possible to study changes over time. The effect is estimated by comparing what

happened in the intervention group with what happened to those without the intervention.

29

Blinding and use of placebo treatment are other methodological advantages offered by

RCTs. The purpose of blinding is to eliminate bias resulting from the expectations of

participants or researchers with respect to outcomes. In single-blind trials, it is either the

participants or the researchers who are unaware of the results of the randomized

assignment. In double-blind trials, neither the participants nor the researchers or those

administering the interventions and assessing the outcomes (care providers, outcome

assessors) know who belongs to the control and the intervention group. Placebo treatment

is important to distinguish the effect of a specific intervention from the effect of a sham

intervention. Unfortunately, blinding and use of the placebo are commonly impossible in

ergonomics and other workplace interventions (Shannon et al. 1999; Jüni et al. 2001;

Buring 2002; Green 2002; Kristensen 2005).

When compared with an individually randomized trial, the CRT is more complex to

design and it requires more participants to obtain equivalent statistical power. The power

of a CRT depends more on the number of groups randomized rather than on their size. The

number of groups randomized should be large enough in order to yield similar

distributions of baseline characteristics among the groups. Since participants within a

cluster are more likely to have similar outcomes, the outcomes are not completely

independent. This clustering effect and variation within and between clusters must be

taken into account in the statistical analyses (Rothman and Greenland 1998; Campbell et

al. 2000; Donner and Klar 2000; Atienza and King 2002; Green 2002; Medical Research

Council 2002; Campbell et al. 2004). Reporting of CRTs requires additional consideration,

and an extended CONSORT statement including a checklist of items that should be

included in the trial report, has been published (Campbell et al. 2004).

Quasi-experimental designs

In controlled before-after studies (pre-post / post-only non-equivalent control group

design), the groups are assigned to intervention and comparison groups without random

assignment. It is important that there should be minimal differences between the

intervention and control group at baseline regarding the outcome measures, confounding

factors and other variables thought to influence the estimation of the effect of the

intervention. The major problem with such a design is that the groups might not be the

similar before the intervention. Uncontrolled before-after studies (the pre-post/ post-only

30

one-group designs) with no random assignment and no comparison group are the weakest

designs. In these studies, it is difficult or impossible to attribute changes in the outcome to

the intervention (Shannon et al. 1999; Grimshaw et al. 2000).

Study design quality has been observed to be inversely associated with the reported

magnitude of effects; it seems that the more rigorous the study design, the weaker the

effects which can be found (Volinn 1999; Grimshaw et al. 2000; Neumann et al. 2010).

The effects based on uncontrolled before-after studies have been larger than those based

on controlled before-after studies. In randomized studies, the effects have been smaller

than in studies using quasi-experimental designs.

2.3.2. Methodological issues

Internal and external validity in randomized trials

In RCTs, internal validity is threatened by several sources of bias. Selection bias may

occur if there is an error in the allocation of individuals or groups to the intervention and

control groups. The researchers may have conscious or attitudinal preferences with respect

to the allocation, the consequences of which are avoided if the allocation sequence can be

generated by using a computer algorithm. The allocation sequence must be concealed

from the researchers enrolling the participants. Dropouts may lead to increasingly different

groups (attrition bias) if those who drop out are systematically different from those who

remain in the study. Unequal additional interventions distinct from the intervention under

evaluation (performance bias), and an influence by a knowledge of the subjects'

assignment on the assessment of outcome (detection bias) are other threats to internal

validity in randomized designs (Jüni et al. 2001).

There are further potential influences that can diminish the effect of an intervention. The

subjects in the control group may also receive the intervention (contamination), e.g. when

participants move from one group to another during the intervention. Non-compliance

occurs when subjects in the intervention group do not follow the intervention protocol, i.e.

they do not 'take the pill' that they are supposed to take. The 'Hawthorne effect' refers to

the possibility that the behaviour of the subjects in the intervention group may alter simply

31

because they consider that they are under observation (Shannon et al. 1999; Jüni et al.

2001; Buring 2002; Green 2002; Kristensen 2005).

External validity refers to the generalisability of the results. Causal inference based on a

study has external validity if it can be transferred from the study's unique settings to other

situations: other subjects, populations or workplaces. Information pertinent to the

assessment of external validity includes a detailed description of participants (age, gender,

occupation, work experience etc). The manner of recruitment (volunteers vs. all workers)

is relevant, since results obtained from volunteers are often not generalizable to the wider

population. The number of dropouts and the differences between them and non-dropouts

should be reported. Details of the intervention process and content need to be explicitly

described to enable the assessment of external validity. Contextual factors should be

considered as they can have an influence on the effectiveness of an intervention. As an

example, an ergonomics intervention might have a larger impact on a workplace where

ergonomics has not been considered compared to the situation in a workplace where

attention has already been paid to ergonomics (Goldenhar and Schulte 1996; Shannon et

al. 1999; Jüni et al. 2001).

Study quality

In the literature, various proposals for improvement of study quality will be put forward.

Intervention studies should preferably have a theoretical basis that includes a model of the

possible causal processes involved. If there is no knowledge or theory on the links

between the intervention and the desired outcome, it is difficult to understand how an

intervention works (Goldenhar and Schulte 1996; Shannon et al. 1999; Kristensen 2005).

Attention should be paid to the selection of samples, adequate sample size, and duration,

exposure to and intensity of intervention (Goldenhar and Schulte 1996; Buring 2002;

Green 2002; Silverstein and Clark 2004; Kristensen 2005). In order to detect changes in

outcomes, a sufficiently long enough follow-up is needed due to latency periods in the

development of MSDs. No absolute limits can be set, but a follow-up time of one year, or

at least six months, has been proposed (Westgaard and Winkel 1997; Driessen et al. 2010).

Since the latencies are for the most part still unknown, it is recommended that multiple

follow-ups should be attempted if feasible, and both short- and long-term effects should be

32

measured (Karsh 2006). Valid and reliable measurements are needed to ascertain whether

the intervention was carried out as intended, whether the intervention led to the intended

changes in exposure, and whether the changes in exposure led to the anticipated effect on

health outcomes (Kristensen 2005). With all interventions, but especially when using a

multiple- component intervention, measurement and reporting on the effects of the

intervention on intermediate outcomes needs to be emphasized (Karsh et al. 2001).

Measurements of potential confounders or effect modifiers, appropriate and adequate

statistical methods and accounting for losses to follow-up are needed. Analyses should

follow an intention- to- treat principle, i.e. regardless of whether or not the intervention is

completed or received, the subjects or clusters are kept in their original groups. Evidence

of compliance with the intervention, potential contamination between the groups, and co-

interventions also need to be considered (Buring 2002; Green 2002; Silverstein and Clark

2004).

Process evaluation

A careful evaluation of the intervention process is important, based on a systematic

documentation of how the intervention was carried out. This can help in the interpretation

of the study findings and explain how and why changes were or were not achieved. The

evaluation provides feedback for improving the intervention in the future. The results can

be used when the intervention is repeated in another setting and help others to avoid

pitfalls (Goldenhar et al. 2001). It is important to detect if the intervention, even one

deemed effective, was not fully implemented such that not all particpants were exposed to

it (programme failure) or whether it worked poorly although all participants were involved

(theory failure) (Kristensen 2005).

2.3.3. Challenges encountered in workplace intervention studies

Executing controlled intervention studies in workplaces is difficult. It is also time-

consuming and costly (Schulte et al. 1996; Volinn 1999; Karsh et al. 2001). Worksites

with a large number of workers doing the same tasks largely belong to the past and studies

are confronted with unplanned changes beyond the researchers' control. Workforce or

manager turnover must be taken into account. Rapid business or market plan changes, and

changes in production processes that influence work assignments and exposure levels may

33

occur and these are largely unforeseen when the intervention is being planned (Cole et al.

2003; Silverstein and Clark 2004; Heaney and Fujishiro 2006).

It is essential that workplaces approve of the intervention study and perceive that they will

gain benefits from participating in it. Both management and workers should comply with

the concept of random assignment between an intervention and a control group. This is not

always the case. Workplaces participating in an intervention and believing that it will be

effective might have difficulties to accept the use of a control group. If the intervention

being tested is believed to be effective, it might be difficult for the workplaces to justify

having a control group due to financial aspects (Braunholtz et al. 2001; Karsh et al. 2001;

Kristensen 2005). Those outside the trial should not receive inferior care simply because

of not being in the trial. Thus, close collaboration, adequate communication, and mutual

commitment between researchers, workers and management are all necessities. The

successful conduct of an intervention requires interdisciplinary teams, in which

understanding and respect between disciplines can promote the ability to meaningfully

work together (Schulte et al. 1996; Kristensen 2005).

2.3.4. The participatory approach

The participatory method is commonly used in the design and analysis of work systems

(Brown 2005) and its advantages have been discussed especially in relation to PE (Kogi

2006). Along with an increased utilization of participatory methods, it has been recognised

that ergonomics experts alone cannot achieve successful and widespread implementation

of ergonomics in the workplace (Haines and Wilson 1998; Kogi 2006). PE is a complex

and ambiguous concept. No general agreement about the term exists (Haines and Wilson

1998). Wilson and Haines (1997) have proposed that PE refers to 'the involvement of

people in planning and controlling a significant amount of their own work activities, with

sufficient knowledge and power to influence both processes and outcomes in order to

achieve desirable goals'. Imada (1991) defines PE as 'a macroergonomic approach to the

implementation of technology in organizations that requires end users to be highly

involved in developing and implementing the technology' and Nagamashi (1995) as 'the

workers active involvement in implementing ergonomic knowledge and procedures in

their workplace supported by their supervisors and managers, in order to improve

34

working conditions and product quality' whereas Kuorinka (1997) considers PE as

'practical ergonomics with participation of the necessary actors in problem solving'.

A characteristic of most PE interventions is the formation of some type of team or

committee consisting of workers or their representatives, managers, health and safety

personnel, ergonomists, and sometimes research experts. This team usually receives

training in ergonomics from an expert to become familiar with ergonomic principles,

workplace specific risk factors and how this knowledge can instigate improvements

(Theberge et al. 2006; IWH 2008; van Eerd et al. 2008). The expert may also give

training in interpersonal, communication and team-building skills. The expert may

function as a resource person, i.e. an individual familiar with the available skills and

knowledge to help in problem-solving and who can contribute to the design of the

intervention. The role of the expert is varied and complex but in all participatory

approaches he/she acts as an agent or facilitator of change (Brown 2005).

Furthermore, a successful PE program requires that the responsibilities of team members

in problem-solving, and developing and implementing changes, are well defined, that the

group makes decisions through group consultation and that the management is involved in

any decision requiring resources and implementation. Support, time and financial

resources from the top levels of management are key factors in the success (IWH 2008;

van Eerd et al. 2008).

The PE approach has several advantages. When the workers are involved in the process as

the best experts of their own work, a feeling of solution ownership is generated, leading to

increased job satisfaction and commitment to the changes being implemented.

Participation represents a learning experience for the individuals involved, as well as

giving them more self confidence, competence and independence. It has been suggested

that worker participation can play a role in reducing stress at work.

There can be disadvantages encountered in PE, e.g. the workers' unwillingness to

participate, or the organizational structure may limit the degree of worker participation.

True commitment from the top management may be difficult to obtain. The process may

encourage workers to develop unrealistic expectations or it may provoke envy and

35

dissatisfaction among those not involved in the improvement process (Haines and Wilson

1998; Brown 2005).

2.4. Evidence of the effectiveness of ergonomics interventions inpreventing musculoskeletal disorders

2.4.1. Overview

When the current intervention study was planned, the scientific literature was scrutinized,

coming the conclusion that no high-quality studies had been reported on the effectiveness

of ergonomics interventions and that sound evidence was lacking (van Poppel et al. 1997;

Westgaard and Winkel 1997; Volinn 1999; Lincoln et al. 2000; Linton and van Tulder

2001). In recent years, a few RCTs have been reported and the number of systematic

reviews in this area has increased. Most of the studies have focused on behavioural (e.g.

physical training of the worker, advice or education about working methods and

techniques or the use of personal protective equipment) and physical interventions (e.g.

redesign of physical work environment, working aids or tools, lifting and transfer aids for

manual materials handling), whereas organizational intervention studies are still sparse.

Organizational interventions occur at company, job or task level and focus on work

processes, practices, and policies of workplaces (i.e. job rotation, job enlargement,

modification of the production system). Such interventions often have an impact on both

physical and psychosocial load of the workers (Goldenhar and Schulte 1996; Westgaard

and Winkel 1997; Zwerling et al. 1997). The PE approach is recommended to reduce

MSDs (Cole et al. 2005; Hignett et al. 2005; van der Molen et al. 2005a; Rivilis et al.

2006; Rivilis et al. 2008) and its potential as an effective means to improve unsatisfactory

psychosocial work factors has been emphasized (Haims and Carayon 1998; Heaney and

Fujishiro 2006; St-Vincent et al. 2006). It has also been claimed to be the most efficient

way to improve ergonomics in the workplace (Hagberg et al. 1995). However, evidence on

its effectiveness continues to be scanty. In multi-component interventions, different

intervention types are combined (Feuerstein et al. 2000; Karsh et al. 2001; Gatty et al.

2003). They might have a greater chance of success than single interventions in preventing

MSDs (Karsh et al. 2001; Gatty et al. 2003; Silverstein and Clark 2004; Tveito et al. 2004;

36

Cole et al. 2006), but it is not possible to recommend which components should be

included and how they should be balanced (Burton et al. 2006).

Despite the increasing number of studies, they seem mostly to suffer from low

methodological quality. All the reviews have concluded that good quality RCTs are

urgently needed to provide convincing evidence on the effectiveness of the interventions.

Burton et al. (2006) highlighted the need for conducting especially CRTs targeted to study

the effectiveness of physical, psychosocial and organizational ergonomics interventions.

This literature review is mainly based on recent systematic reviews. In addition, some

original randomized or non-randomized studies will be described. Interventions using the

PE approach are reviewed separately. Tertiary prevention interventions were excluded

because they are beyond the scope of this thesis. The reviews were favoured in which the

authors had used some of the several guidelines developed for the reporting and a quality

assessment of studies, e.g. the Delphi list (Verhagen et al. 1998), the GATE checklist

(EPIQ 2004), or the criteria recommended by the Cochrane back review group (van Tulder

et al. 2003).

2.4.2. Behavioural and physical interventions

Low back pain

Back schools are not recommended for the prevention of LBP (Linton and van Tulder

2001, Burton et al. 2006, Bigos et al. 2009). The use of back belts, lumbar supports

(Jellema et al. 2001; Linton and van Tulder 2001; van Poppel et al. 2004; Ammendolia et

al. 2005; Bigos et al. 2009), and shoe inserts or orthoses have also been shown to be

ineffective (Burton et al. 2006, Bigos et al. 2009). Training in manual materials handling

or the use of lifting equipments is not effective if it is used as the only intervention (Bos et

al. 2006; Martimo et al. 2008; Bigos et al. 2009). Training and education combined with

the use of mechanical or other aids may be effective, which can be partly explained by a

decrease in the frequency of manual lifting (Bos et al. 2006).

When technical lifting devices were part of a more comprehensive intervention, a

reduction in physical work demands and low back disorders was found, particularly when

the PE approach was used (van der Molen et al. 2005a). A recent systematic review by

37

Driessen et al. (2010) included only RCTs and surveyed studies from the time period 1988

to 2008. These investigators concluded that physical ergonomics interventions were not

effective in the prevention of LBP. Thus, there seems to be insufficient evidence to

recommended physical (or organizational) ergonomics interventions alone for the

prevention of LBP (Linton and van Tulder 2001; Burton et al. 2006).

Pain in the neck and upper limbs

Intervention studies concerning neck and upper limb disorders are considerably less

common than those on LBP. The systematic review of Brewer et al. (2006) examined

articles published from 1980 to 2005. They found moderate evidence for a positive effect

of alternative pointing devices and no effect of workstation adjustment, rest breaks, and

exercise during the breaks among computer users. The systematic review by Driessen et

al. (2010) showed that physical ergonomics interventions were not more effective on short

and long term neck pain prevalence or incidence, but possibly could reduce the intensity

of neck pain in the long run. However, the number of studies was limited and targeted

mostly office workers, and populations, interventions and outcomes were heterogeneous.

Boocock et al. (2007) reported moderate evidence that mouse and keyboard design led to

positive effects in neck and upper limb conditions among video display unit (VDU)

workers, but among manufacturing workers, the evidence was insufficient. Norwegian

researchers have published protocols of Cochrane systematic reviews on workplace

interventions for neck pain (and LBP), and it can be predicted that the results of these

reviews will add to knowledge in this area in the near future (Aas et al. 2009a; Aas et al.

2009b).

Lower limb pain

No literature on the effectiveness of work-related interventions regarding lower limb pain

was found.

2.4.3. Organizational interventions

A narrative review by Westgaard and Winkel (1997) and a systematic review conducted

ten years later by Boocock et al. (2007) showed consistently that there was insufficient

evidence for demonstrating any benefits of organizational interventions. In the latter

review, only two relevant studies were identified. These involved no randomization, were

38

of low quality, and showed no improvements in outcome measures. Driessen et al. (2010)

stated that RCTs on organizational ergonomics interventions to prevent and reduce neck

pain and LBP were lacking. Many other authors have recently concluded that evidence on

the effectiveness of organizational interventions is scanty (Murphy and Sauter 2004;

Bongers et al. 2006; Burton et al. 2006; Heaney and Fujishiro 2006; St-Vincent et al.

2006; Podniece 2008). Few studies exist on the effectiveness of work-rest schedules,

breaks, task rotation and task enrichment, but the results are contradictory and no

conclusive evidence is available (Bongers et al. 2006; Podnieze 2008). Two reviews have

reported on the effects of workplace reorganization on psychosocial factors and health,

with reference to the 'demand-control-support' model (Bambra et al. 2007; Egan et al.

2007). Limited and inconsistent evidence was found to support health benefits when

employee control improved, demands decreased or support increased. Two studies of

participatory interventions occurring alongside redundancies reported worsening of

employee health (Egan et al. 2007). Task-restructuring interventions that increased

demand and decreased control had an adverse effect on health, and an increase in

workplace support did not appear to mediate this relationship (Bambra et al. 2007). van

der Klink et al. (2001) reported a small and non-significant effect size for the few

organizational interventions that were focused on work-related stress.

One CRT (Tsutsumi et al. 2009) and one non-randomized controlled before-after study

(Kobayashi et al. 2008) have been published after the above mentioned reviews. They

showed positive effects on improving mental health and job performance by using the

participatory approach. These studies are reviewed below.

2.4.4. Participatory ergonomics interventions

Only one systematic review on the effectiveness of the PE interventions was found. Rivilis

et al. (2008) used a best evidence synthesis where 12 studies were evaluated to be of

sufficient methodological quality to be included. Nine 'medium' and three 'higher' quality

studies showed partial to moderate evidence that the PE interventions had had a

favourable impact on musculoskeletal symptoms and reduced workers' compensation

claims and sickness absence. However, random allocation or adjustments for differences

between groups at baseline were used only in three studies. Other methodological flaws

39

were insufficient documentation of participation in the PE process and poor reporting of

consideration of potential confounders. In the studies graded as 'low' quality, also deficient

reporting of co-interventions and of risk factor measurement at baseline and at follow-up,

lack of comparison groups, and inappropriate statistical analysis were observed.

Seven RCTs were detected. Two studies (Straker et al. 2004; van der Molen et al. 2005b)

were not included because they did not have musculoskeletal health or psychosocial

factors at work as outcomes. Finally, three of the five RCTs were cluster randomized

studies (one being still conducted), and two were individually randomized. Only two

studies were organizational interventions specifically on mental health and psychosocial

job conditions. The contents of the PE interventions are briefly described below. A more

detailed summary of the reviewed original PE intervention studies and their results are

presented in Table 2.

Non-randomized controlled before-after studies

Kobayashi et al. (2008) examined the effects of a participatory organizational intervention

on job stressors and mental health among workers in a manufacturing company. A work

environment improvement team supported each participating department throughout the

six-month intervention. A checklist called the Mental Health Action Checklist for a Better

Workplace Environment (MHACL) was designed for use in a group-based workshop that

was arranged in the departments. In the workshops, workers were informed about stress

and mental health at work and concepts related to improving work environments. Based

on the MHACL, each group listed action items that might be useful for better worker

mental health in their department. The team encouraged the implementation of the plans in

each department after the workshops. Among women, skill underutilization, supervisor

and co-worker support, psychological distress and job satisfaction developed significantly

more favorably in the intervention group than in the control group. No such effect was

observed among men, and no effect was observed on the number of sick leaves in either

gender.

The group of Laing studied the effectiveness of a PE intervention in reducing worker pain

severity through changes aimed at reducing physical demands (Laing et al. 2005) and

improving communication and the psychosocial work environment (Laing et al. 2007) in

40

an automotive parts manufacturing factory. An ergonomics change team (ECT) was

responsible for identifying the targets for ergonomic improvements and developing and

implementing solutions based on the PE Blueprint (identification, assessment of

ergonomic risk factors, solution building/testing, and implementation). The researchers

supported the activities of the ECT during an 11-month period (1 month training, 10

months intervention). The ECT was trained to take into account basic anatomy, physical

and psychosocial risk factors, and ergonomics principles and assessments tools. The

intervention had no significant effect on the workers' mechanical exposures, perceived

effort, perceptions of decision latitude, or pain severity levels. Communication dynamics

regarding ergonomics was significantly enhanced in the intervention group compared to

the control group.

The study of Rivilis et al. (2006) conducted in a depot of a large courier company shared

similarities with the study of Laing et al. An ECT was responsible for the 14-month

intervention that was based on the PE Blueprints. The ECT was trained in ergonomics,

workplace risk factors, and the tools needed to perform ergonomic assessments. Greater

participation in the intervention process was associated with increased levels of job

influence and communication. Improvements in communication were associated with

reduced pain intensity and improved work role function. The lower levels of pain post-

intervention were related to greater work role function.

Evanoff et al. (1999) studied the effect of a PE team on rates of injury, lost time and

MSDs among hospital orderlies. They also hypothesized that direct worker participation in

problem-solving would improve job satisfaction. The PE team received training in team

building, risk identification and control, and undertook supervised exercises in observation

and measurement. The PE team was responsible for identifying and prioritizing safety

problems and implementing solutions. The primary safety intervention implemented was

the development of standardized lifting techniques. All of the orderlies received training

on the standardized procedures according to a lifting manual written by the team. New

employees were required to complete the training before being allowed to work

independently. The rates of injuries and lost days decreased following the two- year

intervention. At the 15-month follow-up, there were significant reductions in the

proportion of employees who reported MSDs. Statistically significant improvements were

41

observed in job satisfaction, perceived job stressors and social support among the

orderlies. However, based on the presented results, it is not clear whether there were any

significant differences between the intervention and control group.

Randomized controlled trials

The aim of the CRT concucted by Tsutsumi et al. (2009) was to study the effect of a

participatory intervention for workplace improvement on mental health and job

performance among blue collar workers manufacturing electronic equipment. The

intervention process lasted approximately 15 months. The intervention consisted of a half-

day training workshop for facilitators of participative actions at their workplaces. The

facilitators received information on mental health and the participatory approach for stress

prevention. Supervisors were educated on the significance of positive mental health and

improvement in the work environment, and given examples of good practices. The

supervisors were trained to identify occupational stressors and to make suggestions for

ways to reduce conflicts and to eliminate the sources of stress. In a workshop, the

intervention group workers were provided with an introduction to the methodology for

improving the work environment, and a lecture on hazard identification. They had group

discussions on work improvements and presentations of action plans. During the 5- month

implementation phase, two follow-up workshops were arranged. Mental health remained

at the same level in the intervention group, but deteriorated in the control group. Job

performance increased statistically significantly in the intervention group compared to the

control group. However, after imputation of missing values, no statistically significant

differences between the groups were observed.

The effect of a one-year PE program on MSDs and individual coping, job demands, job

control and social support was studied in a CRT among operators in the aluminium

industry (Morken et al. 2002). Three intervention groups, 'shift group with supervisor',

'shift group without supervisor', and 'managers only', were formed. The PE program

consisted of 10 didactic sessions (1h 15 min) and discussion (45 min) chaired by a

physiotherapist acquainted with ccupational health services in the aluminum plants. Each

session had a different topic related to physical, psychosocial, work-organizational, and

individual risk factors of MSDs, basics of ergonomics, and coping with MSDs. Active

participation of the group members responsible for identifying, prioritizing and

42

implementing solutions was emphasized. The implemented changes focused on redesign

of workplace, working aids or tools, reducing repetitive-motion stress points and

modifying the work processes to promote job variation. No significant changes on MSDs

were found. Operators in the 'shift group without a supervisor' used coping strategies more

often and social support improved slightly. Job demands and control did not differ

between the groups.

Two individually randomized trials were targeted at the ergonomics of office work

involving VDU. Ketola et al. (2002) evaluated the effect of an intensive ergonomics

approach and education. In the intensive ergonomics group, two physiotherapists visited

each worker and introduced an ergonomic checklist for VDU work. The workers assessed

independently their workstations with the aid of the list. Potential improvements based on

the workers own views and the physiotherapist's observations were discussed. The

workers were encouraged to participate actively in the redesign in their workstations.

Advice to take care of their work postures and to add short pauses into work was given. In

the education group, in the 1-hour training session, the workers were instructed on the

principles of VDU work, they received the same checklist, and were encouraged to

evaluate their own workstation and implement the changes. The same advice considering

work postures and pauses during the work was given. The control group received only a

one-page leaflet. The intensive ergonomics and ergonomic education groups showed less

musculoskeletal discomfort than the control group after a two-month follow-up. No

significant differences in the strain level or in pain or any long-term effects on discomfort,

strain, or pain were found at the 10-month follow-up.

In Bohrs' study (2000), the control group had no education session. The traditional group

had a 1-hour education session consisting of a lecture and informational handouts about

office ergonomics. The participatory education group received a 2- hour education session

with similar content but incorporating discussion, problem-solving exercises, and

evaluation and modification of work areas according to the information received. In

follow-ups at three, six and 12- months, those who received education reported less

pain/discomfort or psychosocial stress than those in the control group, but there was no

indication that the differences were related to better work area configuration or improved

worker postures. The workers in the participatory group reported a better health status than

43

those in the control or the traditional education group. Later Bohr (2002) reported that

there was no evidence that the PE method was more effective than the traditional method

in encouraging the workers to optimize the positions of their work equipment or to

maintain good working postures.

A large CRT ('Stay@Work') aimed to investigate the effectiveness of a PE to prevent LBP

and neck pain among blue and white collar workers is underway in the Netherlands

(Driessen et al. 2008). The intervention group is participating in a six-step PE programme.

A working group was created including eight workers, a representative of the

management, and an occupational and health and safety coordinator. During a one-day

meeting, the working group followed the steps of the PE program and identified the most

important risk factors, the most fundasmental ergonomic measures on the basis of group

consensus, and prepared the implementation plan. If needed, a second meeting could be

arranged to evaluate the status of the implementation phase. The results are expected in

2010.

In summary, there is little evidence for the effectiveness of preventive ergonomics

interventions. The physical and organizational ergonomics interventions do not seem to be

more effective than interventions including no ergonomics. However, the amount of high-

quality studies is insufficient to allow any final conclusions to be drawn. Evidence of the

effectiveness of PE is lacking since most studies suffer from methodological flaws and

only a few RCTs exist.

Tabl

e 2.

Eff

ects

of p

artic

ipat

ory

ergo

nom

ics i

nter

vent

ions

on

mus

culo

skel

etal

dis

orde

rs (M

SDs)

and

psy

chos

ocia

l fac

tors

at w

ork

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ p

sych

osoc

ial

fact

ors a

t wor

k

Tota

lIn

terv

entio

nC

ontro

lN

on-r

ando

mize

d co

ntro

lled

trial

s

*Kob

ayas

hi, 2

008;

Japa

n,m

anuf

actu

ring

ente

rpris

e

Bef

ore-

afte

rw

ith c

ontro

lgr

oup

1434

wor

kers

from

45

depa

rtmen

ts.

Pre-

post

inte

rven

tion

mat

ched

ques

tionn

aire

n=10

71

n= 3

21w

orke

rsfr

om 9

depa

rtmen

ts

n=75

0w

orke

rsfr

om 3

6de

partm

ents

Pre-

post

ques

tionn

aire

sad

min

iste

red

12 m

onth

sap

art

· Sic

k le

ave

data

wer

eob

tain

ed fr

omth

e co

mpa

nyre

gist

ries

Effe

cts o

f a p

artic

ipat

ory

orga

niza

tiona

lin

terv

entio

n on

the

redu

ctio

n of

job

stre

ssor

san

d th

e en

hanc

emen

t of

the

men

tal h

ealth

wer

est

udie

d

· Am

ong

wom

en, s

kill

unde

rutil

izat

ion

(p=0

.048

),su

perv

isor

(p=0

.000

) and

co-

wor

ker

supp

ort (

p=0.

036)

, psy

chol

ogic

aldi

stre

ss (v

igor

p=0

.026

, dep

ress

ion

p= 0

.010

), jo

b sa

tisfa

ctio

n (0

.043

),an

d he

alth

risk

s (H

R) a

ssoc

iate

dw

ith jo

b st

ress

ors (

tota

l HR

p=0.

000,

HR

ass

ocia

ted

with

job

stra

in p

= 0.

030,

and

HR

ass

ocia

ted

with

wor

ksite

supp

ort p

=0.0

00)

chan

ged

sign

ifica

ntly

in th

ein

terv

entio

n gr

oup.

· Im

prov

emen

ts in

the

outc

omes

wer

e m

ore

prom

inen

t am

ong

depa

rtmen

ts w

ith a

50%

or h

ighe

rpa

rtici

patio

n ra

te in

the

plan

ning

wor

ksho

ps (p

=0.0

00-0

.030

) and

amon

g de

partm

ents

with

50%

or

high

er ra

te o

f im

plem

ente

d vs

.pl

anne

d ac

tions

(p=0

.001

-0.0

39).

Effe

ct si

zes:

not

giv

en· N

o fa

vour

able

eff

ect a

mon

g m

en· N

o ef

fect

on

sick

leav

e am

ong

eith

er g

ende

r

*Lai

ng, 2

005,

2007

; Can

ada,

an

mul

tinat

iona

lau

tom

otiv

e pa

rtsm

anuf

actu

ring

com

pany

Bef

ore-

afte

rw

ith c

ontro

lgr

oup

The

com

plet

e pr

e-po

stm

atch

ed q

uesti

onna

iren

= 83

n =

44A

sist

er p

lant

in th

eco

mpa

ny a

s aco

ntro

l gro

upn

= 39

Pre-

post

ques

tionn

aire

sad

min

iste

red

10 m

onth

sap

art

Effe

ctiv

enes

s of a

PE

inte

rven

tion

1) in

redu

cing

wor

ker

pain

seve

rity

thro

ugh

chan

ges a

imed

at

redu

cing

phy

sical

1)· M

inor

influ

ence

on

mec

hani

cal

expo

sure

s· N

o sy

stem

atic

cha

nges

inpe

rcei

ved

effo

rt or

pai

n se

verit

yle

vels

44

45

Tabl

e 2

(con

tinue

d)

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ps

ycho

soci

alfa

ctor

s at w

ork

Tota

lIn

terv

entio

nC

ontro

lde

man

ds (2

005)

2) in

impr

ovin

gco

mm

unic

atio

n(e

rgon

omic

s-re

late

d an

dov

eral

l) an

d ps

ycho

soci

alw

ork

envi

ronm

ent

(dec

isio

n la

titud

e,in

fluen

ce) (

2007

)

2)· C

omm

unic

atio

n dy

nam

ics

rega

rdin

g er

gono

mic

s w

asen

hanc

ed in

the

inte

rven

tion

grou

p(p

= 0

.004

-0.0

45 fo

r all

5qu

estio

ns).

No

diffe

renc

es b

etw

een

the

grou

ps w

ere

obse

rved

for t

he 2

ques

tions

on

over

all w

orkp

lace

com

mun

icat

ion

dyna

mic

s (be

twee

nla

bour

and

man

agem

ent a

ndbe

twee

n on

e an

d hi

s/he

r co-

wor

kers

).Ef

fect

size

s: n

ot g

iven

· No

stat

istic

ally

sign

ifica

ntdi

ffer

ence

s in

deci

sion

latit

ude

orin

fluen

ce

*Riv

ilis,

2006

;C

anad

a,a

cour

ier c

ompa

ny

Bef

ore-

afte

rw

ith c

ontro

lgr

oup

The

com

plet

e pr

e-po

stm

atch

ed q

uesti

onna

iren

= 12

2

one

depo

tn

= 71

a ne

arby

dep

otin

the

sam

ere

gion

as a

cont

rol g

roup

n =

51

Pre-

post

ques

tionn

aire

sad

min

iste

red

14 m

onth

sap

art

· At b

asel

ine,

inte

rven

tion

grou

p w

orke

rsw

ere

anav

erag

e 5.

2ye

ars o

lder

(p=

0.02

89)

and

expe

rienc

edm

ore

pain

(p=0

.021

) tha

n

· Eva

luat

ion

of a

PE

inte

rven

tion

aim

ed a

tim

prov

ing

mus

culo

skel

etal

hea

lth;

A h

ypot

hesi

s tha

t with

grea

ter p

roce

ssim

plem

enta

tion

inte

nsity

,gr

eate

r cha

nge

inex

posu

re to

MSD

risk

fact

ors w

ould

be

obse

rved

and

resu

lt in

impr

ovem

ents

in h

ealth

outc

omes

· Gre

ater

par

ticip

atio

n in

the

proc

ess w

as a

ssoc

iate

d w

ithin

crea

sed

leve

ls o

f job

influ

ence

(p=

0.00

6) a

nd c

omm

unic

atio

n(p

= 0.

094)

· Im

prov

emen

ts in

com

mun

icat

ion

leve

ls w

ere

asso

ciat

ed w

ith re

duce

dpa

in in

tens

ity (p

= 0.

008)

and

impr

oved

wor

k ro

le fu

nctio

n(W

RF,

how

muc

h of

tim

e at

wor

k is

limite

d by

mus

culo

skel

etal

pai

n,p=

0.02

5)· L

ower

leve

ls o

f pai

n po

st-

inte

rven

tion

wer

e re

late

d to

gre

ater

WR

F (p

= 0.

050)

46

Tabl

e 2

(con

tinue

d)

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ps

ycho

soci

alfa

ctor

s at w

ork

Tota

lIn

terv

entio

nC

ontro

lth

e w

orke

rs in

the

cont

rol

grou

p. A

gean

d ba

selin

epa

in le

vel

wer

e ta

ken

into

the

anal

yses

· Mea

sure

s/ou

tcom

es;

perc

eive

d ph

ysic

alde

man

ds, w

ork

orga

niza

tiona

l ris

kfa

ctor

s (pe

rcep

tions

of

job

influ

ence

,co

mm

unic

atio

ndy

nam

ics)

, sel

f-re

porte

dpa

in/d

isco

mfo

rt an

dw

ork

func

tion

outc

omes

Effe

ct si

zes:

not

giv

en

*Eva

noff

, 199

9;U

SA,

hosp

ital o

rder

lies

Pros

pect

ive

inte

rven

tion

trial

(bef

ore-

durin

g-af

ter)

Mea

n em

ploy

men

t dur

ing

stud

y pe

riod

100-

110

orde

rlies

67 o

rder

lies

pre-

inte

rven

tion

and

88 p

ost-

inte

rven

tion

com

plet

edqu

estio

nnai

re

Oth

er h

ospi

tal

wor

kers

use

das

aco

ncur

rent

cont

rol

· 1 m

onth

· 7 m

onth

s· 1

5 m

onth

s· 2

4 m

onth

s

·The

aim

was

to st

udy

ifth

e im

plem

enta

tion

of a

PE te

am w

ould

resu

lt in

low

er ra

tes o

f inj

ury,

lost

time

and

mus

culo

skel

etal

sym

ptom

s (m

ean

body

com

fort

rate

, 1=u

ncom

-fo

rtabl

e, 5

= co

mfo

rtabl

e)·It

was

hyp

othe

size

d th

atdi

rect

wor

ker p

artic

ipa-

tion

in p

robl

em so

lvin

gw

ould

impr

ove

job

satis

fact

ion

(thre

esu

mm

ary

scal

es; t

he Jo

bSa

tisfa

ctio

n Sc

ale

(3ite

ms)

, the

Wor

k A

pgar

(soc

ial s

uppo

rt,in

fluen

ce, 7

item

s), a

ndth

e Ps

ycho

soci

alSt

ress

ors s

cale

(3 it

ems)

· In

the

inte

rven

tion

grou

p,de

crea

sed

risks

of w

ork

inju

ry(R

R =

0.50

, 95%

CI 0

.35-

0.72

), lo

sttim

e in

jury

(RR

=0.2

6, 9

5% C

I0.

14-0

.48)

and

inju

ry w

ith 3

or

mor

e da

ys o

f tim

e lo

ss (R

R=

0.19

,95

% C

I 0.0

7-0.

53).

Tota

l los

t day

sde

clin

ed fr

om 1

36 to

23

annu

ally

per 1

00 fu

ll-tim

e w

orke

req

uiva

lent

s (FT

E).

· In

the

inte

rven

tion

grou

p, m

ean

disc

omfo

rt ra

ting

chan

ged

from

3.5

to 3

.9, p

<0.0

5 ne

ck; 3

.0 to

3.4

, p<

0.01

low

er b

ack;

3.7

to 4

.0 p

< 0.

01fo

rear

m; 3

.3 to

3.8

, p<0

.05

knee

.B

ased

on

the

pres

ente

d re

sults

, it i

sno

t cle

ar w

heth

er th

ere

wer

est

atis

tical

ly si

gnifi

cant

eff

ects

betw

een

the

grou

ps.

· In

the

inte

rven

tion

grou

p,im

prov

emen

ts in

job

satis

fact

ion

(fro

m 7

.7 to

8.8

, p<0

.01)

, in

wor

kA

pgar

(fro

m 1

4.6

to 1

5.8,

p<0

.05)

,an

d in

per

ceiv

ed p

sych

osoc

ial

47

Tabl

e 2

(con

tinue

d)

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ps

ycho

soci

alfa

ctor

s at w

ork

Tota

lIn

terv

entio

nC

ontro

l

Rand

omize

d co

ntro

lled

trial

s

stre

ssor

s (fro

m 8

.2 to

7.2

, p <

0.01

).B

ased

on

the

pres

ente

d re

sults

, it i

sno

t cle

ar w

heth

er th

ere

wer

est

atis

tical

ly si

gnifi

cant

eff

ects

betw

een

the

grou

ps.

*Drie

ssen

, 200

8;Th

e N

ethe

rland

s,bl

ue a

nd w

hite

colla

r wor

kers

of

four

Dut

chco

mpa

nies

·Stu

dy(S

tay@

Wor

k)un

der w

ay

A c

luste

r-ra

ndom

ized

cont

rolle

dtri

al

· Inc

lusi

on c

riter

ia: 1

)age

d 18

-65

y 2

) no

cum

ulat

ive

sick

leav

epe

riod

long

er th

an 4

wee

ks d

ue to

LB

P or

nec

k pa

in in

the

past

3m

onth

s bef

ore

the

start

of th

e in

terv

entio

n 3)

not

pre

gnan

t·5

759

wor

kers

wor

king

at 3

6 de

partm

ents

wer

e ex

pect

ed to

parti

cipa

te a

t bas

elin

e· T

he d

epar

tmen

ts c

onsi

stin

g of

abo

ut 1

50 w

orke

rs w

ere

pre-

stra

tifie

d an

d ra

ndom

ized

· Bas

ed o

n po

wer

ana

lysi

s (IC

C 0

.73,

pow

er 0

.80,

� 0

.05,

25%

decr

ease

bet

wee

n th

e co

mpa

red

grou

ps) 1

662

wor

kers

wou

ld b

ene

eded

(Abo

ut 2

4-36

dep

artm

ents

with

831

wor

kers

/ gr

oup)

·Exp

ectin

g a

drop

-out

rate

of 2

0%, a

n in

itial

sam

ple

of 2

076

wor

kers

wou

ld b

e ne

eded

.

· 6 m

onth

s· 1

2 m

onth

s· D

ata

on th

epr

imar

you

tcom

es,

inte

nsity

of

pain

, sic

kle

ave,

wor

kpr

oduc

tivity

,an

d he

alth

care

cos

ts a

reco

llect

edev

ery

3m

onth

s

The

stud

y w

illin

vest

igat

e th

e (c

ost)

effe

ctiv

enes

s of

PE to

prev

ent L

BP

and

neck

pain

Res

ults

are

exp

ecte

d in

201

0· P

rimar

y ou

tcom

e: a

n ep

isod

e of

LBP

and

neck

pai

n· S

econ

dary

out

com

es: a

ctua

l use

of

ergo

nom

ic m

easu

res,

phys

ical

wor

kloa

d, p

sych

osoc

ial w

orkl

oad,

inte

nsity

of p

ain,

gen

eral

hea

lthst

atus

, sic

k le

ave

and

wor

kpr

oduc

tivity

· Cos

t-eff

ectiv

enes

s ana

lysi

s will

be

perf

orm

ed fr

om th

e so

ciet

al a

ndco

mpa

ny p

ersp

ectiv

e

*Tsu

tsum

i, 20

09;

Japa

n, b

lue-

colla

rw

orke

rsm

anuf

actu

ring

elec

troni

ceq

uipm

ent

A c

luste

r-ra

ndom

ized

cont

rolle

dtri

al

n =

11 a

ssem

bly

lines

n =

97 w

orke

rsn=

6 li

nes

n =

47 w

orke

rsn=

5 li

nes

n= 5

0 w

orke

rsA

ppro

xim

ate-

ly 1

2 m

onth

sTo

exp

lore

the

effe

ct o

f apa

rtici

pato

ry in

terv

entio

nfo

r wor

kpla

ce im

prov

e-m

ent o

n m

enta

l hea

lthan

d jo

b pe

rform

ance

· Gen

eral

Hea

lthQ

uest

ionn

aire

(GH

Q)

and

Hea

lth a

nd W

ork

Perf

orm

ance

Que

stio

nnai

re (H

PQ)

· GH

Q sc

ores

rem

aine

d at

the

sam

ele

vel i

n th

e in

terv

entio

n gr

oup,

but

dete

riora

ted

in th

e co

ntro

l gro

up· H

PQ sc

ores

incr

ease

d in

the

inte

rven

tion

grou

p, b

ut d

ecre

ased

inth

e co

ntro

l gro

up (p

= 0

.048

). A

fter

impu

tatio

n of

mis

sing

val

ues,

ther

ew

as n

o st

atis

tical

ly si

gnifi

cant

diffe

renc

e be

twee

n th

e gr

oups

.·E

ffect

size

: not

giv

en

48

Tabl

e 2

(con

tinue

d)

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ps

ycho

soci

alfa

ctor

s at w

ork

Tota

lIn

terv

entio

nC

ontro

l

*Mor

ken,

200

2;N

orw

ay,

alum

iniu

m in

dust

ry

A c

luste

r-ra

ndom

ized

cont

rolle

dtri

al

All

wor

kers

from

8 p

lant

sco

mpl

eted

the

ques

tionn

aire

.B

asel

ine

n=56

54, f

ollo

w-u

pn=

5143

, mat

ched

n=

3321

,n=

95

grou

psn=

218

1 op

erat

ors

Wor

kers

from

the

prod

uctio

nlin

e w

ere

rand

omiz

ed

n= 4

0 gr

oups

,n=

414

oper

ator

s

3 In

terv

entio

ngr

oups

(I):

I1) '

shift

gro

upw

ith su

perv

isor

'(n

=20

grou

ps o

fop

erat

ors &

supe

rvis

ors,

n=

132

oper

ator

s)I2

) 'sh

ift g

roup

with

out

supe

rvis

ors'

(n=1

8 gr

oups

of

oper

ator

s onl

y,n=

135

)I3

) 'm

anag

ers

only

', (n

= 2

grou

ps o

fsu

perv

isor

s &m

anag

ers a

nd10

gro

ups o

fop

erat

ors

n= 1

47)

n =

55 g

roup

sn=

176

7op

erat

ors

Con

trol g

roup

A (C

A)

n= 5

5 gr

oups

n= 4

23op

erat

ors

Con

trol g

roup

B (C

B)

From

oth

erpa

rts o

f the

sam

e pl

ant,

n=1

344

oper

ator

s,no

n ra

ndom

i-ze

d

16 m

onth

sEx

amin

atio

n of

the

effe

cts

of a

1-y

ear P

E pr

ogra

m o

nM

SDs,

copi

ng st

rate

gies

,jo

b de

man

ds, c

ontro

l and

soci

al su

ppor

t

· MSD

s inc

reas

ed in

the

CB

(sho

ulde

rs p

=0.0

14; h

ands

p<0.

001;

elb

ows p

<0.0

01).

No

stat

istic

ally

sign

ifica

nt c

hang

esin

the

othe

r gro

ups.

The

chan

gedi

d no

t diff

er st

atis

tical

lysig

nific

antly

bet

wee

n th

ein

terv

entio

n an

d co

ntro

l gro

ups.

· The

inte

rven

tion

grou

ps u

sed

mor

e co

ping

stra

tegi

es th

anco

ntro

l gro

ups (

p=0.

043)

. I2

('ope

rato

rs w

ithou

t asu

perv

isor

s') in

crea

sed

the

mos

t(m

ean

chan

ge=0

.041

, 95%

CI

0.00

5-0.

077)

. I2

and

CB d

iffer

ed(p

=0.0

17).

Soci

al su

ppor

t in

the

I2 im

prov

ed sl

ight

ly fr

om p

re to

post

. All

othe

r gro

ups t

ende

d to

decl

ine

(p=0

.10)

. Job

dem

ands

and

cont

rol d

id n

ot d

iffer

stat

istic

ally

sign

ifica

ntly

.·E

ffect

size

: not

giv

en

49

Tabl

e 2

(con

tinue

d)

Firs

t aut

hor

Yea

rIn

dust

ry/s

ecto

r

Stud

y de

sign

Parti

cipa

nts

Follo

w-u

pIn

terv

entio

n/ A

imEf

fect

s on

MSD

s/ps

ycho

soci

alfa

ctor

s at w

ork

Tota

lIn

terv

entio

nC

ontro

l

Ket

ola,

200

2;Fi

nlan

d,m

unic

ipal

offi

cew

orke

rs u

sing

vide

o di

spla

y un

its

A rand

omiz

edco

ntro

lled

trial

n =

124

Inte

rven

tion

grou

ps:

1) in

tens

ive

ergo

nom

ics

grou

p, n

= 37

2) e

duca

tion

grou

p, n

= 35

n= 3

9· 2

mon

ths

·10

mon

ths

Eval

uatio

n of

the

effe

ct o

fan

inte

nsiv

e er

gono

mic

appr

oach

and

edu

catio

n on

wor

ksta

tion

chan

ges a

ndM

SDs (

disc

omfo

rt, st

rain

pain

).

· At 2

mon

ths f

ollo

w-u

p, in

the

inte

nsiv

e vs

. con

trol g

roup

,si

gnifi

cant

(p=0

.001

-0.0

25)

redu

ctio

n in

disc

omfo

rt in

the

neck

(mea

n 2.

7 vs

. 3.3

), ar

eabe

twee

n ne

ck a

nd sh

ould

er(r

ight

side

) (2.

5 vs

. 3.1

),sh

ould

ers (

2.2

vs. 2

.8 ri

ght,

1.9

vs. 2

.4 le

ft), r

ight

fore

arm

(2.1

vs. 2

.5),

left

finge

rs (1

.8 v

s.2.

3), a

nd u

pper

bac

k (2

.2 v

s.2.

9). I

n th

e ed

ucat

ion

grou

p,si

mila

r cha

nges

(p=

0.00

2-0.

009)

exc

ept s

houl

ders

. At 1

0m

onth

s fol

low

-up,

no

stat

istic

ally

sign

ifica

nt c

hang

esw

ere

dete

cted

in b

oth

grou

psco

mpa

red

to c

ontro

l gro

up in

disc

omfo

rt, st

rain

or p

ain.

·Effe

ct si

ze: n

ot g

iven

*Boh

r, 20

00; S

t.Lo

uis M

isso

uri,

USA

,re

serv

atio

nce

nter

/off

ice

(usi

ngm

ostly

com

pute

r)

A rand

omiz

edco

ntro

lled

trial

Subj

ects

wer

e se

lect

ed a

tra

ndom

from

a li

st o

fvo

lunt

eers

who

wer

eem

ploy

ed a

s age

nts a

t the

cent

raliz

ed re

serv

atio

n, u

sed

com

pute

rs a

t lea

st 5

h p

erw

ork

day

n= 1

54 a

t bas

elin

en=

124

at th

e 12

mon

ths

2 in

terv

entio

ngr

oups

:1)

trad

ition

aled

ucat

ion,

n=39

2) p

artic

ipat

o-ry

edu

catio

nn=

38

n= 4

7· 3

mon

ths

· 6 m

onth

s· 1

2 m

onth

s

Inve

stig

atio

n of

the

effic

acy

of w

orke

r edu

catio

npr

ogra

ms i

n pr

even

ting

MSD

s· P

ain/

disc

omfo

rt in

the;

uppe

r bod

y (s

core

s inc

lude

dsy

mpt

oms f

or n

eck,

upp

erba

ck, s

houl

der/u

pper

arm

,fo

rear

m, a

nd w

rist/

hand

)an

d lo

wer

bod

y (lo

wer

bac

k,hi

p/bu

ttock

s, kn

ees,

and

feet

/ank

le)

· Psy

chos

ocia

l wor

k st

ress

(6ite

ms)

· Upp

er b

ody

scor

e: c

ontro

lgr

oup

repo

rted

high

er fr

eque

ncy

of p

ain/

disc

omfo

rt th

roug

hout

the

stud

y th

an e

ither

inte

rven

tion

grou

ps[F

(2,1

51) =

4.8

6, p

<0.0

1)] N

ost

atis

tical

ly si

gnifi

cant

diff

eren

ce b

etw

een

tradi

tiona

lan

d pa

rtici

pato

ry e

duca

tion

grou

p.· L

ower

bod

y sc

ore:

no

stat

istic

ally

sign

ifica

ntdi

ffere

nce

acro

ss th

e gr

oups

.

50

2.5. Kitchen work as a target of an ergonomics intervention

The present study was targeted to kitchen work. Kitchen workers are mainly women and

they suffer a high prevalence of MSDs (Huang et al. 1988; Ono et al. 1997; Ono et al.

1998; Perkiö-Mäkelä et al. 2006; Nagasu et al. 2007; Shiue et al. 2008). The work is

physically demanding (Shibata et al. 1991; Ono et al. 1997; Ono et al. 1998) and it often

involves ergonomic problems (Huang et al. 1988; Shibata et al. 1991). The HORECA

sector (hotels, restaurants, catering) employs about eight million people in the European

Union. In 2000, almost 55% of the EU-15 workers in the sector reported that their job

involved painful or tiring positions compared to 45% across all sectors. The corresponding

figures for carrying or moving heavy loads were 43% compared to 36%, and for repetitive

hand or arm movements 64% compared to 56% overall. Pain in lower limbs is more

common in the HORECA sector than elsewhere (European Agency for Safety and Health

at Work 2008).

In a large Japanese cross-sectional survey among cooks (n= 5835) working in school

lunch services, the prevalence of LBP and its associations with various risk factors were

recently examined (Nagasu et al. 2007). About 83% of the workers were women (mean

age 48 years). Female gender was associated with LBP [prevalence ratio, (PR) 1.3].

Several other factors were significantly associated with the prevalence of LBP. In women,

these included no regular physical activity, the number of hours of sleep � 7, and the

number of prepared lunches per cook. In both genders, current and past smoking, lack of

breaks in the morning session, physical kitchen environment (noisy surroundings, poor

state of drainage, presence of slippery surfaces, bumps and obstacles on the floor), and the

height of cooking equipment (e.g. counter-tables, kitchen sinks, cauldrons) were

associated with LBP. In addition, job dissatisfaction, stress at work, financial constraints,

health-related stress, and worries about the future were similarly associated. The PR

values varied from 1.1 to 1.7, being strongest for stress at work (PR 1.7), and current (PR

1.6) and past (PR 1.4) smoking. The annual incidence of MSDs among Chinese restaurant

cooks (n= 52 261) was observed to be higher (ORs 1.3-1.4) compared to the age and sex

matched general population. There was a trend for increasing MSD incidence with age in

both the cooks and the reference group (Shiue et al. 2008).

51

In one considers municipal occupations in Finland, then the kitchen workers are among

the top five occupations with the highest sickness absence and disability pension rates

(Forma 2004; Vahtera et al. 2008) as well as reporting high physical work load and fast

work pace, unsatisfactory working climate, poor perceived health, low correspondence

between knowhow and work, need for education, and fear of temporary dismissals or lay-

offs (Forma 2004). In the planning phase of the present intervention study, kitchen

workers were considered to represent good subjects for ergonomic improvements. Based

on observations in kitchens during the development phase of the study, many generic risk

factors for MSDs were observed. Awkward postures, repetitive and forceful movements,

and manual material handling typically occurred often in the daily routine. The work

imposed both static and dynamic load on the musculoskeletal system. The workers

performed several parallel tasks, they worked under time pressure and high mental and

physical workloads. In the study, seven main work tasks were distinguished: preparation

(e.g. washing, paring, and cutting of the groceries), cooking and baking, distribution and

serving of the food (e.g. dishing out and dosage of the food), dishwashing (e.g. sorting,

pre-washing and washing of the dirty dishes/ sorting and setting of the clean dishes),

cleaning and maintenance of room and equipment (e.g. cleaning tables and floors,

handling and transit of refuses), and receiving and storing of raw material. Packing food

into thermal transport cases was an extra task in kitchens which prepared the food to be

transported to other kitchens where the food was delivered to the clients.

Little previous research had focused on this challenging occupational group. Kitchens

were also the correct sized units suitable for a cluster randomized design. In particular,

municipal kitchens were thought to be sustaining workplaces that would allow a long

enough follow-up without an immediate threat to their continuing existence.

52

3. THEORETICAL FRAMEWORK OF THE STUDY

There are several theoretical models describing the multifactorial etiology of MSDs

(Huang et al. 2002; Karsh 2006). These are needed to target interventions that might

prevent or reduce MSDs. The theories also guide in the selection of variables that should

be controlled for in a study. The theoretical basis of this thesis (Figure 1) is based on the

ecological model of Sauter and Swanson (1996) that was also the framework of the entire

ERGO-study. This model, originally designed for office and VDU work, incorporates

biomechanical, psychosocial and cognitive factors, the last of these three components

being the one distinguishing it from the other models. According to this model, MSDs are

related to work technology that includes workplace characteristics, and the nature of work

processes and tools. The work technology is linked directly to physical work demands, as

defined by the physical connection between a tool and a worker, and to the work

organization. The pathway from the work organization to the physical demands proposes

that the physical demands of work are affected by organizational demands; for example,

increased repetition may be caused by increased specialization of work tasks. A direct path

is seen also between the work organization and psychosocial strain which can then affect

the biomechanical strain. The model suggests that the relationships between

biomechanical strain and the development of MSDs are mediated by complex cognitive

processes that involve the detection and sensation of symptoms and their attribution to the

musculoskeletal system. The work organization, psychological strain, and individual

factors have an influence on the connection between biomechanical strain and MSDs, and

on the manner by which workers detect and respond to physical sensations. Finally, the

model shows the reciprocal links between MSDs and the work organization and

psychological strain.

Study hypotheses based on the theoretical framework

It was hypothesized that by implementing ergonomics changes in tools, equipment and

technology aimed at optimisation of biomechanical and mental load and affecting factors

related to work organization, it would be possible to prevent MSDs and to improve the

psychosocial work environment among kitchen workers (I-II). At baseline, before the

intervention started, kitchen workers were assumed to have a high occurrence, not only of

53

single-site pain, but also of pain at multiple anatomical sites (III). In study IV, there were

two hypotheses assuming opposite time sequences: that psychosocial factors at work and

mental stress would predict the occurrence of MSP, and that MSP would predict the

occurrence of psychosocial factors at work and mental stress.

Figure 1. Framework of the study based on the conceptual model of work-relatedmusculoskeletal disorders, adapted from Sauter and Swanson 1996. Boxes with dash lines referto the measures used in the current study.

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54

4. AIMS OF THE STUDY

The primary aim was to study the efficacy of a workplace PE intervention in preventing

MSDs among municipal kitchen workers. Second, the effects of the PE intervention on

psychosocial working conditions as intermediate outcomes were studied. Furthermore, the

occurrence of MSP and the associations between MSP and psychosocial factors at work

over time were examined.

The specific aims were:

1. To study the efficacy of a PE intervention in preventing MSDs (I).

2. To investigate the effects of a PE intervention on psychosocial factors at work as

intermediate outcomes of the intervention (II).

3. To examine the co-occurrence of musculoskeletal pain in seven distinct body sites

and their combinations in female kitchen workers (III).

4. To identify the developmental patterns of MSP and of psychosocial factors at work

during a two-year follow-up period. To study the interrelationships between

psychosocial factors at work and MSP in female kitchen workers (IV).

55

5. MATERIALS AND METHODS

5.1. General description of the study

The sub-studies comprising this dissertation are part of a larger research programme

carried out by the FIOH during the years 2002-2005 in collaboration with municipal

kitchens in four large cities in Finland. The Academy of Finland (Health Promotion

Research Programme), the Finnish Work Environment Fund, the Ministry of Labour, and

the Local Government Pensions Institution financially supported the study. The Ethics

Committee of the FIOH approved the study proposal.

At the beginning of the study, meetings were arranged in each city where the management

and kitchen workers were informed about the project and encouraged to participate. First,

meetings with representatives of foodservice management were held in order to obtain

their approval and commitment. Next, information sessions for the workers were held. In

these sessions, the aims of the study and the study protocol were described. A research

agreement was signed with each city and a written informed consent was obtained from

each kitchen and each worker who agreed to participate in the study.

Flow of the study

The flowchart of the study, with the eligibility criteria for participation, is presented in

Figure 2. Altogether 122 kitchens (60% of those eligible) were randomized into

intervention or control groups. Three kitchens dropped out immediately after the

randomization and thus 119 kitchens of schools, nurseries, and nursing homes, with a total

of 504 workers participated in the study. For feasibility reasons, the intervention (n= 59)

and control (n= 60) kitchens were divided into 16 series each including eight kitchens

(four intervention and four control kitchens) on average. The series entered the active

study phase sequentially in time. Within each series, the kitchens of both study arms

proceeded parallely. The first series started in the spring of 2002 and the last ones in the

autumn of 2003. By the end of 2004, the intervention phase was completed. Each series

had a 12-month post- intervention follow-up. The follow-up phase was completed by the

end of 2005.

56

Figure 2. Flowchart of enrollment and study design.* Beginning of the first series. † Beginning of the last series.

5.2. Study designs and subjects

Detailed descriptions of the study designs and study material analyzed in the various sub-

studies are given in Figure 3.

One of the sub-studies was cross-sectional (III) and focused on the co-occurrence of pain

in seven body sites at baseline. Here the subjects were composed of 523 workers from all

the initial 122 kitchens. Only 19 of the workers were men, and therefore the analyses were

restricted to women only (n=504).

Study I describes the effects of a PE intervention on MSDs and study II investigates the

effects on psychosocial factors at work. The subjects at baseline were 504 workers in 119

kitchens. Cross-sectional open sample data were collected at nine time points. The number

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57

of workers participating in different cross-sections, by study arm (59 intervention kitchens

and 60 control kitchens), are seen in Figure 3.

In study IV, the intervention and control groups were pooled together in a two- year

prospective study to investigate developmental patterns of MSP and to examine

associations between MSP and psychosocial factors at work over time. The final study

sample consisted of women with observed values of MSP in at least four time points of

nine (n=385).

Figure 3. Study designs and study materials in the original studies.

*BL; baseline, I; intervention phase, PI; post-intervention follow-up phase.† PIA, post-interventionassessment. Five series finished the intervention at 9 months (I9, n = 157) and 11 series at 12months (I12). The PIA was thus made either at 9 or 12 months after the start of the implementationphase of the intervention (combined n = 452).

5.3. Sample size, randomization and blinding

Since the participants within any cluster are more likely to be similar with each other than

with the participants in another cluster, and also to have more similar outcomes, a larger

sample size is required in a CRT to obtain adequate statistical power compared to an

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58

individually randomized trial. Due to the cluster randomized design, within and between

cluster correlations were considered. Based on power calculations and assumptions

[intraclass correlation (ICC) 0.50, average of three subjects per kitchen, power of 0.80 to

detect a difference of 15% in rates between the groups with � 0.05], the number of

kitchens needed was estimated as 80 per group. Although the final number of kitchens was

smaller, the sample size was sufficient because the ICC in the calculations proved to have

been overestimated. At baseline, the empirical ICCs for the musculoskeletal and

psychosocial work factor outcomes, as well as for perceived physical workload were

below 0.30. The ICCs of workers in the same city area varied from 0.0 to 0.06.

Randomization was based on stratification by area (city district) and type of kitchen

(school, nursery, home for senior citizens, other institution), and an assignment algorithm

(Alternate Ranks Design, ARD) (Bonate 2000). Kitchens in each stratum were ranked in a

descending order by the number of staff. The largest kitchen was randomized first, and

thereafter, the next two were systematically allocated in pairs to the other study arm and so

on. Randomization was carried out by an individual not otherwise involved in the study

during the field phase.

It is impossible to conduct a PE intervention in a blinded manner. However, during

baseline data collection, neither workers participating in the study nor the researchers

knew to which group the workers would be allocated since the randomization was done

after the baseline data collection (Figure 2). The researchers had no access to the

questionnaire data during the data collection, and data analysis was started only after the

follow-up data collection was completed.

5.4. Data collection, worker turnover and loss to follow-up

Data were gathered from questionnaires which a researcher distributed to all participating

kitchens in both study arms. The baseline information (BL) was collected before

randomization and thereafter every three months during the intervention (I3, I6, I9, I12) and

the 12-month post- intervention follow-up period (PI3, PI6, PI9, PI12). Due to summer

holidays at schools, at least one questionnaire was omitted in each kitchen series. Five

series finished the intervention at 9 months (I9, n = 157) and 11 series at 12 months (I12, n

59

= 295). The post-intervention assessment (PIA) was thus made at either 9 or 12 months

after the start of the implementation phase (combined n = 452). The next questionnaire

(PI3) was always three months after the PIA. Extensive questionnaire data were collected

at the BL and after the intervention phase (PIA) and a shorter questionnaire was

distributed every three months during the intervention and the 12-month post-intervention

follow-up period.

Response rates in different surveys varied between 92% and 99%. The proportion of

workers employed in the same kitchen throughout the intervention phase was 86% in the

intervention group and 84% in the control group. The respective values for the 12-month

follow-up were 70% and 71%.

5.5. The participatory ergonomics intervention

The framework of the intervention was based on a model developed at the FIOH

(Leppänen 2001). The intervention process is described in Figure 4. Active group work

was emphasized, and workers were regarded as actors identifying problems, planning and

evaluating changes, and implementing them in collaboration with the management and

technical staff. The researchers provided guidance and support, and facilitated the progress

of the process. The intervention consisted of a 2-month pre-implementation and 9-12-

month implementation phase promoted by eight workshops (28 hours in total). Thus the

duration of the intervention was 11-14 months. In two cities, a local steering group was

established for improving the exchange of information between the research group and

food service management.

The field study was carried out by four teams of two researchers trained in ergonomics

and in good practice in kitchen work. One researcher (ergonomist) was responsible for

supporting the intervention process. The main task of the other researcher was to assess

the state of the ergonomics, to document the implemented changes and to distribute the

questionnaires. Regular meetings were held to ascertain the similarity of working methods

between the research teams. The project coordinator supervised the workshops and

provided feedback to the researchers.

60

The foodservice managers and technical staff were invited to participate in the workshops.

The kitchens were not provided with extra funding in association with the CRT and the

ergonomics changes were implemented within their annual budgets. The municipal

authorities agreed to prioritize the intervention kitchens in case of special needs arising

during the intervention phase.

The control kitchens continued their normal activity. During 3-monthly visits, the

researchers distributed questionnaires and collected information of all spontaneously

implemented ergonomics changes and undertook short interviews. There were no other

contacts with the researchers in these kitchens.

Pre-implementation phase

In the 2-month pre-implementation phase, all staff of the intervention kitchens were

gathered together for two 5-hour workshops. In the first session, the workers were taught

the basics of ergonomics and guided to analyze their work tasks and processes with the

intention of identifying strenuous tasks and risk factors of MSDs. The kitchen staff had

one month's time to continue the work analysis in their own kitchens and develop ideas to

decrease their physical and mental workload. The ergonomist visited each kitchen once

and gave them one supportive phone call. In the second workshop, each kitchen decided

on their primary targets and planned how these would be best implemented.

Implementation phase

During the 9-12 month implementation phase, all staff of the intervention kitchens

convened six times for a 3-hour workshop. Each workshop included a specific theme

related to ergonomics and the progress of the intervention in each kitchen was thoroughly

discussed. The ergonomist visited the kitchens if requested and provided support to the

process. The workshops rotated from one kitchen to another to give the workers an

opportunity to learn from each other's solutions and practices. The personnel of each

kitchen kept a detailed diary about the ergonomic changes made. Based on the diaries, the

researchers carefully recorded all ergonomic changes and evaluated the significance of the

changes with regard to the load on the musculoskeletal system or occupational safety. The

changes were classified according to the work tasks and by target.

61

Figure 4. Intervention process. WS, workshop.

Unconnected organizational reforms

An organizational reform of foodservices occurred simultaneously with the intervention

study in two of the participating cities. In one city, the planning and implementation of the

reform were executed concurrently with the intervention and in one other city, the reform

was planned during the intervention and the new organization started during the 12-month

post-intervention follow-up. In the new model, the major change was that cooking was

centralized to large production kitchens, from which meals were delivered to other

kitchens to be distributed to the clients. In addition, discussions about the possible

outsourcing of the foodservices or organizing them as a public utility were underway in

the two cities. Altogether 31 intervention and 31control kitchens were involved in these

organizational reforms. In study II, that examined the effects of the ergonomics

intervention on psychosocial factors at work, independent and joint effects of the

intervention and organizational reforms were studied in a secondary analysis.

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Unconnected organizational reforms

An organizational reform of foodservices occurred simultaneously with the intervention

study in two of the participating cities. In one city, the planning and implementation of the

reform were executed concurrently with the intervention and in one other city, the reform

was planned during the intervention and the new organization started during the 12-month

post-intervention follow-up. In the new model, the major change was that cooking was

centralized to large production kitchens, from which meals were delivered to other

kitchens to be distributed to the clients. In addition, discussions about the possible

outsourcing of the foodservices or organizing them as a public utility were underway in

the two cities. Altogether 31 intervention and 31control kitchens were involved in these

organizational reforms. In study II, that examined the effects of the ergonomics

intervention on psychosocial factors at work, independent and joint effects of the

intervention and organizational reforms were studied in a secondary analysis.

62

5.6. Measures

5.6.1. Musculoskeletal disorders and multiple-site musculoskeletal pain

Musculoskeletal outcomes were measured by modified questions from the validated

Nordic Musculoskeletal Questionnaire (Kuorinka et al. 1987).

Musculoskeletal pain, trouble caused by pain and sick leave due to any pain during the

past 3 months

The questionnaires contained the following question on musculoskeletal pain in the neck,

shoulders, forearms/hands, low back, hips, knees and ankles/feet: "Have you had 'x' pain

during the past 3 months (no/yes) ?" Trouble and sick leave due to pain were asked

separately for each of the seven anatomical sites by the questions: "Please, assess how

much trouble 'x' pain has caused during the past 3 months (1 = 'not at all', 7 = 'very much'),

and "Have you been on the sick leave due to 'x' pain during the past 3 months (no/yes)?

Localized fatigue after the working day during the past 7 days

Musculoskeletal fatigue was asked by a question: "How much bodily fatigue you have felt

after the working day during the past 7 days (1 = 'not at all', 6 = 'very much').

Multiple-site pain

A sum index (0 = 'no pain', 7 = 'pain in seven sites') was calculated to describe the

occurrence of pain in multiple body sites during the past 3 months. The sum dichotomized

to 0-2 pain sites (no MSP) and � 3 pain sites (MSP) was used as an outcome measure. A

sensitivity analysis was conducted by using 4 � pain sites as the cut-off point. To obtain a

view of concurrent pain in the body, the occurrence of all combinations of the seven

anatomical sites was examined. In addition, the sites were combined to three larger

anatomical areas: the axial (neck and low back), the upper limbs (shoulders,

forearms/hands), and lower limbs (hips, knees, ankles/feet).

63

5.6.2. Psychosocial factors at work and mental stress

Psychosocial factors at work were assessed using questions adapted from a validated

questionnaire (Elo et al. 1992). All items had initially five categories that were

dichotomized to represent the presence or absence of the outcome as shown below.

Mental stress during the past month. "Stress refers to a situation in which a person feels

tense, restless, nervous or anxious, or is unable to sleep at night because his/her mind is

troubled all the time. Have you felt like this during the past month?" (1= not at all, 2= only

a little, 3= to some extent 4= rather much, 5= very much); dichotomized as no (1-3)/ yes

(4-5).

Mental strenuousness of work. "Is your work mentally strenuous?" 1= not at all, 2= rather

light, 3= somewhat strenuous, 4= rather strenuous, 5= very strenuous. Dichotomized as no

(1-3)/ yes (4-5).

Hurry at work. "Do you have to hurry to get your work done?" (1= never, 2= rather

seldom, 3= now and then, 4= rather often, 5= constantly); dichotomized as no (1-3)/ yes

(4-5).

Job dissatisfaction. "How satisfied are you with your present work?" 1= very satisfied, 2=

rather satisfied, 3= neither satisfied nor dissatisfied, 4= rather dissatisfied, 5= very

dissatisfied. Dichotomized as no (1-3)/ yes (4-5).

Poor co-worker relationships. "How do workmates get along at your workplace?" (1=

very well, 2= rather well, 3=neither well nor badly, 4= there are some problems, 5=

badly); dichotomized as no (1-3)/ yes (4-5).

Low job control. "At work, can you influence matters concerning yourself?"

Low skill discretion. "Can you use your knowledge and skills in your work?"

Low supervisor support. "Does your supervisor provide support and help when needed"?

These questions had similar classes (1= very much, 2= rather much, 3= to some extent, 4=

very little, 5= not at all) and were dichotomized as no (1-3) / yes (4-5).

64

5.6.3. Perceived physical workload

The question regarding the perceived physical workload was constructed specifically for

the kitchen work since no suitable published methods for the purpose were available. The

perceived physical workload (1= 'not at all', 7= 'very strenuous') of seven different work

tasks (preparation, cooking and baking, distribution and serving of food, packing food to

be delivered to clients, dishwashing, cleaning and maintenance of room and equipment,

receiving and storing of raw material) was inquired. The mean was used in the analyses.

The use of seven categories was based on the previous findings suggesting that the

minimum number of categories should be between five to seven. In addition, up to seven,

the reliability of the measure increases, but thereafter addition of more categories causes a

decline in the reliability (Streiner and Norman 1995).

5.6.4. Covariates

Job title (foodservice manager, chef, cook, kitchen aid, other), years employed in kitchen

work and employment (permanent, full-time) were characteristics of work history. Age,

gender, height, weight, body mass index (BMI, kg/m2), overweight (no overweight; BMI

< 25/ overweight; BMI � 25 kg/m2), current regular smoking (no/yes), and physical

exercise (� once a week/ > once a week) were other items included. The question

regarding physical exercise was worded as follows: "During the past 12 months, how

many times a week have you exercised at least 20 min per session, to the extent to cause

perspiration?" (not at all, less than once a week, once a week, 2-3 times a week, 4-5 times

a week, 6-7 times a week). A sum index of musculoskeletal pain (0 = 'no pain', 7 = 'pain in

seven sites'), the mean of the perceived physical workload, organizational reforms

(no/yes), study arm (intervention/control group), and city were also considered as

covariates.

Type of kitchen (school, nursery, nursing home, geriatric service centre, other) was used

as a cluster level characteristic.

The variables and their roles as outcomes, determinants or covariates, and statistical

analyses in the original studies are summarized in Table 3.

65

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66

5.7. Statistical analyses

Summary of statistical analyses used in the original studies are presented in table 3. All

analyses were performed using the SAS version 9.1 (SAS Institute Inc., Cary, NC, USA)

and SPSS version 12.0.1 (SPSS Inc., Chicago, IL, USA).


disorders and psychosocial factors at work

In studies I and II, the data were analyzed according to the intention-to-treat principle and

the results were based on prevalence rates or mean scores of cross-sectional data of an

open sample (Ukoumunne and Thompson 2001; Atienza and King 2002). In analyses by

generalized estimating equations (GEE), the clustering of the data (workers, kitchens) was

taken into account.

Assessment of the effects of the intervention was based on the comparison of the

musculoskeletal outcomes between the groups (study arms) at each cross-section. The

effects of covariates (Table 3) on the results were tested at the PIA and at the 12-month

post-intervention follow-up (PI12)). Effects on musculoskeletal fatigue and trouble due to

pain were studied using mixed regression models, in which the kitchen series and

individual kitchens were interpreted as random variables and the study arm, city, and

potential covariates as fixed variables. In logistic regression models, which were used to

analyze the effects on pain and sick leaves, the series and individual kitchens were used as

subject effects. The repeated measures design was used in the re-analyses among the

subgroup of subjects that remained in employed in the same kitchens throughout the study

(cohort analysis,

n = 307).

Between-group differences in psychosocial factors at work were studied at BL, at PIA and

at PI12. The variable assessing the independent and joint effects of the intervention and the

unconnected organizational reforms on psychosocial factors at work was coded as follows:

1=no intervention, no organizational reform; 2= intervention, no organizational reform; 3=

no intervention, organizational reform; 4=intervention, organizational reform. No

67

intervention/ no organizational reform (1) was used as the reference group. Logistic

regression models were first adjusted only for the baseline level of the outcome variable,

and the second models also for other covariates (Table 8 and 9).

In all the models, ORs with their 95% confidence intervals (CI) were estimated as the

measure of effect. Two-sided tests of statistical significance (p < 0.05) were used.

5.7.2. Multiple-site musculoskeletal pain and reciprocal associations with

psychosocial factors at work

The occurrence of MSP at baseline was described in the cross-sectional study (III) among

female workers, who had information on all seven assessed anatomical sites (n= 495,

Figure 3). Differences in pain prevalence between age groups were assessed with the

Mann-Whitney U- test. PRs for pain in one anatomical site relative to another were

calculated using Cox proportional hazards regression. Adjustment was made for

occupational title, age, and work years.

In study IV, the intervention and control groups were pooled to be analyzed prospectively

over two-years (Figure 3). Since the number of men was so low, the analyses were carried

out among women only. The aim was to study associations of psychosocial factors at work

and mental stress with development of MSP over time, as well as associations in the

reversed time order. To assess the average time trends of the prevalence of MSP, a mixed-

effects logistic regression model was fitted to the data with linear time effects.

Associations between MSP and psychosocial factors at work were first studied by a time-

lagged generalized estimation equations model (Liang and Zeger 1986). Repeated

measurements of psychosocial factors were studied in relation to MSP three months later,

and vice versa. Second, a semi-parametric group-based approach (trajectory analysis)

(Nagin 1999; 2005; Jones and Nagin 2007) was used to identify developmental patterns of

MSP and psychosocial factors at work. This method identifies groups (trajectories) of

individuals who tend to have a similar profile over time. The Bayesian information

criterion (BIC) is used as the basis for selecting the optimal model, number of trajectories,

and their shape (intercept, linear trend, cubic or quadratic). Individuals are assigned to the

68

trajectory to which they have the highest probability of belonging. Ideally, the posterior

membership probability should be near 1. To minimize the risk of misclassification, a

model that includes trajectories with mean posterior assignment probabilities below 0.70 is

not recommended (Nagin 2005). Measurements should be available in at least 50% of the

assessed time points to reliably assess group membership probabilities, and in at least

three time points to detect trajectories of quadratic shape (Kokko 2004). Based on these

requirements, women with observed values of MSP in at least four time points of nine

during the two-year follow-up constituted the final data set (n=385, Figure 3). After

definition of the trajectories, associations of the baseline psychosocial factors at work with

MSP trajectories were analyzed and vice versa. Finally, psychosocial work factor

trajectories were studied in relation to MSP trajectories.

Logistic regression models with odds ratios (OR) and 95% confidence intervals (CI) were

used to assess the associations. All models were adjusted for age, BMI, smoking, physical

exercise, and perceived physical workload at baseline, and for the study arm (intervention

/control) and organizational reforms (no/yes). In the reciprocal time-lagged analyses, the

baseline value of the outcome was included among the independent variables.

6. RESULTS

6.1. Effects of the participatory ergonomics intervention in the

prevention of musculoskeletal disorders (I)

6.1.1. Baseline characteristics

At baseline, there were no statistically significant differences in the 3-month prevalence

rates of pain between the intervention and the control group. In both groups, pain was

most common in the neck, low back, and forearms/hands, followed by pain in the

shoulders, ankles/feet, knees and hips. No significant differences between the groups in

the occurrence of MSP, sick leaves, or adverse psychosocial working conditions were

observed. Compared to the control group, somewhat fewer permanent workers and more

69

smokers were assigned to the intervention group. Overall, randomization seemed to be

successful and the comparability between the groups was good (Table 4).

Table 4. Baseline information given at the cluster and individual levels

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70

6.1.2. Changes in ergonomics

Participation rates in the workshops during the intervention were excellent, on average

73%. Altogether 402 ergonomics changes, evaluated by the researchers as being beneficial

with regard to load on the musculoskeletal system or occupational safety, were

implemented in the intervention group during the intervention phase. In the control group,

80 changes were implemented spontaneously within normal activity during the same

period. In the intervention group, over 100 of the intended changes were not completed

(Table 5). Both in the intervention and control group, the changes mostly concerned the

ergonomics of dishwashing, cooking and baking, and the distribution and serving of food.

In the intervention group, the largest proportion of changes was targeted at work

organization and methods (41%), whereas machines, equipment, and tools received the

most attention (52%) in the control group (Table 6).

Examples of implemented changes and of good practices in kitchen work have been

collected to the web pages of the FIOH and they are freely accessible

(www.ttl.fi/keittiovinkit). Pehkonen et al. (2009a) have described some of the

implemented changes in the context of the description of a video-based observation

method aimed to assess musculoskeletal load in kitchen work.

Table 5. Number of implemented changes during the intervention and the 12-month post-intervention follow-up in the intervention and control group, and uncompleted changes in theintervention group. The number of changes per kitchen is given in brackets

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71

Table 6. Distribution of implemented changes in the intervention and control group(402 vs. 80) subdivided according to work tasks and targets

*E.g. removal of doorsteps. †E.g. new package sizes. ‡E.g. removing objects causing risk of injury.

6.1.3. Effects on health outcomes

No systematic differences in any health outcome were observed between the intervention

and control group during the intervention or during the 12-month post-intervention follow-

up. Prevalence rates of musculoskeletal pain and sick leave during the past 3 months were

similar in the intervention and control groups (Figure 5). A few statistically significant

differences were found in the cross-sections, but mainly to a non-hypothesized direction.

Furthermore, no differences in MSP (� 3 pain sites) were found between the groups.

During the study period, the 3-month prevalence of MSP varied between 51% and 61% in

the intervention group, and between 47% and 59% in the control group (Figure 6).

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72

Figure 5. Musculoskeletal pain in seven anatomical sites and sick leave due to any pain duringthe past 3 months. Prevalence rates at baseline (BL), and every 3 months during theintervention (I) and the 12-month post-intervention (PI) follow-up. Comparison of theintervention and control group.*p < 0.05. †Some of the kitchens finished the intervention at 9 months (I9) and some at 12 (I12)months. Thus, the PIA, post-intervention assessment was a combination of these assessments.

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73

Figure 6. Multiple-site musculoskeletal pain (� 3 pain sites) during the past 3 months.Prevalence rates at baseline (BL), and every 3 months during the intervention (I) and the 12-month post-intervention (PI) follow-up. Comparison of the intervention and control group.*p < 0.05. †Some of the kitchens finished the intervention at 9 months (I9) and some at 12 (I12)months. Thus, the PIA, post-intervention assessment was a combination of these assessments.

The mean scores of trouble caused by pain during the past 3 months and local

musculoskeletal fatigue after a working day during the past 7 days displayed no significant

differences between the intervention and control group at any time point (Figure 7).

Figure 7. Mean values of trouble caused by any musculoskeletal pain during the past 3 monthsand local musculoskeletal fatigue after a working day during the past 7 days. Minimum, 25percentile, median, arithmetic mean (+), 75 percentile, and maximum. A comparison betweenthe intervention and control group.*Some of the kitchens finished the intervention at 9 months (I9) and some at 12 (I12) months. Thus,the PIA, post-intervention assessment was a combination of these assessments.

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74

Inclusion of the baseline covariates in the analyses did not change the results. The results

were similar among those who remained in the same kitchen throughout the study (cohort

analysis, n=307). Similarly, no differences between age groups (� 45 years vs. > 45 years)

in the effects of the intervention were observed. The effects of the intervention on health

outcomes were similar in the intervention and control groups in the cities where there were

organizational reforms and in the cities where no reforms took place (unpublished results).

6.1.4. Effects on perceived physical workload

Perceived physical workload showed no effect caused by the intervention. Overall mean

values for the intervention group were 3.7 [standard deviation (SD) 1.1] at baseline, 3.8

(1.0) at the end of the intervention, and 3.9 (1.2) at the 12-month post-intervention follow-

up. The respective figures for the control group were 3.7 (1.1), 3.8 (1.0), and 3.7 (1.2).

When subdivided according to work tasks, no significant differences between the groups

were observed (see the original publication I, Table 3).

6.2. Effects of the participatory ergonomics intervention on psychosocial

factors at work (II)

No favourable effects of the intervention on psychosocial factors at work were found.

Instead, a deterioration in several measures was observed. The adverse effects were

mainly due to a joint effect of the intervention and unconnected major organizational

reforms of foodservices in two of the participating cities.

Effects on psychosocial factors at work

Crude prevalence rates for each psychosocial factor at work at different time-points are

presented in Figure 8 and the effects of the intervention on psychosocial factors at work in

Table 7. At PIA, after adjustment for the baseline level of the outcome, workers in the

intervention group were more dissatisfied with their work (OR 3.0, 95% CI 1.1.-8.5), they

reported more mental stress (2.3, 1.2-4.7) and felt co-worker relationships to be poorer

(2.3, 1.0-5.2) compared to the workers in the control group. The effect on job

dissatisfaction persisted at PI12 (3.0, 1.2-7.8). In the fully adjusted model, poor co-worker

75

relationships and job dissatisfaction at PIA remained statistically significantly poorer in

the intervention group (see the original publication II, Table 3).

Figure 8. Crude prevalence rates of psychosocial factors at work according to organizationalreform (Org -, no organizational reform; Org +, organizational reform). The rates are based oncross-sectional data of an open sample. Comparison between the intervention and control groupat baseline (BL), at the end of the intervention (post-intervention assessment, PIA), and at the12-month post-intervention follow-up (PI12).*Some of the kitchens finished the intervention at 9 months and some at 12 months. Thus, the PIAwas a combination of these assessments.

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Table 7. Effects of the intervention on psychosocial factors at work. Odds ratios (OR) and 95%confidence intervals (CI) at the end of the intervention (post-intervention assessment, PIA), andat the 12-month post-intervention follow-up (PI12) for intervention group compared to controlgroup

*Adjusted for baseline level of the outcome.

Joint effects of the intervention and organizational reforms

No statistically significant independent effects of either the intervention or the

organizational reforms were detected at PIA or PI12. Instead, Figure 8 illustrates that there

was a joint effect between the intervention and the unconnected organizational reforms, in

relation to the psychosocial factors. At PIA, even after adjustment for all covariates,

mental stress was more common (OR above 3) among those with exposure to both the

intervention and organizational reforms, compared to those who were exposed to neither

(Table 8). Similarly, the mental strenuousness of work (OR over 2), job dissatisfaction

(almost 12), low job control (almost 3), and poor co-worker relationships (almost 6)

developed unfavourably in those workers subjected to double-exposure, i.e. both the

intervention and the organizational reforms. At PI12, this kind of joint effect was found for

mental strenuousness of work, hurry, low skill discretion, poor co-worker relationships,

and low supervisor support.

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Joint effects of the intervention and organizational reforms

No statistically significant independent effects of either the intervention or the

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was a joint effect between the intervention and the unconnected organizational reforms, in

relation to the psychosocial factors. At PIA, even after adjustment for all covariates,

mental stress was more common (OR above 3) among those with exposure to both the

intervention and organizational reforms, compared to those who were exposed to neither

(Table 8). Similarly, the mental strenuousness of work (OR over 2), job dissatisfaction

(almost 12), low job control (almost 3), and poor co-worker relationships (almost 6)

developed unfavourably in those workers subjected to double-exposure, i.e. both the

intervention and the organizational reforms. At PI12, this kind of joint effect was found for

mental strenuousness of work, hurry, low skill discretion, poor co-worker relationships,

and low supervisor support.

77

Table 8. Joint effects of the intervention and organizational reforms on psychosocial factors atwork. Those with no exposure to the intervention and no exposure to the organizational reformsas a reference group. Odds ratios (OR) and 95% confidence intervals (CI) based on cross-sectional analyses at the end of the intervention (PIA) and at the 12- month post-interventionfollow-up (PI12). Neither the intervention nor the organizational reforms had any statisticallysignificant independent effects on psychosocial factors at work at PIA or at PI12

*Adjusted for baseline level of the outcome. †Adjusted for baseline level of the outcome, age,musculoskeletal pain, and physical workload. ‡ Too few observations.

6.3. Occurrence of multiple-site musculoskeletal pain (III)

In studies III-IV, the study samples consisted of women only. At baseline, neck pain was

the most common (3-month prevalence 71%), followed by pain in the low back (50%),

forearms or hands (49%), shoulders (34%), ankles or feet (30%), knees (29%), and hips

(19%). The occurrence of pain at multiple-sites concurrently was more common than

single-site pain. Only 13% of the women reported no pain and 14% reported pain in only

one site. Instead, about 73% reported pain in at least two, 36% in four or more, and 10% in

six to seven sites. The symptoms occurred in 83 different combinations, in addition to

those with no pain and pain in one site only. The PRs for pain in a single site relative to

another varied from 1.3 to 5.8, e.g. neck pain was associated with pain in other sites with

PRs varying from 1.3 to 1.6, and ankle or foot pain with ratios between 1.9 and 2.4 (Table

9). When assessed in three larger anatomical areas, i.e. the axial skeleton (neck and low

back), upper limbs, and lower limbs, concurrent pain in all three areas was the most

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*Adjusted for baseline level of the outcome. †Adjusted for baseline level of the outcome, age,musculoskeletal pain, and physical workload. ‡ Too few observations.

6.3. Occurrence of multiple-site musculoskeletal pain (III)

In studies III-IV, the study samples consisted of women only. At baseline, neck pain was

the most common (3-month prevalence 71%), followed by pain in the low back (50%),

forearms or hands (49%), shoulders (34%), ankles or feet (30%), knees (29%), and hips

(19%). The occurrence of pain at multiple-sites concurrently was more common than

single-site pain. Only 13% of the women reported no pain and 14% reported pain in only

one site. Instead, about 73% reported pain in at least two, 36% in four or more, and 10% in

six to seven sites. The symptoms occurred in 83 different combinations, in addition to

those with no pain and pain in one site only. The PRs for pain in a single site relative to

another varied from 1.3 to 5.8, e.g. neck pain was associated with pain in other sites with

PRs varying from 1.3 to 1.6, and ankle or foot pain with ratios between 1.9 and 2.4 (Table

9). When assessed in three larger anatomical areas, i.e. the axial skeleton (neck and low

back), upper limbs, and lower limbs, concurrent pain in all three areas was the most

78

common (36%) combination and this increased statistically significantly (p< 0.005) with

age from 22% among the youngest group to 49% in the oldest group (Figure 9). The

longer the women had been employed in kitchen work, the higher was the prevalence of

pain in all three areas. There were no differences in the number of anatomical areas with

pain between kitchen aids, cooks and other occupations.

Table 9. Prevalence ratios (PR) for pain in a single anatomical site relative to another siteamong women in kitchen work (n=495). Cox regression analysis

*Treated as the dependent variable. † Treated as the independent variable. ‡Prevalence ratios arestatistically significant (p< 0.001), adjusted for 42 multiple tests.

Figure 9. Prevalence (%) of the number of painful anatomical areas (neck and low back, upperlimbs, lower limbs) during the past three months among women in kitchen work (n=495) by agegroup. Areas classified as no, one, two, and three.

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79

6.4. Reciprocal associations of multiple-site musculoskeletal pain with

psychosocial factors at work (IV)

6.4.1. Time-lagged associations

Since no overall positive effects of the PE intervention on musculoskeletal symptoms

(Figure 5) or on the occurrence of MSP (Figure 6) were found, the intervention and

control groups were pooled so that they could be analyzed in the two-year longitudinal

study.

All psychosocial factors at work, except low skill discretion and poor co-worker

relationships, predicted the occurrence of MSP (defined as pain at � 3 of seven sites) three

months later, odds ratios varying from 1.4 to 2.1 after adjustment for all covariates (Table

10a). MSP predicted low job control, low supervisor suppport, and mental stress (ORs 1.4-

2.0), respectively (Table 10b).

Table 10a. Psychosocial factors at work as determinants of multiple-site musculoskeletal pain(MSP, � 3 pain sites) among female kitchen workers (n=385). In a time-lagged generalizedestimating equation (GEE) model, psychosocial factors at work were assessed 3 months beforeMSP. Odds ratios (OR) and their 95% confidence intervals (CI)

*Adjusted for study arm, organizational reforms, and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload, and MSP.

� �� -�� '�3B@K�.A4D��2�� 86>�386=-:6@4� � �� 86C�3+6G-:6B4� �� &�� :68�386C-=6:4� ��-�� 86@�3+6>-:6*4� ��%� 86C�3868-86>4� �� 86*�3868-:6=4� �

*Adjusted for study arm, organizational reforms, and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload, and MSP.

80

Table 10b. Multiple-site musculoskeletal pain (MSP, � 3 pain sites) as a determinant ofpsychosocial factors at work among female kitchen workers (n=385). In a time-laggedgeneralized estimation equation (GEE) model, MSP was assessed 3 months before psychosocialfactors at work. Odds ratios and their 95% confidence intervals*

*Adjusted for study arm, organizational reforms and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload, and psychosocial factor atwork.


work

The 3-month prevalence of MSP varied from 50% to 61% during the two-year follow-up

period. There was no statistically significant overall trend in the prevalence. In the

trajectory analysis of MSP, the best fit was a four-group model including two trajectories

with the intercept (no change over time) and two with a linear shape (Figure 10). The

trajectory labelled as Low was composed of the workers whose prevalence of MSP was

constantly low (n=129, 33%), and the High trajectory of those with a constantly high

prevalence of MSP (n=146, 37%) over the two-year follow-up. The Descending trajectory

consisted of 66 workers (19%) and followed a declining pattern. The Ascending trajectory

was the smallest (n=44, 11%), and had a low initial prevalence of MSP that increased

considerably toward the end of the follow-up. The mean trajectory-group assignment

probabilities varied between 0.69-0.92, indicating that there was relatively little

classification uncertainty. The results of a sensitivity analysis using � 4 pain sites as the

cut-off point for MSP were similar. The four-group model with the similar shapes of the

trajectories had the best fit. The group sizes were 34% for Low, 28% for Descending, 13%

for Ascending, and 25% for the High trajectory, and the group assignment probabilities

varied from 0.77- 0.91.

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�� 86C�3868-:6+4��

86=�3+6B-:6+4�� :6+�386C-:6>4�� 86C�3+6B-:6=4�� +6>�3+6*-8684� :6+�386=-:6B4��

*Adjusted for study arm, organizational reforms and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload, and psychosocial factor atwork.


work

The 3-month prevalence of MSP varied from 50% to 61% during the two-year follow-up

period. There was no statistically significant overall trend in the prevalence. In the

trajectory analysis of MSP, the best fit was a four-group model including two trajectories

with the intercept (no change over time) and two with a linear shape (Figure 10). The

trajectory labelled as Low was composed of the workers whose prevalence of MSP was

constantly low (n=129, 33%), and the High trajectory of those with a constantly high

prevalence of MSP (n=146, 37%) over the two-year follow-up. The Descending trajectory

consisted of 66 workers (19%) and followed a declining pattern. The Ascending trajectory

was the smallest (n=44, 11%), and had a low initial prevalence of MSP that increased

considerably toward the end of the follow-up. The mean trajectory-group assignment

probabilities varied between 0.69-0.92, indicating that there was relatively little

classification uncertainty. The results of a sensitivity analysis using � 4 pain sites as the

cut-off point for MSP were similar. The four-group model with the similar shapes of the

trajectories had the best fit. The group sizes were 34% for Low, 28% for Descending, 13%

for Ascending, and 25% for the High trajectory, and the group assignment probabilities

varied from 0.77- 0.91.

81

Observed — Predicted ----

Figure 10. Multiple-site musculoskeletal pain trajectories (MSP, � 3 pain sites) among femalekitchen workes (n=385).1 = Low (low prevalence of MSP), 2 = Descending (decrease in prevalence of MSP),3 = Ascending (increase in prevalence of MSP), 4 = High (high prevalence of MSP).

Trajectories of psychosocial factors at work

The two-group model had the best fit for each of the psychosocial factors at work (Figure

11). Hurry had trajectories with the intercept shape with 23% of the workers belonging to

the High trajectory. All other psychosocial variables had one trajectory with the intercept

shape and the other with a linear ascending trend. The proportions of subjects belonging to

the ascending trajectories were 23% (low job control), 7% (low skill discretion), 21% (low

supervisor support), 10% (poor co-worker relationships), and 20% (mental stress). The

mean assignment probabilities for all psychosocial work factor trajectories were over 0.70.

�

Observed — Predicted ----

Figure 10. Multiple-site musculoskeletal pain trajectories (MSP, � 3 pain sites) among femalekitchen workes (n=385).1 = Low (low prevalence of MSP), 2 = Descending (decrease in prevalence of MSP),3 = Ascending (increase in prevalence of MSP), 4 = High (high prevalence of MSP).

Trajectories of psychosocial factors at work

The two-group model had the best fit for each of the psychosocial factors at work (Figure

11). Hurry had trajectories with the intercept shape with 23% of the workers belonging to

the High trajectory. All other psychosocial variables had one trajectory with the intercept

shape and the other with a linear ascending trend. The proportions of subjects belonging to

the ascending trajectories were 23% (low job control), 7% (low skill discretion), 21% (low

supervisor support), 10% (poor co-worker relationships), and 20% (mental stress). The

mean assignment probabilities for all psychosocial work factor trajectories were over 0.70.

82

Figure 11. Trajectories of psychosocial factors at work and mental stress among female kitchenworkers (n=385). Trajectories labelled as Low and Ascending (job control, skill discretion,supervisor support, co-worker relationships, and mental stress), or Low and High (hurry).

6.4.3. Associations of psychosocial factors at baseline with multiple-site

musculoskeletal pain trajectories

After adjustment for covariates, poor co-worker relationships (OR 3.9, 95% CI 1.2-12.4),

mental stress (3.1, 1.1-9.1) and hurry (2.1, 1.1-3.7) at baseline predicted belonging to the

High vs. the Low MSP trajectory (Table 11; Baseline). None of the psychosocial work

�

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83

factors at baseline predicted belonging to the Ascending vs. the Low or to the Descending

vs. the High MSP trajectory.

6.4.4. Association of multiple-site musculoskeletal pain at baseline with psychosocial

work factor trajectories

With the Low trajectory as the reference, MSP at baseline predicted belonging to the

Ascending trajectory of low job control (OR 2.2, 1.3-3.9) and of mental stress (3.2, 1.7-

6.0) (Table 12).

Table 11. Multiple-site musculoskeletal pain (MSP, � 3 pain sites) trajectories in relation topsychosocial factors at work and mental stress among female kitchen workers (n=385). Thepsychosocial factors have been assessed at baseline and as trajectories* (two groups, alwayscontrasting Ascending/High vs. No). Comparison between the MSP trajectories as follows:Ascending vs. Low, High vs. Low, and Descending vs. High†. Logistic regression analysis. Oddsratios (OR) and their 95% confidence intervals (CI)

*Development of psychosocial factors at work and mental stress over a two-year follow-up period.†Number of subjects in multiple-site pain trajectories: Ascending (n= 44), Low (n=129), High(n=146), Descending (n=66). ‡Adjusted for study arm, organizational reforms and the followingfactors at baseline: age, body mass index, smoking, physical exercise, perceived physicalworkload. §Adjusted for study arm and organizational reforms, and the following factors atbaseline: age, smoking, physical exercise, perceived physical workload. ¶ No observations in 'BLyes' category in the Ascending trajectory of mental stress.

.��(�� -�� 2��H�� &�6�� 2�� &�6��1�� H�� &�6�� 1�

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�� "��/�%��&�6�� +6B�3+68-B6G4� 8686�3+6:-@6C4� +6C�3+6+-=6@4�P�9��2��/�� &�6�� 86B�3+6C-B6@4� =68�386+-8+6=4� +68�3+6+-+6B4��

�� &�� "��/�%��&�6�� +6>�3+6:-:6>4� 86=�3+6*-=6+4� 86C�3+6*-=6=4�9��2��/�� &�6�� :6G�386+-*6B4� :6=�386:-C6G4� 868�3+6@-:6=4��

��-�� "��/�%��&�6�� 86:�3+6:-G6C4� =6B�386:-8:6C4� +6>�3+6=-:6:4�9��2��/�� &�6�� @6+�3868-:86*4� =6@�3868-886C4� 86+�3+6C-:6G4�

� � ��%� � � ��"��/�%��&�6�� 86:�3+6@-:6B4� :68�3868-=6G4� 86+�3+6@-:6+4�9��2��/�� &�6�� 868�3+6C-=6+4� 86G�3+6B-=6C4� +6B�3+6C-86B4��

�� "��/�%��&�6�� Q =68�3868-B684� +6B�3+6=-:6C4�9��2��/�� &�6�� @6@�386*-8B6+4� >6*�3=6=-::684� +6*�3+6=-86=4�

84

Table 12. Multiple-site musculoskeletal pain (MSP, � 3 pain sites) at baseline as determinant oftrajectories of psychosocial work factors and mental stress among female kitchen workers(n=385). Comparison between trajectories as follows: Ascending vs. Low* and High vs. Low †.Logistic regression analysis. Odds ratios (OR) and their 95% confidence intervals (CI) ‡

‡Adjusted for study arm, organizational reforms, and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload.

6.4.5. Psychosocial work factor trajectories in relation to multiple-site pain

trajectories

Trajectories of psychosocial factors at work as determinants of MSP trajectories are

presented in Table 11 (Trajectories). With the Low MSP trajectory as the reference,

adverse changes in all psychosocial factors at work, except in low skill discretion and

hurry, were associated with belonging to the Ascending MSP trajectory, with the odds

ratios varying from 2.7 to 5.5 after adjustment for covariates. Similarly, adverse changes

in all psychosocial factors, with the exception of hurry, were associated with belonging to

the High MSP trajectory (ORs 2.3 to 8.6). With the High MSP trajectory as the reference,

adverse changes in low job control and low skill discretion were inversely associated with

belonging to the Descending MSP trajectory (ORs 0.1-0.3).

These associations were in many cases stronger than the effects of the baseline levels of

the psychosocial factors on the MSP trajectories. Only poor co-worker relationships and

hurry at baseline had higher risk estimates compared with their trajectories in predicting

membership of the High vs. Low MSP trajectories. Hurry at baseline had also a slightly

higher risk estimate compared with its trajectory in predicting membership of the

Ascending vs. High MSP trajectory.

��2��D�

��3�

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��-�� D�

��%�4� �� D�

�� :6:�386=-=6B4� :6@�3+6B-G6:4� 86@�3+6B-:6G4� 86>�3+6>-C684 � 86@�3+6B-:6@4� =6:�386G-*6+4�

‡Adjusted for study arm, organizational reforms, and the following factors at baseline: age, bodymass index, smoking, physical exercise, perceived physical workload.

6.4.5. Psychosocial work factor trajectories in relation to multiple-site pain

trajectories

Trajectories of psychosocial factors at work as determinants of MSP trajectories are

presented in Table 11 (Trajectories). With the Low MSP trajectory as the reference,

adverse changes in all psychosocial factors at work, except in low skill discretion and

hurry, were associated with belonging to the Ascending MSP trajectory, with the odds

ratios varying from 2.7 to 5.5 after adjustment for covariates. Similarly, adverse changes

in all psychosocial factors, with the exception of hurry, were associated with belonging to

the High MSP trajectory (ORs 2.3 to 8.6). With the High MSP trajectory as the reference,

adverse changes in low job control and low skill discretion were inversely associated with

belonging to the Descending MSP trajectory (ORs 0.1-0.3).

These associations were in many cases stronger than the effects of the baseline levels of

the psychosocial factors on the MSP trajectories. Only poor co-worker relationships and

hurry at baseline had higher risk estimates compared with their trajectories in predicting

membership of the High vs. Low MSP trajectories. Hurry at baseline had also a slightly

higher risk estimate compared with its trajectory in predicting membership of the

Ascending vs. High MSP trajectory.

85

7. DISCUSSION

This study was intended to obtain evidence on the efficacy of PE in preventing MSDs, and

to examine its effects on psychosocial working conditions. An intensive PE intervention of

about one year's duration was conducted in municipal kitchens. The study was designed as

a CRT. The co-occurrence of musculoskeletal pain in various body sites, and the

association of MSP with psychosocial factors at work and mental stress were also

evaluated.

7.1. Main findings and comparison to earlier studies


disorders and psychosocial factors at work in the CRT

It was hypothesized that optimization of physical and mental workload would have a

preventive effect on the occurrence of MSDs and that active group work, and the direct

participation of the workers in problem-solving, planning and implementing the

ergonomic changes during the intervention would have a positive effect on the

psychosocial work environment in the intervention kitchens. However, the obtained results

did not support these hypotheses.

Although the intervention model proved feasible (Pehkonen et al. 2009c) and it was well

received by both the workers and management, no effect of the intervention was found on

musculoskeletal health. In some cross-sections, a few statistically significant differences in

pain prevalence were seen, but mainly in an unanticipated direction. In the intervention

group, the occurrence of pain seemed to be stable or even rising, and especially the

number of pain-related sick leaves increased compared to the control group. No

differences in trouble caused by pain or musculoskeletal fatigue were detected.

Perceived physical workload was not affected by the intervention. When the effects of the

intervention on psychosocial factors at work were analyzed, a deterioration was observed

in several of the workers' reports about psychosocial factors. At the end of the

86

intervention, the workers in the intervention group reported more mental stress, worse job

dissatisfaction and poorer co-worker relationships compared to the workers in the control

group. The effect on job dissatisfaction still persisted at the 12-month post-intervention

follow-up. An adverse joint effect of the intervention and organizational reforms was seen

for the majority of the eight measured psychosocial factors. Unfavourable effects on

psychosocial factors at work may partly explain why the intervention did not have the

expected impact on the occurrence of MSDs.

The variety in study designs, participants, outcome measures, and intervention programs

complicate the comparison of our results to earlier findings. Since the CRT by the Dutch

researchers (Driessen et al. 2008) is still underway and results are not yet available, the

study by Morken et al. (2002) appears to be the only one with a similar study design. Their

results were in line with the present findings. The study by Morken et al. (2002) aimed at

examining the effects of a PE intervention on MSDs, psychosocial factors, and coping and

included a large number of Norwegian aluminium industry workers. The intervention

groups included only operators, only supervisors, and both. The authors found no effect of

the intervention on MSDs, job demands, job control or social support, while coping skills

increased, particularly in the operator group. Organizational restructuring took place

during the intervention period. The authors collected information from the plants about

restructuring, but did not report whether they had considered its effects in their analyses.

They did not present sample size or power calculations or whether the clustering effect

(plants, workers) was taken into account. However, the study population represented the

whole aluminium industry sector and mostly consisted of men. The workers were from the

production line, where the work is physically demanding, and the occurrence of MSDs

among workers was high. The results of that study and the results of our study support and

complement each other.

Two individually randomized trials on physically lighter sedentary work among VDU

workers have been reported. Ketola et al. (2002) found a positive short-term effect of a PE

intervention on musculoskeletal discomfort at their 2- month follow-up. However, pain or

strain levels did not differ in the intervention groups compared to those in the control

group, and no long-term effects on discomfort, pain or strain were observed at the 10-

month follow-up. In the study of Bohr (2000), the intervention groups reported less upper

87

body pain/discomfort and work stress throughout the study period than the control group

but no effects on lower body pain/discomfort were found. There was a higher turnover

than expected particularly in the intervention groups. In a subsequent study, Bohr (2002)

found no evidence that participatory methods would have been more effective than

traditional methods in training in office ergonomics with regard to positioning work

equipment correctly or to maintaining good working postures.

In a non-randomized trial involving manufacturing workers, Laing et al. (2005, 2007) had

aims and results quite similar to those of the present study. They detected minor effects of

PE on physical workload and no changes in perceived effort or pain severity levels. In the

intervention group, communication dynamics regarding ergonomics were enhanced, but

no differences between the groups were observed in overall communication between

workers, co-workers and management.

This present study seems to be the first large CRT that has evaluated the efficacy of a PE

intervention in reducing psychosocial load at work. Recently, Tsutsumi et al. (2009)

examined the effect of a participatory workplace improvement intervention on mental

health and job performance. The study was conducted in a company producing electrical

devices. They randomized 11 assembly lines to an intervention (47 workers) and a control

group (50 workers). Multilevel modelling was used to take into account that individuals

were nested in units of assembly lines. Mental health and job performance improved in the

intervention group compared to the control group. However, the overall effect was minor,

the final sample sizes for the analyses were small, and after imputation of missing values,

no significant effect was found. In addition, a non-randomized controlled trial by

Kobayashi et al. (2008) was conducted in a manufacturing company. Nine of 45

departments participated in the intervention, and the remaining 36 departments served as

the control group. Positive effects on mental health among women were found, but not

among men.

One basic aim of the participatory approach is that the workers learn new skills during the

process (Haines and Wilson 1998). Learning and internalizing of the principles of

ergonomics gives the workers the capability to independently and continuously develop

ergonomics in their daily work. In this present study, most of the changes in the

88

intervention group were targeted at work organization and methods (41%), whereas in the

control group machines, equipment and tools received most attention (52%). After the end

of the intervention, about 100 ergonomic changes had been implemented in the

intervention group during the 12-month post-intervention follow-up period, indicating that

the aim of learning was achieved.

Joint effects of the intervention and unconnected organizational reforms on

psychosocial factors at work

The adverse overall effects of the PE intervention on psychosocial factors were

accentuated in the kitchens with concomitant unconnected organizational foodservice

reforms. No independent effects of either the intervention or the organizational reforms

were detected. In some previous studies, interventions aimed at the redesign of work have

had an adverse effect on psychosocial working conditions. A reorganisation of work at an

automobile assembly plant resulted in a considerable decrease in the perception of

opportunities to influence the work and in the degree of stimulation at work (Fredriksson

et al. 2001). After the intervention, the prevalence of MSDs increased in the intervention

group, but not in the control group from the same plant. High perceived workload and

reduced occupational pride were associated with the increase in MSDs. Christmansson et

al. (1999) observed that organizational redesign of manual repetitive assembly jobs mostly

impaired the psychosocial work environment and increased the physical stress and risk of

MSDs.

Unexpected organizational reforms have been shown to interfere negatively with

interventions (Lagerström et al. 1998; Demure et al. 2000) and it is not uncommon that

long-lasting intervention studies may be confronted by unforeseen changes beyond the

control of the researchers (Cole et al. 2003; Silverstein and Clark 2004; Heaney and

Fujishiro 2006). In this study, the centralizing of food preparation to certain kitchens

during the organizational reforms increased the number of kitchens where food was only

distributed to the clients. As a result, work tasks probably became more monotonous in the

latter kitchens and diminished workers' possibilities to use their skills. The threat of

outsourcing the functions or restructuring the foodservice as a public utility may have

increased the employees' fear of redundancy causing uncertainty, extra tension and

competition between the workers.

89

A participatory process can have negative effects on the psychosocial aspects at work if

the process entails extra work (St-Vincent et al. 2006). In the present study, the

participation in the intervention simultaneously with the implementation of the

organizational reform may have been overly stressful to the workers. Participation in the

workshops was more active in the cities with than in those without reforms, possibly

increasing the overload of the workers in the midst of elevated work demands.

Perceived physical workload

No effect was found that the intervention would have altered perceived physical workload.

The number of portions prepared per worker has been shown to be associated with MSDs

(Shibata et al. 1991; Ono et al. 1997; Nagasu et al. 2007). According to the research

diaries, in about one third of both the intervention and control kitchens, the number of

portions increased during the study. A decrease in the number of personnel was recorded

in four intervention and eleven control kitchens. This may have led to a higher

intensification of work being done in the control kitchens.

Kitchen work is demanding, both physically and mentally. The employees work under

pressure of time and perform various parallel tasks, many of which include exposure to a

combination of risk factors of MSDs. For example, in long-lasting dishwashing, in

receiving and storing of raw material, and cooking, the individual makes frequent bending

and twisting of the trunk, lifting, repetitive movements of the hand, non-neutral wrist and

shoulder postures, and there is need for forceful hand movements. The kitchen workers

spend the working day almost exclusively walking or standing. Messing and Kilbom

(2001) conducted a small workplace field study to assess the consequences of prolonged

walking and standing among kitchen workers. They found that prolonged standing and

short-distance slow walking caused a decrease in the plantar pain-pressure threshold over

the workday. The majority of the workers had experienced foot pain during the previous 3

months. In the light of these results, it might be that standing or walking could be

associated with lower limb pain. There is evidence that exposure to both dynamic and

static repetitive motions, forceful exertion, and non-neutral body postures may cause

MSDs in one or more anatomical sites (Punnett and Wegman 2004). The high occurrence

of MSP found in this study could be connected with the pattern of loading in kitchen

work. Workload may be rather uniformly distributed on the musculoskeletal system.

90

Reducing physical workload on musculoskeletal system is not straightforward. A

reduction of biomechanical exposure on some body part may lead to an increased

exposure on another and thus only transfer the site of the problem. It is difficult to

quantify the exact levels of biomechanical exposure that are harmful to the

musculoskeletal system. Thus, at best, one only knows that the level of exposure needs to

be reduced, but not to what degree. Primary preventive interventions to reduce

biomechanical exposure may encounter difficulties in demonstrating that a reduction in

biomechanical exposure has resulted in a lower occurrence of MSDs. It has been proposed

that a reduction of at least 14% in biomechanical exposure is required to achieve any

detectable change in MSDs (Lötters and Burdof 2002; Burdorf 2010).

The results on physical risk factors based on objective expert assessment showed for some

work tasks a reduction of the level of exposure (unpublished results). A subgroup analysis

where the intervention and control groups were pooled showed that both the observed

reduction in lifting and the perceived physical workload reduction in receiving and storing

of raw material were associated with a lower risk of further shoulder symptoms during the

12-month follow-up (Pehkonen et al. 2009b).Yet, no overall effect of the intervention on

perceived physical workload was detected. One explanation for this apparent discrepancy

might be that the intervention did not produce a strong enough change on physical

workload in the intervention group compared to the annually spontaneously implemented

changes in the control group. It seems that the changes were not strong enough to

influence the overall physical workload or the health outcomes. In some kitchens,

acquisition of expensive new equipment and extensive structural changes would have been

needed. Since no extra funding was available, most of the changes were low cost

solutions.

7.1.2. The occurrence of multiple-site musculoskeletal pain

Since the number of men was low (4% in study III, 3% in study IV), the analyses

concerning the occurrence of MSP and associations of MSP with psychosocial factors at

work were conducted only in women. The cross-sectional study (III) described the overall

prevalence of pain and specifically that at multiple sites concurrently at baseline, before

the intervention started. Neck pain was the most common with seven of ten workers

91

reporting it, while every second worker reported forearm or hand pain and LBP. These

estimates are higher than usually found in the normal female population of a comparable

age range (Picavet and Schouten 2003; Bingefors and Isacson 2004; Kaila-Kangas 2007)

and among the highest published in occupational samples (Blatter and Bongers 1999;

National Research Council and Institute of Medicine 2001; Riihimäki 2005a). The one-

month prevalence of LBP among Japanese female cooks working in school lunch services

was recently reported to be 75% (Nagasu et al. 2007), that is even higher compared to the

3-month prevalence (50%) desribed here.

The finding of a high occurrence of MSP is in line with previous results among

occupational samples and in the general population. The estimates for MSP among kitchen

workers were even higher than those that have been presented in the general population or

in occupational samples. About 73% of female kitchen workers reported pain in at least

two sites. The respective figures among a representative sample of Finnish adults was 33%

(Miranda et al. 2010), in the Dutch population 50%, and in Dutch women 39% (Picavet

and Schouten 2003). Recently, Solidaki et al. (2010) evaluated MSP among Greek nurses,

office workers and postal clerks. The study sample (n= 564) comprised predominantly of

women, and 66% reported pain in two or more sites. In men doing manual lifting work,

63% had pain in at least two sites (Yeung et al. 2002). However, all comparisons are

hampered by the sensitivity of pain prevalence estimates to differences in the way that the

question was worded and different reference periods.

The seven pain locations did not cluster in any simple manner in our study material. Two

thirds of the theoretically possible (27=128) combinations were empirically detected.

When pain in three larger anatomical areas (neck and low back, upper limbs, lower limbs)

was studied, every third woman (36%) reported pain in all three anatomical areas and

every second of those aged 51-63 years, i.e. the co-occurrence of pain was age-related. It

is possible that degenerative changes in the musculoskeletal system could contribute to

phenomenon. According to the ACR criteria, classification of CWP includes pain in the

upper and lower extremities (both sides of the body) and axial pain that must have been

present for at least three months (Wolfe et al. 1990). Such a definition could not be applied

here, as no information was availabe on pain persistence or on pain in the left and right

lower limb separately. The observed amount of overlap in pain areas in this study is

92

clearly higher than the prevalence of CWP found in previous surveys. It has been

estimated that approximately 10% of the general population report CWP and almost

unanimously all studies have found higher rates among women compared with men, but

the mechanism responsible for the skewed gender ratio remains unknown (Gran 2003).

In Finland, as well as across all other EU member states the workforce will age rapidly

over the next 40 years, bringing with it the risk of increasing MSD prevalence. In other

words, the impact of MSDs on work disability can be anticipated to intensify rather than

diminish. Two thirds of the European workforce with MSDs reported that pain was

responsible for a significant reduction in their quality of life, and 49% were limited

because of pain in the kind of work they were able to perform (Bevan et al. 2009). MSP

poses extra challenges, because it seems to be more disabling than single-site pain both in

population-based surveys and in occupational samples.

7.1.3. Association of multiple-site musculoskeletal pain with psychosocial factors at

work and mental stress over time

Many reports recommend that consideration of pain at several sites simultaneously is

preferable to the assessment of one pain location in isolation. Nonetheless, most studies

have traditionally examined prognostic factors of single-site pain (Mallen et al. 2007) and

the risk factors of the occurrence of MSP are not well known. The need to provide

information on why pain tends to occur at multiple sites and to examine the occurrence of

MSP over time has recently been emphasized (Croft et al. 2007). Many of the

psychosocial factors at work have been found to be associated with musculoskeletal pain,

mostly in cross-sectional studies. However, in cross-sectional studies, it is not possible to

estimate the timing of determinant and outcome, as the both are assessed at the same time.

The need for conducting longitudinal studies in this area is evident (Macfarlane et al.

2009).

Since no systematic differences between the intervention and control group in our CRT

were found in MSDs, MSP or perceived physical workload, the groups were pooled for

analysis as a two-year longitudinal study (IV). There were two hypotheses, with reversed

directionality. First, the intention was to determine whether psychosocial factors at work

93

and mental stress predicted the development of MSP over time, and second, whether MSP

could predict the occurrence of psychosocial factors at work and mental stress.The

reciprocal analyses were based on the finding of Leino and Magni (1993) who examined

metal industry workers. They found that symptoms related to mental stress predicted an

increase in a sum score of musculoskeletal pain at several sites, and respectively, the pain

sum score predicted an increase in stress symptoms.

In etiological longitudinal studies, usually the relation between an exposure measured at

baseline and the occurrence or change of the outcome during the follow-up period is

examined. In this work, it was possible to make use of two different types of longitudinal

analyses in assessing relationships between the measures. One of these examined the

situation at three-month intervals (the GEE) and the other described them using the total

two-year follow-up period (trajectories). The use of trajectories also enabled the

examination of changes in psychosocial factors at work in relation to changes in MSP over

time.

The 3-month prevalence of MSP (defined as pain at � 3 of seven sites) varied between 50-

61% during the two-year follow-up. According to this definition, the workers in the

category of no MSP could still have pain at 1 to 2 sites. A quarter of the workers reported

pain in at least two sites at every nine assessed time points. This is noteworthy because

having pain at one site is shown to increase the risk of developing pain at other sites and

the risk increases with the number of initial painful sites (Croft et al. 2007; Kamaleri et al.

2009). The average number of pain sites appears to be set already by age 20 and little

variation seems to occur thereafter (Croft 2009; Kamaleri et al. 2009). However, it was

found that some variation, even a decrease, in the occurrence of MSP in working age is

possible. Trajectory analysis identified four trajectories of MSP prevalence and it was

observed that 19% of the workers belonged to the trajectory with a descending pattern in

the prevalence of MSP.

The three analyses support both of the study hypotheses. First, in time-lagged analysis,

psychosocial factors at work predicted MSP reported three months later, and vice versa,

MSP predicted adverse psychosocial factors at work after adjustment for covariates. The

risk estimates were comparable in both directions with the exception of hurry at work,

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which predicted MSP but was not predicted by MSP. Secondly, poor co-worker

relationships, mental stress and hurry at baseline predicted belonging to the High MSP

trajectory. In addition, MSP at baseline predicted belonging to the trajectories of

Ascending low job control and mental stress. Finally, the adverse development in most

psychosocial factors was associated with belonging to the High and Ascending MSP

trajectories. This reciprocal linkage complicates conclusions of the causal nature of the

relationships between these factors. Two possibilities seem to exist: this finding either

reflects two processes that are mutually and serially dependent in time or there is/are some

common underlying factor(s).

With regards to the relationships between mental stress and MSP, these current findings

basically replicate those reported by Leino and Magni (1993) with a somewhat different

measure of MSP and in a different occupational setting. As far as I am aware, no

systematic reciprocal analyses with pain symptoms and psychosocial factors at work have

been carried out before. This present study seems to be the first to examine developmental

patterns of MSP and of psychosocial factors at work. Overall, few longitudinal studies

exist in this subject area among general population or occupational samples.

Differences in study designs, samples, and measures of outcomes and determinants,

complicate the comparison of these results with those of previous studies. However, our

findings are in accordance with some earlier reports in line with our first hypothesis. Leino

and Hänninen (1995) reported that after adjustment for physical workload, poor social

relationships at work and poor job control predicted an increase of pain and

musculoskeletal clinical findings in the neck and upper limbs, low back, and lower limbs

in a 10-year follow-up. Dissatisfaction with support from colleagues or supervisors was

found to increase the risk of future episodes of forearm pain that commonly co-occurred

with other regional pain (Macfarlane et al. 2000). In this study, poor co-worker

relationships at baseline predicted belonging to the group with a constantly high

prevalence of MSP. The time-lagged analysis showed that low supervisor support and low

job control increased the risk for MSP about two-fold. It may be that in small work

communities where work is done in close co-operation, there is an emphasis on the

importance of good social relationships for well-being.

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In these GEE-models, mental stress and hurry predicted MSP. It was also found that

mental stress and hurry at baseline predicted reporting chronic MSP, a finding in support

of earlier results. Nahit et al. (2001) conducted a cross-sectional study among newly

employed workers (n= 1081, median age 23 year) and observed that those who perceived

their work as stressful and hectic for most of the time had an increased risk of pain at

multiple sites. Later, based on the same study sample, they reported that high levels of

individual psychological distress and adverse work-related psychosocial factors predicted

the onset of musculoskeletal pain at a one-year follow-up with similar effects across

anatomical sites (Nahit et al. 2003). The median age (47 years) in the presnt sample was

higher. It could be that regardless of age, mental stress and hurry might increase the risk of

MSP.

In cross-sectional studies, women, smokers, overweight subjects and those with low

physical activity have reported a greater number of pain sites (Walker-Bone et al. 2004;

Kamaleri et al. 2008a). In the present female sample, smoking had no effect on the

development of MSP. Risk estimates for overweight were increased, but not statistically

significantly. Instead, perceived physical workload and age predicted an increase and a

constantly high prevalence of MSP (unpublished results).

Mental stress and other psychosocial factors may be linked to MSDs with many pathways.

Psychosocial factors may have a direct influence on the loading on the spine through

changes in postures, movements, and exerted forces. Psychosocial factors may trigger

chemical and physiological responses. Increased hormonal excretion or muscle tension

may influence pain perception and in the long-term lead to MSDs. Psychosocial factors

can influence awareness, and alter the ability to cope with the pain and illness and possibly

increase the likelihood of reporting of symptoms (Bongers et al. 1993; Sauter and

Swanson 1996; Davis and Heaney 2000; Hoogendoorn et al. 2000; Bongers et al. 2002).

This study raises the question about the mechanism behind the finding that the occurrence

and development of MSP over time predicts the occurrence and development of adverse

psychosocial working conditions. It is perhaps noteworthy that both measures were based

on subjective perceptions. There might be common underlying factor(s), and these will

require further study.

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7.2. Methodological aspects

7.2.1. Validity of the CRT

The CRT (study I) is included in three systematic reviews focusing on the effectiveness of

workplace interventions for LBP and neck pain, one by Dutch researchers (Driessen et al.

2010) and the other two by a Nordic research group in the Cochrane collaboration (Aas et

al. 2009a; Aas et al. 2009b). In these reviews, the risk of bias is assessed by using the 12-

item Cochrane Back Review Group criteria list. The quality of the present study was

evaluated to be high (scores 9/12, Driessen et al. 2010). The criteria of blinding were not

fulfilled. In our view it is not possible to conduct a PE intervention in a blinded manner.

However, the baseline data on all outcomes and measures were collected before

randomization, so that the workers participating in the study or the researchers ('care

providers') were not conscious of the study arm to which the workers would be

allocated. After randomization, both the workers and researchers were aware of the

allocation. The researchers were blinded with respect to the questionnaire data during the

data collection, and data analysis was started only after all the follow-up data had been

collected.

As an additional requirement is that those assessing outcomes ('outcome assessors') should

be blinded about the study arm. The outcomes were based on self-reports collected by

questionnaires. It is conceivable that the workers in the intervention group may have been

sensitized to perceive and report their MSDs and psychosocial factors at work. The

magnitude of this possible bias is difficult to assess.

Randomization was based on an assignment algorithm generated by a computer. An

individual otherwise unconnected with the implementation of the intervention was

responsible for the randomization. Randomization was successful and good comparability

between the groups persisted throughout the study. This was true even in spite of the

organizational reforms carried out in two cities, because the study design guaranteed a

parallel proceeding in time of both study arms within each series of kitchens. Stratification

by area and type of kitchen ensured balanced clusters with respect to baseline

characteristics.

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Data were analysed according to the intention-to-treat principle. Three kitchens dropped

out after the randomization. No information after the baseline questionnaire on these

kitchens was available, and it was not possible to make any further analyses on them. This

situation is remotely analogous to the case where the patient dies before starting the

medication/treatment. It is not generally considered that a situation such as that violates

the intention-to-treat principle. All three dropout kitchens were randomized to the

intervention group. In one kitchen, the study was considered too cumbersome. Otherwise

the reasons were coincidental. The amount of dropouts was minor in relation to the total

number of kitchens. At least 70% of the workers remained employed in the same kitchen

throughout the study. Despite the staff turnover, the groups remained similar through the

intervention phase with regard to assessed potential confounders. All these observations

indicate that selection or attrition bias did not threaten the validity of the study.

There was a relatively large sample size and sufficient statistical power. The clustered

nature of the data was taken into account in the power calculation and in the analyses of

the results. Because this intervention was targeted at the kitchen (community) level, we

used repeated cross-sectional analyses of the open population. This approach has been

recommended as being more appropriate than cohort analyses for measuring the

effectiveness of interventions in the community. The disadvantages of this approach have

also been pointed out. The analyses possibly include workers who receive limited

exposure to the intervention or that elements of the intervention diffuse to other

communities (Ukoumunne and Thompson 2001; Atienza and King 2002). However, the

present results in the open population were similar to those in the cohort analysis among

subjects who remained in the same kitchen throughout the study.

There were very high response rates, participation in the workshops was good, and no

dropouts occurred during the intervention, indicating good compliance. If the workers

changed kitchen, they were asked not to talk about the study process. Only two workers

were transferred from an intervention kitchen to a control kitchen during the intervention.

Thus, one can state that contamination was probably minor. Co-interventions/external

changes were similar in the intervention and control groups. The most prominent external

change was the re-organization of food service in two of the participating cities during the

study. The intervention and control group were in the same phase of the changes

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throughout the study. On average, series of four intervention and four control kitchens

entered sequentially in calendar time. Quality control based on regular meetings was

applied to ensure that there was similarity in the working methods between the researcher

teams working in the different cities. In addition, a project coordinator participated in the

workshops and observed the working of the researchers and provided them with feedback.

The inclusion of a 12-month post-intervention follow-up is also among the strengths of

this study. However, it may be that the intervention was not intensive enough. Due to

financial and time constraints, the follow-up period was limited to one year. An even

longer follow-up would have been needed to note the impacts on the musculoskeletal

system and to examine the persistence of the adverse changes in psychosocial factors at

work. Given the episodic nature of MSDs, the 3-month prevalence measures may not have

been optimal to capture a change in the frequency of bouts of MSDs. The measures of

local musculoskeletal fatigue during the past seven days were more sensitive. However, no

effect was detected using either fatigue measure.

A source of bias might arise from the fact that the workers had an active role in

implementing the ergonomic changes and the outcome assessments were based on their

subjective reports. It is conceivable that their involvement in an intervention program

increased the workers’ awareness of both ergonomics as well as musculoskeletal

problems. Being involved in the intervention may have encouraged the workers to develop

unrealistic expectations for the intervention to improve ergonomics and psychosocial work

environment. This might have been reflected via the increase in the adverse changes in

psychosocial factors at work.

The personal visits of a researcher to each of the kitchens encourage the workers to

complete the questionnaire probably was one of the reasons for the excellent response

rates. The researcher also documented changes in the control kitchens based on short

interviews. The visits can be interpreted as a kind of intervention for the control kitchens,

but their potential contribution to the results remains speculative. The visits may have

increased awareness of MSDs also in the control kitchens, which could have reduced

information bias regarding musculoskeletal outcomes. Documentation of the changes

during the visits may have activated the workers in the control kitchens to undertake more

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changes, which could have diluted the overall effect. Still, the difference in the number of

changes made in the intervention kitchens and those that occurred spontaneously in the

control kitchens (402 vs. 80) is considerable. On the other hand, it has been recommended

that the groups should be dealt with as similarly as possible, except for the intervention

itself, to avoid the 'Hawthorne effect' (Westgaard and Winkel 1997; Shannon et al. 1999).

Intervention process

The intervention process has been carefully evaluated and reported (Pehkonen et al.

2009c). The process evaluation was based on research diaries, questionnaires, and focus

group interviews. The intervention model and the participatory approach as such were

found to have been successful, well accepted and perceived as motivating. The workers’

ergonomics knowledge level increased and, in the workers’ own words, they developed an

'eye for ergonomics' with repect to their own work and that of others. Interestingly, most

of the workers felt that the intervention had had a positive effect on physical load and

musculoskeletal health, although the results did not support the hypothesis.

The workers conveyed that the feeling of togetherness within their own kitchen had

improved and that the intervention had facilitated discussion among and asking for help

from co-workers. The rotation of the workshops in different kitchens was felt to be

beneficial in enabling learning from each other's good practices. On the other hand, the

workers were dissatisfied with the support from the management and collaboration

between the kitchens, especially in one of the cities which was in the process of

implementing organizational reforms. The more satisfied the kitchens were with the

support from management, the better were the impacts of the intervention as evaluated by

the workers. The workers expected also more support from the researchers and technical

staff. A total of 113 planned changes were not completed. The most common reasons for

non-completion of changes were lack of motivation or time. The major observed obstacles

in improving kitchen ergonomics were passivity and resistance to change (Riihimäki

2005b).

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7.2.2. Clinical importance and generalization of the CRT findings

About 60% of all eligible kitchens took part in the study. Of the 80 non-participating

kitchens, some kitchens collectively refused to participate. In some cases, the decision of

refusal was administrative (e.g. made by the manager of the nursery or the headmaster of

the school), and in some kitchens at least one-third of the workers individually refused to

take part. In other cases, participation was withdrawn since there was going to be a major

reconstruction in the kitchen. The non-participating kitchens did not differ from their

participating counterparts in terms of size or location. However, no additional information

on the workers employed in the non-participating kitchens was available. Foe example, it

is possible, that physical or mental overstrain or poor social relationships at work could

have influenced the willingness to participate in a time-consuming intervention study. It

seems less likely that the workers in the non-participating kitchens would have had

different levels of pain or higher exposure to physical and/or mental workload compared

to those in the participating kitchens.

The results indicate that it is difficult to influence the heavy overall mental and physical

workload of kitchen workers without making structural changes in the kitchens and

redesigning whole work processes. There was no possibility to affect the basic design of

the kitchens or the amount of work by intervention. The ergonomic changes of the present

study mostly concerned micro-ergonomics. It may be that to obtain favourable effects on

the musculoskeletal health of the workers, a more comprehensive redesign of work

organization and processes is needed, taking more account of workers' physical and

mental resources (macro-ergonomics). The development of work should be a continuous

activity and it requires smooth collaboration between workers, management, planners,

architects, and technical staff.

The results can be generalized to other municipal kitchen workers. Although our study has

been evaluated to have a low risk of bias (Driessen et al. 2010), care must be taken in

generalizing the results beyond the target population. The amount of high quality RCTs or

non-randomized trials is insufficient to drawing conclusions of the utility of the PE

approach aimed at preventing MSDs. There is a need for further trials to elucidate this

issue.

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7.2.3. Methodological aspects in studies of multiple-site musculoskeletal pain

In the cross-sectional study (III), both 3- and 12- month reference periods were used to

assess the prevalence of musculoskeletal pain. Different reference periods did not

materially affect the prevalence of pain. This is in accordance with previous Nordic

studies (Ørhede 1994). The 3-month reference period was considered more reliable due to

the shorter required span of memory, and was used in further analyses as also

recommended by Ørhede et al. (1994). The 3- month reference period was used also in all

other studies (I, II, IV). Illustrations showing the area of interest were used in the

questionnaire. A verbal description might leave too large a share for individual opinion on

what represents the neck, shoulder, forearm/hand, and low back. This probably enhanced

the reliability of reporting. It could be argued that a similar approach might have been

preferable for hip pain as well. On the other hand, van den Hoven et al. (2009) recently

assessed the agreement between showing the participants a manikin to locate the pain sites

and a self-administered questionnaire on musculoskeletal pain. They concluded that the

manikin gave similar findings on the prevalence of pain as written questions and they

stated it could be a good alternative for written questions only. However, the manikin

revealed higher pain prevalence rates. It could be that the use of a manikin to illustrate the

area of body site in addition to a written question may have lowered the threshold for

reporting pain in this study. One limitation in these studies was the lack of intensity and

frequency measures of pain.

The use of a trajectory analysis was a novel approach in analyzing MSP. In the field of

psychology, this method is commonly used, but it has not often been applied in the area of

musculoskeletal research. Trajectory analysis is developed for analyzing longitudinal data

and identifying different groups of individuals within a population who tend to have a

similar profile over time (trajectories). All available data points during a given period are

used. Even though the prevalence of musculoskeletal symptoms may be similar at

different time points in longitudinal studies, there is often high variation in pain reporting

over time at the individual level (Takala et al. 1992). Trajectory analysis was able to make

the maximum use of the data, examining the development of MSP as well as that of

psychosocial factors at work over time.

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In conducting trajectory analysis, it has been recommended that measurements should be

available in at least half of the assessed time points if one wishes to reliably assess group

membership probabilities, and in at least three time points to detect trajectories of

quadratic shape (Kokko 2004). Thus, only subjects with observed values of MSP in at

least four time points of the nine possible were included. The sensitivity analysis, where

we dropped out 20 individuals with mean posterior assignment probabilities lower than

0.60, did not change the basic result of the number or shape of the MSP trajectories.

According to the mean posterior assignment probabilities, 69-92% of the subjects were

correctly assigned to the trajectories. In addition, the assignment probabilities for all

psychosocial work factor trajectories were over 0.70, as recommended (Nagin 2005).

The cut-off point for MSP is not well established. By trajectory analysis, the development

of MSP was first analyzed with MSP as a continuous variable. Forty-two per cent of the

workers were assigned to the trajectory comprised of those reporting pain in at least three

sites of seven. We then dichotomized MSP and used � 3 pain sites as a cut-off point. The

results of the sensitivity analysis by using � 4 pain sites as the cut-off point did not change

the basic result regarding the number and shape of the trajectories.

Although the sample was large enough to permit trajectory analysis (Kokko 2004), it was

relatively small for the assessment of risk, increasing imprecision of the estimates. Among

the limitations of this study could be the assessment of psychosocial factors at work by

single items. A single-item measure of mental stress has proved a valid measure, however

(Elo et al. 2003). All of the measured psychosocial factors at work have been identified as

risk factors for MSDs. The present study sample consisted of women in a single

occupational group. Hence, the generalizability of the results may be limited and can with

confidence be extended to other occupations where there are small work communities, a

high physical workload, and tight time constraints at work. Similar analyses among men

would be interesting and worthy of further study.

7.2.4. Self-reported outcome measures

All of the outcome measures were based on self-reports collected by questionnaires. Self-

reported symptoms collected by questionnaires have largely been basic data source in

epidemiologic research regarding MSDs. Questionnaires offer a quick and inexpensive

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data collection on an individual basis from large samples. The use of self-reported pain

has been proposed to be the most valuable approach to measure outcome in population-

based surveys (Schierhout and Myers 1996). The International Association for the Study

of Pain defines pain as 'an unpleasent sensory and emotional experience associated with

actual or potential tissue damage or described in terms of such damage' (Merskey and

Bogduk 1994). Pain may also occur in the absence of tissue damage or any likely

pathophysiologic cause. Pain is always a subjective sensation. Yet, pain research has

recently provided new interesting findings based on brain imaging studies that have

identified within-subject relationships between regional pain activity and subjective pain

reports. However, the subjective report will probably remain the single most reliable index

for the magnitude of pain (Coghill et al. 2003).

The majority of research reports on the psychosocial work environment have been based

on self-reported assessments (Theorell and Hasselhorn 2005). The questions used in this

study were from a validated Occupational Stress Questionnaire (Elo et al. 1992; Elo et al.

1994). The problem of self-reported data is substantial in cross-sectional studies when

both psychosocial environment and health are described by self-reports and when both are

assessed concurrently. It is not clear to what extent self-reports of psychosocial work

factors reflect individual characteristics and to what extent they reflect true environmental

conditions. It has been argued that subjectivity bias may explain most of the observed

associations between psychosocial working conditions and health. Some people may have

a tendency to overreport problems in the environment and also in their own health

(negative affectivity). Similarly, some may underreport problems in both psychosocial

environment and health (denial) (Theorell and Hasselhorn 2005). Nahit et al. (2001)

discussed that one way to objectively measure an individual's psychosocial working

conditions could be to ask a co-worker or manager to do the assessment. Work unit

aggregated scores have been used to assess job strain among Finnish public sector

employees (Laine et al. 2009). Overcrowding in hospital wards has recently been used as a

proxy for mental strain of hospital staff (Virtanen et al. 2008). However, one may argue

that in some respects, the worker's own assessment is the most valid estimate, particularly

if the psychosocial work environment as perceived by the worker is being enquired. In the

present situation, it is possible that the awareness of both musculoskeletal pain and

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psychosocial factors increased during the research period and lead to a more critical

evaluation by the workers.

A self-administered questionnaire is still the most widely used method also for assessing

physical workload (Barrero et al. 2009; Burdorf 2010). The reliability and validity of

physical workload assessments based on self-reports have been often criticized (Viikari-

Juntura et al. 1996; Buchholz et al. 2008; Burdorf 2010). In some previous studies, self-

reported physical workload has been shown to be a powerful predictor of MSDs and

physical functioning (Miranda et al. 2001; Leino-Arjas et al. 2004). Questionnaires are

also useful in identifying relative differences in exposure among occupational groups and

rank the groups according to their overall level of physical workload (Viikari-Juntura et al.

1996; Burdorf 2010). Direct measurements are costly and their laboriousness makes them

less feasible for use in epidemiologic studies. In a systematic review Takala et al. (2010)

recently evaluated observational methods assessing biomechanical exposures at work.

They found that though many methods exist, none of those evaluated appeared to be

superior to the others. Only some of the methods have been systematically tested for

validity, repeatability and feasibility.

7.3. Study findings in relation to the theoretical framework of the study

Karsh (2006) and Huang et al. (2002) have reviewed the theories and models of work-

related MSDs causation. These theories share many similarities. All of them emphasize

that psychological or physical exposures lead to responses that are moderated by

individual factors. Most of the models propose a feedback mechanism or cascading

effects. One common feature to all the theories is that many important aspects are not

defined, e.g. what is the magnitude and duration of an exposure that leads to certain

responses, or the length of the latency period between exposure and response. Some

theories contribute to the understanding of the relationships between psychosocial factors

and MSDs. Carayon et al. (1999) underline the role of psychophysiological mechanisms

(e.g. the effects of stress hormones, changes in regional blood flow). Workstyle is featured

in the Feuerstein (1996) model. Melin and Lundberg (1997) highlighted the influence of

demands outside the workplace. However, empirical support to the schemas of the theories

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is limited and further research is needed to validate the multiple pathways that are

proposed.

The current study was based on the ecological model of Sauter and Swanson (1996),

which incorporates three components: psychosocial, biomechanical, and cognitive. The

cognitive component related to the attribution or interpretation of symptoms is a unique

aspect, as well as the proposition that tissue damage is not a necessary condition for the

development of symptoms. The model suggests that a complex cognitive process, which

involves the detection and attribution of symptoms, mediates the relationships between

biomechanical strain and the development of MSDs. The development of symptoms is

seen as a flexible and interpretative process, influenced by both the social context and the

subject's own experience.

The results of this study support the importance of this cognitive component. Pain and

psychosocial factors seem to be reciprocally linked together. There are individual

differences e.g. in pain sensitivity or the manner of experiencing the psychosocial working

environment. Many factors such as coping mechanisms, beliefs, motivation, past pain

history, other life experiences, personality, life situation, etc. can modify these individual

perceptions. The present results suggest that pain modifies the perceptions of psychosocial

factors, and that psychosocial factors modify pain perception. The model (Sauter and

Swanson 1996) shows these reciprocal links between MSDs, work organization and

psychological strain mediated by the cognitive process.

The perception of pain may also modify perceived physical workload. Physical activity, in

terms of biomechanical exposure at work or leisure time, may influence pain perception.

In the model (Sauter and Swanson 1996), the link between MSDs and biomechanical load

is neither direct nor reciprocal. The possible reciprocal associations between perceived

physical workload and pain experiences would be worthy of further study. If that link

would prove reciprocal, it would further strengthen the importance of individual

sensations and cognition in the development of MSDs. As a corollary, interventions

should focus on secondary and tertiary prevention, to guide people to manage and control

disorders whenever they appear.

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8. CONCLUSIONS

While this PE intervention was successful in engaging the kitchen workers to evaluate and

improve the ergonomics of their daily work, no systematic differences in any health

outcomes were found between the intervention and control groups during the intervention

or during the 12-month post-intervention follow-up. The intervention did not reduce

perceived physical workload. The effects on psychosocial factors at work were

unfavorable. These adverse changes were mainly due to a joint effect of the intervention

and unconnected organizational reforms of foodservice in two of the participating cities.

This may partly explain why the intervention did not have any effect on the occurrence of

MSDs. The occurrence of MSP among female kitchen workers was high and more

common than single-site pain. Psychosocial factors at work and mental stress strongly

predicted MSP over time and, vice versa, MSP predicted psychosocial factors and mental

stress. Such reciprocality of the relationships suggests either two mutually dependent

processes in time, or some common underlying factor(s).

9. IMPLICATIONS OF THE RESULTS

The challenges in MSD research and in preventive work include the multifactorial

etiology, the high occurrence of many MSDs and particularly that of MSP, and the

episodic, recurrent and subjective nature of musculoskeletal pain. The workforce is ageing

in the industrialized countries. At the same time, there is pressure to extend working

careers beyond the current retirement age. Interventions that focus on maintaining

employees' work ability, controlling sick leaves, and supporting return to work are needed.

The results do not support the usefulness of the studied PE intervention in preventing

MSDs or in changing unsatisfactory psychosocial working conditions. If organizational

changes are expected to occur, it is essential to take caution with the implementation of

other workplace interventions at the same time. Developing ergonomics should be a

continuous activity in fluent collaboration with planners, architects, technical staff,

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management, and workers themselves as the best expert in their own work. Further high

quality trials are needed to elucidate the effectiveness of ergonomics interventions. The

current study showed that conducting RCT at workplaces is feasible.

The evaluation and prevention of pain at multiple anatomical sites might be useful in

addition to considering single-site pain, both in the daily work of occupational and

healthcare professionals, in epidemiological research, and in further intervention studies.

Since MSP and psychosocial factors at work seem to be strongly linked together, parallel

assessment of both measures is recommended. As subjective perceptions, they may share

some common underlying factors, which need to be clarified in further studies. More

objective methodological approaches for assessing psychosocial factors at work and of

MSDs are also needed.

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ACKNOWLEDGEMENTS

The present work is based on the 'ERGO-study' conducted in the Finnish Institute of

Occupational Health. The Academy of Finland, the Local Government Pensions

Institution, the Ministry of Labour, and the Finnish Work Environment Fund financially

supported the study. The last mentioned one also granted me a one year personal award.

The Finnish Cultural Foundation has awarded me a one year scholarship to complete the

thesis and for post-doctoral studies. They are all gratefully acknowledged. I also thank the

Institute for placing the facilities at my disposal.

I wish to acknowledge the collaborative kitchen workers and representatives of food

services in Espoo, Tampere, Turku and Vantaa, for participating in and their commitment

to the study. I want to express my warmest thanks to all members of the ERGO research

group. I have had the privilege of working in this excellent team that has shared its

scientific expertise and experience with me. I am in debt to many people for their

contributions during different phases of this study.

I am deeply grateful to my supervisors, the leader of ERGO study, Professor (emerita)

Hilkka Riihimäki, and Docent Päivi Leino-Arjas, for their sincere interest in this work and

patiently giving me such skilful guidance. Despite their many duties, they have found time

for discussions essential to push my work forward. They both have encouraged me,

offered advice and constructive comments when needed, but also given possibilities to

think and work independently. Hilkka, your endless optimism and trust on my work were

invaluable, and Päivi, your knowledge on scientific writing is beyond compare. Both of

you introduced me to the world of epidemiology and musculoskeletal research. I have

learnt so much from you.

I wish to warmly thank all my co-authors of the original papers included in this thesis for

co-operation. I offer special thanks to Eira Viikari-Juntura for her valuable comments on

all my four papers, to Esa-Pekka Takala for his advice, encouraging attitude, and

providing help when needed, and to Antti Malmivaara for his expertise in randomized

trials. I owe much to Pertti Mutanen, Elina Nykyri, Svetlana Solovieva, and especially to

Anneli Ojajärvi, for their expert knowledge and advice in statistics during the study.

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Anneli, your talent to take over the challenging analyses, in particular with respect to the

fourth paper, was admirable. Irmeli Pehkonen, my closest co-author and a fellow student,

has always understood me without words. Thank you for your friendship and sharing this

'journey' with me. I also wish to thank my other colleagues in the Institute for their

support.

My sincere thanks belong to the official reviewers, Professor Clas-Håkan Nygård and

Docent Simo Taimela, for their valuable suggestions for improving the manuscript, as well

as to Ewen MacDonald for rapid revision of the language. Professor Allard van der Beek

is warmly acknowledged for accepting the appointment of being my opponent.

Finally, I am most grateful to my family and friends. I could not have completed this work

without their encouragement. My deepest thanks go to my beloved husband Veli, for his

love, inconceivable patience, and support, spurring me on throughout this work especially

during hard times. Words cannot express my feelings for our lovely children, Milla and

Miska, both of them born during these 'ERGO- years'. Their love and existence is more

meaningful to me than anything. I dedicate this work to them.

Espoo, September 2010

Eija Haukka

110

REFERENCES

Aas RW, Holte KA, Labriola M, Lund T, Tuntland H, Røe C, Merkus S, Moller A, Marklund S. Workplace

interventions for low-back pain in workers (protocol). Cochrane Database of Systematic Reviews

2009a (4).

Aas RW, Holte KA, Tuntland H, Røe C, Labriola M, Lund T, Moller A, Skaugen BH, Marklund S.

Workplace interventions for neck pain in workers (protocol). Cochrane Database of Systematic

Reviews 2009b (4).

Adamson G, Murphy S, Shevlin M, Buckle P, Stubbs D. Profiling schoolchildren in pain and associated

demographic and behavioural factors: a latent class approach. Pain 2007;129(3):295-303.

Aggarwal VR, McBeth J, Zakrzewska JM, Lunt M, Macfarlane GJ. The epidemiology of chronic syndromes

that are frequently unexplained: do they have common associated factors? Int J Epidemiol

2006;35(2):468-476.

Alexopoulos EC, Stathi IC, Charizani F. Prevalence of musculoskeletal disorders in dentists. BMC

Musculoskeletal Disorders 2004;5(1):16.

Ammendolia C, Kerr MS, Bombardier C. Back belt use for prevention of occupational low back pain: a

systematic review. J Manipulative Physiol Ther 2005;28(2):128-134.

Andersson H, Ejlertsson G, Leden I. Widespread musculoskeletal chronic pain associated with smoking. An

epidemiological study in a general rural population. Scand J Rehabil Med 1998;30(3):185-191.

Andersson HI. The course of non-malignant chronic pain: a 12-year follow-up of a cohort from the general

population. Eur J Pain 2004;8(1):47-53.

Ariëns GA, van Mechelen W, Bongers PM, Bouter LM, van der Wal G. Psychosocial risk factors for neck

pain: a systematic review. Am J Ind Med 2001;39(2):180-193.

Atienza AA, King AC. Community-based health intervention trials: an overview of methodological issues.

Epidemiol Rev 2002;24(1):72-79.

Auvinen JP, Paananen MV, Tammelin TH, Taimela SP, Mutanen PO, Zitting PJ, Karppinen JI.

Musculoskeletal pain combinations in adolescents. Spine (Phila Pa 1976) 2009;34(11):1192-1197.

Bakker EW, Verhagen AP, Van Trijffel E, Lucas C, Koes BW. Spinal mechanical load as a risk factor for

low back pain: a systematic review of prospective cohort studies. Spine 2009;34(8):E281-293.

Baldwin ML. Reducing the costs of work-related musculoskeletal disorders: targeting strategies to chronic

disability cases. J Electromyogr Kinesiol 2004;14(1):33-41.

Bambra C, Egan M, Thomas S, Petticrew M, Whitehead M. The psychosocial and health effects of

workplace reorganisation. 2. A systematic review of task restructuring interventions. J Epidemiol

Community Health 2007;61(12):1028-1037.

Barrero LH, Katz JN, Dennerlein JT. Validity of self-reported mechanical demands for occupational

epidemiologic research of musculoskeletal disorders. Scand J Work Environ Health

2009;35(4):245-260.

Battie MC, Videman T, Levalahti E, Gill K, Kaprio J. Heritability of low back pain and the role of disc

degeneration. Pain 2007;131(3):272-280.

111

Bernard B. Musculoskeletal disorders and workplace factors. A critical review of epidemiologic evidence

for work-related musculoskeletal disorders of the neck, upper extremity and low back. U.S.

Department of Health and Human Services CDC (NIOSH), DHHS (NIOSH). Publication No. 97-

141. Cincinnati,1997. http://www.cdc.gov/niosh/docs/97-141/ (accessed 10 September 2010).

Bevan S, Quadrello T, McGee R, Mahdon M, Vavrovsky A, Barham L. Fit for work? Musculoskeletal

disorders in the European workforce. London: The Work Foundation, 2009.

http://www.theworkfoundation.com/Assets/Docs/Fit%20for%20Work%20pan-

European%20report.pdf (accessed 10 September 2010).

Bierma-Zeinstra SM, Koes BW. Risk factors and prognostic factors of hip and knee osteoarthritis. Nat Clin

Pract Rheumatol 2007;3(2):78-85.

Bigos SJ, Holland J, Holland C, Webster JS, Battie M, Malmgren JA. High-quality controlled trials on

preventing episodes of back problems: systematic literature review in working-age adults. Spine J

2009;9(2):147-168.

Bingefors K, Isacson D. Epidemiology, co-morbidity, and impact on health-related quality of life of self-

reported headache and musculoskeletal pain - a gender perspective. European Journal of Pain

2004;8(5):435-450.

Blatter B, Bongers PM. Work related neck and upper limb symptoms (RSI): High risk occupations and risk

factors in the Dutch working population. TNO-report 4070117/r9800293. Hoofddorp: TNO

Work,1999. http://www.arbobondgenoten.nl/arbothem/lichblst/rsi/enquete2000/tnorapport.pdf

(accessed 10 September 2010).

Bohr PC. Efficacy of office ergonomics education. Journal of Occupational Rehabilitation 2000;10(4):243-

255.

Bohr PC. Office ergonomics education: a comparison of traditional and participatory methods. Work

2002;19(2):185-191.

Bonate P. Analysis of pretest-posttest designs. USA: Chapman & Hall/CRC, 2000:105-110.

Bongers PM. Are ergonomic interventions effective and worth the cost in preventing or reducing MSDs?.

Proceedings of the 17th World Congress on Ergonomics, International Ergonomics Association

(IEA); August 9-14, 2009, Beijing, China [CD-ROM].

Bongers PM, de Winter CR, Kompier MA, Hildebrandt VH. Psychosocial factors at work and

musculoskeletal disease. Scand J Work Environ Health 1993;19(5):297-312.

Bongers PM, Ijmker S, van den Heuvel S, Blatter BM. Epidemiology of work related neck and upper limb

problems: Psychosocial and personal risk factors (Part I) and effective interventions from a bio

behavioural perspective (Part II). J Occup Rehabil 2006;16(3):272-295.

Bongers PM, Kremer AM, ter Laak J. Are psychosocial factors, risk factors for symptoms and signs of the

shoulder, elbow, or hand/wrist?: A review of the epidemiological literature. Am J Ind Med

2002;41(5):315-342.

Boocock MG, McNair PJ, Larmer PJ, Armstrong B, Collier J, Simmonds M, Garrett N. Interventions for the

prevention and management of neck/upper extremity musculoskeletal conditions: a systematic

review. Occup Environ Med 2007;64(5):291-303.

112

Bos EH, Krol B, Van Der Star A, Groothoff JW. The effects of occupational interventions on reduction of

musculoskeletal symptoms in the nursing profession. Ergonomics 2006;49(7):706-723.

Braunholtz DA, Edwards SJ, Lilford RJ. Are randomized clinical trials good for us (in the short term)?

Evidence for a "trial effect". J Clin Epidemiol 2001;54(3):217-224.

Brewer S, van Eerd D, Amick BC III, Irvin E, Daum KM, Gerr F, Moore JS, Cullen K, Rempel D.

Workplace interventions to prevent musculoskeletal and visual symptoms and disorders among

computer users: a systematic review. J Occup Rehabil 2006;16(3):325-358.

Brown O. Participatory ergonomics (PE). In: Stanton N, Hedge A, Brookhuis K, Salas E, Hendrick H, eds.

Handbook of human factors and ergonomics methods. USA: CRC Press, 2005:81-1-81-7.

Buchholz B, Park JS, Gold JE, Punnett L. Subjective ratings of upper extremity exposures: inter-method

agreement with direct measurement of exposures. Ergonomics 2008;51(7):1064-1077.

Buckle P. Ergonomics and musculoskeletal disorders: overview. Occup Med (Lond) 2005;55(3):164-167.

Buckle PW, Devereux JJ. The nature of work-related neck and upper limb musculoskeletal disorders. Appl

Ergon 2002;33(3):207-217.

Burdorf A. The role of assessment of biomechanical exposure at the workplace in the prevention of

musculoskeletal disorders. Scand J Work Environ Health 2010;36(1):1-2.

Burdorf A, Sorock G. Positive and negative evidence of risk factors for back disorders. Scand J Work

Environ Health 1997;23(4):243-256.

Buring JE. Special issues related to randomized trials of primary prevention. Epidemiol Rev 2002;24(1):67-

71.

Burton AK, Balague F, Cardon G, Eriksen HR, Henrotin Y, Lahad A, Leclerc A, Muller G, van der Beek

AJ. Chapter 2. European guidelines for prevention in low back pain: November 2004. Eur Spine J

2006;15 Suppl 2:S136-168.

Campbell M, Grimshaw J, Steen N. Sample size calculations for cluster randomised trials. Changing

Professional Practice in Europe Group (EU BIOMED II Concerted Action). J Health Serv Res

Policy 2000;5(1):12-16.

Campbell MK, Elbourne DR, Altman DG. CONSORT statement: extension to cluster randomised trials.

Bmj 2004;328(7441):702-708.

Carayon P, Smith MJ, Haims MC. Work organization, job stress, and work-related musculoskeletal

disorders. Hum Factors 1999;41(4):644-663.

Carnes D, Parsons S, Ashby D, Breen A, Foster NE, Pincus T, Vogel S, Underwood M. Chronic

musculoskeletal pain rarely presents in a single body site: results from a UK population study.

Rheumatology (Oxford) 2007;46(7):1168-1170.

Chen SM, Liu MF, Cook J, Bass S, Lo SK. Sedentary lifestyle as a risk factor for low back pain: a

systematic review. Int Arch Occup Environ Health 2009;82(7):797-806.

Christmansson M, Friden J, Sollerman C. Task design, psycho-social work climate and upper extremity pain

disorders - effects of an organisational redesign on manual repetitive assembly jobs. Appl Ergon

1999;30(5):463-472.

113

Coghill RC, McHaffie JG,Yen YF. Neural correlates of interindividual differences in the subjective

experience of pain. Proc Natl Acad Sci U S A 2003;100(14):8538-8542.

Cole D, Rivilis I. Individual factors and musculoskeletal disorders. In: Marras W, Karwowski W, eds.

Fundamentals and assessment tools for occupational ergonomics. The occupational ergonomics

handbook. 2nd edn. New York: Taylor & Francis, 2006:19-1-19-10.

Cole D, Rivilis I, van Eerd D, Cullen K, Kramer D. Effectiveness of participatory ergonomic interventions: a

systematic review. Overview. Toronto: Institute for Work & Health, 2005.

Cole DC,van Eerd D, Bigelow P, Rivilis I. Integrative interventions for MSDs: nature, evidence, challenges

& directions. J Occup Rehabil 2006;16(3):359-374.

Cole DC, Wells RP, Frazer MB, Kerr MS, Neumann WP, Laing AC. Methodological issues in evaluating

workplace interventions to reduce work-related musculoskeletal disorders through mechanical

exposure reduction. Scand J Work Environ Health 2003;29(5):396-405.

Côté P, van der Velde G, Cassidy JD, Carroll LJ, Hogg-Johnson S, Holm LW, Carragee EJ, Haldeman S,

Nordin M, Hurwitz EL, Guzman J, Peloso PM. The burden and determinants of neck pain in

workers: results of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its

Associated Disorders. Spine (Phila Pa 1976) 2008;33(4 Suppl):S60-74.

Croft P. The question is not "have you got it"? But "how much of it have you got"? Pain 2009;141(1-2):6-7.

Croft P, Dunn KM, Von Korff M. Chronic pain syndromes: you can't have one without another. Pain

2007;131(3):237-238.

D'Souza JC, Franzblau A, Werner RA. Review of epidemiologic studies on occupational factors and lower

extremity musculoskeletal and vascular disorders and symptoms. J Occup Rehabil 2005;15(2):129-

165.

Davies HT, Crombie IK, Macrae WA. Where does it hurt? Describing the body locations of chronic pain.

Eur J Pain 1998;2(1):69-80.

Davis KG, Heaney CA.The relationship between psychosocial work characteristics and low back pain:

underlying methodological issues. Clin Biomech (Bristol, Avon) 2000;15(6):389-406.

de Zwart BC, Broersen JP, Frings-Dresen MH, van Dijk FJ. Repeated survey on changes in musculoskeletal

complaints relative to age and work demands. Occupational and environmental medicine

1997;54(11):793-799.

Demure B, Mundt KA, Bigelow C, Luippold RS, Ali D, Liese B. Video display terminal workstation

improvement program: II. Ergonomic intervention and reduction of musculoskeletal discomfort. J

Occup Environ Med 2000;42(8):792-797.

Donner A, Klar N. Design and analysis of cluster randomization trials in health research. London: Arnold,

2000.

Driessen MT, Anema JR, Proper KI, Bongers PM, van der Beek AJ. Stay@Work: Participatory Ergonomics

to prevent low back and neck pain among workers: design of a randomised controlled trial to

evaluate the (cost-) effectiveness. BMC Musculoskelet Disord 2008;9:145.

114

Driessen MT, Proper KI, van Tulder MW, Anema JR, Bongers PM, van der Beek AJ. The effectiveness of

physical and organisational ergonomic interventions on low back pain and neck pain: a systematic

review. Occupational and environmental medicine 2010;67(4):277-285.

Egan M, Bambra C, Thomas S, Petticrew M, Whitehead M, Thomson H. The psychosocial and health

effects of workplace reorganisation. 1. A systematic review of organisational-level interventions

that aim to increase employee control. J Epidemiol Community Health 2007;61(11):945-954.

Elo A-L, Leppänen A, Lindström K, Ropponen T. OSQ-occupational stress questionnaire: user´s

instructions (reviews 19). Helsinki: Finnish Institute of Occupational Health, 1992.

Elo A-L, Leppänen A, Jahkola A.Validity of a single-item measure of stress symptoms. Scand J Work

Environ Health 2003;29(6):444-451.

Elo A-L, Leppänen A, Lindström K, Ropponen T. The Occupational Sress Questionnaire. In: Zenz C,

Dickerson O, Horvath E, eds. Occupational Medicine. 3rd edn. St.Louis: MO Mosby, 1994:1234-

1237.

EPIQ. A Generic Appraisal Tool for Epidemiology (GATE). 2004.

http://user.meduni-graz.at/andrea.berghold/EBM/Gate_Notes.pdf (accessed 10 September 2010).

European Agency for Safety and Health at Work. E-facts 24. Musculoskeletal disorders (MSDs) in

HORECA. Publishing date 11.1. 2008. http://osha.europa.eu/en/publications/e-facts/efact24

(accessed 10 September 2010).

Evanoff BA, Bohr PC, Wolf LD. Effects of a participatory ergonomics team among hospital orderlies. Am J

Ind Med 1999;35(4):358-365.

Fejer R, Hartvigsen J, Kyvik KO. Heritability of neck pain: a population-based study of 33,794 Danish

twins. Rheumatology (Oxford) 2006;45(5):589-594.

Feuerstein M.Work style: definition, empirical support, and implications for prevention, evaluation, and

rehabilitation of occupational upper-extremity disorders. In: Moon SD, Sauter SL, eds. Beyond

Biomechanics: psychosocial aspects of musculoskeletal disorders in office work. Bristol, PA:

Taylor and Francis, 1996:177-206.

Feuerstein M, Marshall L, Shaw WS, Burrell LM. Multicomponent intervention for work-related upper

extremity disorders. Journal of Occupational Rehabilitation 2000;10(1):71-83.

Finnish Centre for Pensions. Statistical yearbook of pensioners in Finland, 2007. Helsinki: Edita Prima Oy,

2008.

Forma P. Incidence of disability pensions among municipal occupational groups from 1995 to 2001 In:

Forma P, Blomster P, Halmeenmäki T, Peltonen H, Tiilikka T. Articles about the municipal

pensions system (in Finnish). Helsinki: The Local Government Pensions Institution, 2004:54-71.

Franceshi S, Plummer M. Intervention trials. In: Ahrens W, Pigeot I, eds. Handbook of epidemiology.

Berlin: Springer, 2005;345-370.

Fredriksson K, Bildt C, Hagg G, Kilbom A. The impact on musculoskeletal disorders of changing physical

and psychosocial work environment conditions in the automobile industry. International Journal of

Industrial Ergonomics 2001;28(1):31-45.

115

Gatty CM, Turner M, Buitendorp DJ, Batman H. The effectiveness of back pain and injury prevention

programs in the workplace. Work 2003;20(3):257-266.

Goldenhar LM, LaMontagne AD, Katz T, Heaney C, Landsbergis P. The intervention research process in

occupational safety and health: an overview from the National Occupational Research Agenda

Intervention Effectiveness Research team. J Occup Environ Med 2001;43(7):616-622.

Goldenhar LM, Schulte PA. Methodological issues for intervention research in occupational health and

safety. Am J Ind Med 1996;29(4):289-294.

Gran JT. The epidemiology of chronic generalized musculoskeletal pain. Best Pract Res Clin Rheumatol

2003;17(4):547-561.

Green SB. Design of randomized trials. Epidemiol Rev 2002;24(1):4-11.

Grimshaw J, Campbell M, Eccles M, Steen N. Experimental and quasi-experimental designs for evaluating

guideline implementation strategies. Fam Pract 2000;17 Suppl 1:S11-16.

Hagberg M. Clinical assessment of musculoskeletal disorders in workers exposed to hand-arm vibration. Int

Arch Occup Environ Health 2002;75(1-2):97-105.

Hagberg M, Silverstein B, Wells R, Smith M, Hendrick H, Carayon P, Pérusse M. In: Kuorinka I, Forcier L,

eds. Work related musculoskeletal disorders (WMSDs): a reference book for prevention. London:

Taylor & Francis, 1995.

Hagen EM, Svensen E, Eriksen HR, Ihlebaek CM, Ursin H. Comorbid subjective health complaints in low

back pain. Spine 2006;31(13):1491-1495.

Haims MC, Carayon P. Theory and practice for the implementation of 'in-house', continuous improvement

participatory ergonomic programs. Appl Ergon 1998;29(6):461-472.

Haines H, Wilson J. Development of a framework for participatory ergonomics. Health and Safety

executive. Contract Research Report 174/1998. London: HSE Books, 1998.

http://www.hse.gov.uk/research/crr_pdf/1998/crr98174.pdf (accessed 10 September 2010)

Hamberg-van Reenen HH, Ariens GA, Blatter BM, van Mechelen W, Bongers PM. A systematic review of

the relation between physical capacity and future low back and neck/shoulder pain. Pain

2007;130(1-2):93-107.

Hansson T, Westerholm P, (red). Arbete och besvär i rörelseorganen. En vetenskaplig värdering av frågor

om samband. Stockholm: Arbete och Hälsa, Arbetslivsinstitutet 2001;12.

Harkness EF, Macfarlane GJ, Nahit E, Silman AJ, McBeth J. Mechanical injury and psychosocial factors in

the work place predict the onset of widespread body pain: a two-year prospective study among

cohorts of newly employed workers. Arthritis Rheum 2004;50(5):1655-1664.

Harkness EF, Macfarlane GJ, Nahit ES, Silman AJ, McBeth J. Mechanical and psychosocial factors predict

new onset shoulder pain: a prospective cohort study of newly employed workers. Occup Environ

Med 2003;60(11):850-857.

Hartvigsen J, Lings S, Leboeuf-Yde C, Bakketeig L. Psychosocial factors at work in relation to low back

pain and consequences of low back pain; a systematic, critical review of prospective cohort studies.

Occup Environ Med 2004;61(1):e2.

116

Hartvigsen J, Nielsen J, Kyvik KO, Fejer R, Vach W, Iachine I, Leboeuf-Yde C. Heritability of spinal pain

and consequences of spinal pain: a comprehensive genetic epidemiologic analysis using a

population-based sample of 15,328 twins ages 20-71 years. Arthritis Rheum 2009;61(10):1343-

1351.

Hartvigsen J, Petersen HC, Frederiksen H, Christensen K. Small effect of genetic factors on neck pain in old

age: a study of 2,108 Danish twins 70 years of age and older. Spine (Phila Pa 1976)

2005;30(2):206-208.

Heaney C, Fujishiro K. Psychosocial characteristics of work as targets for change. In: Marras WS,

Karwowski W, eds. Interventions, controls, and applications in occupational ergonomics. The

occupational ergonomics handbook. 2nd edn. New York: Taylor & Francis, 2006;25-1-25-14.

Hignett S, Wilson JR, Morris W. Finding ergonomic solutions - participatory approaches. Occup Med

(Lond) 2005;55(3):200-207.

Hogg-Johnson S, van der Velde G, Carroll LJ, Holm LW, Cassidy JD, Guzman J, Côté P, Haldeman S,

Ammendolia C, Carragee E, Hurwitz E, Nordin M, Peloso P. The burden and determinants of neck

pain in the general population: results of the Bone and Joint Decade 2000-2010 Task Force on Neck

Pain and Its Associated Disorders. Spine (Phila Pa 1976) 2008;33(4 Suppl):S39-51.

Hooftman WE, van Poppel MN, van der Beek AJ, Bongers PM, van Mechelen W. Gender differences in the

relations between work-related physical and psychosocial risk factors and musculoskeletal

complaints. Scand J Work Environ Health 2004;30(4):261-278.

Hoogendoorn WE, van Poppel MN, Bongers PM, Koes BW, Bouter LM. Physical load during work and

leisure time as risk factors for back pain. Scand J Work Environ Health 1999;25(5):387-403.

Hoogendoorn WE, van Poppel MN, Bongers PM, Koes BW, Bouter LM. Systematic review of psychosocial

factors at work and private life as risk factors for back pain. Spine 2000;25(16):2114-2125.

Hooper MM. Tending to the musculoskeletal problems of obesity. Cleve Clin J Med 2006;73(9):839-845.

Huang GD, Feuerstein M, Sauter SL. Occupational stress and work-related upper extremity disorders:

concepts and models. Am J Ind Med 2002;41(5):298-314.

Huang J, Ono Y, Shibata E, Takeuchi Y, Hisanaga N. Occupational musculoskeletal disorders in lunch

centre workers. Ergonomics 1988;31(1):65-75.

Ijzelenberg W, Burdorf A. Impact of musculoskeletal co-morbidity of neck and upper extremities on

healthcare utilisation and sickness absence for low back pain. Occup Environ Med

2004;61(10):806-810.

Imada AS. The rationale and tools of participatory ergonomics. In: Noro K, Imada A.S, eds. Participatory

ergonomics. London: Taylor & Francis, 1991:30-51.

Irving DB, Cook JL, Menz HB. Factors associated with chronic plantar heel pain: a systematic review. J Sci

Med Sport 2006;9(1-2):11-22; discussion 23-14.

IWH. Factors for success in participatory ergonomics. Institute for Work & Health, 2008.

http://www.iwh.on.ca/sbe/factors-for-success-in-participatory-ergonomics (accessed 10 September

2010).

117

Jellema P, van Tulder MW, van Poppel MN, Nachemson AL, Bouter LM. Lumbar supports for prevention

and treatment of low back pain: a systematic review within the framework of the Cochrane Back

Review Group. Spine (Phila Pa 1976) 2001;26(4):377-386.

Jensen LK. Hip osteoarthritis: influence of work with heavy lifting, climbing stairs or ladders, or combining

kneeling/squatting with heavy lifting. Occup Environ Med 2008a;65(1):6-19.

Jensen LK. Knee osteoarthritis: influence of work involving heavy lifting, kneeling, climbing stairs or

ladders, or kneeling/squatting combined with heavy lifting. Occup Environ Med 2008b;65(2):72-

89.

Jones BL, Nagin DS. Advances in group-based trajectory modeling and an SAS procedure for estimating

them. Sociological Methods & Research 2007;35(4):542-571.

Jones GT, Silman AJ, Macfarlane GJ. Predicting the onset of widespread body pain among children.

Arthritis Rheum 2003;48(9):2615-2621.

Jüni P, Altman DG, Egger M. Systematic reviews in health care: Assessing the quality of controlled clinical

trials. Bmj 2001;323(7303):42-46.

Kaila-Kangas L, ed. Musculoskeletal disorders and diseases in Finland - results of the Health 2000 Survey.

Publications of the National Public Health Institute B 25. Helsinki, 2007.

Kalichman L, Hunter DJ. The genetics of intervertebral disc degeneration. Familial predisposition and

heritability estimation. Joint Bone Spine 2008;75(4):383-387.

Kamaleri Y, Natvig B, Ihlebaek CM, Benth JS, Bruusgaard D. Number of pain sites is associated with

demographic, lifestyle, and health-related factors in the general population. Eur J Pain

2008a;12(6):742-748.

Kamaleri Y, Natvig B, Ihlebaek CM, Benth JS, Bruusgaard D. Change in the number of musculoskeletal

pain sites: A 14-year prospective study. Pain 2009;141(1-2):25-30.

Kamaleri Y, Natvig B, Ihlebaek CM, Bruusgaard D. Does the number of musculoskeletal pain sites predict

work disability? A 14-year prospective study. Eur J Pain 2008b.

Kamaleri Y, Natvig B, Ihlebaek CM, Bruusgaard D. Localized or widespread musculoskeletal pain: does it

matter? Pain 2008c;138(1):41-46.

Karsh B. Theories of work-related musculoskeletal disorders: implications for ergonomic interventions.

Theoretical Issues in Ergonomics Science 2006;7(1):71-88.

Karsh B, Moro F, Smith M. The efficacy of workplace ergonomic interventions to control musculoskeletal

disorders:a critical analysis of the peer-reviewed literature. Theoretical Issues in Ergonomics

Science 2001;2(1):23-96.

Kauppila LI. Atherosclerosis and disc degeneration/low-back pain--a systematic review. Eur J Vasc

Endovasc Surg 2009;37(6):661-670.

Ketola R, Toivonen R, Häkkänen M, Luukkonen R, Takala EP, Viikari-Juntura E. Effects of ergonomic

intervention in work with video display units. Scand J Work Environ Health 2002;28(1):18-24.

Kobayashi Y, Kaneyoshi A, Yokota A, Kawakami N. Effects of a worker participatory program for

improving work environments on job stressors and mental health among workers: a controlled trial.

J Occup Health 2008;50(6):455-470.

118

Kogi K. Participatory methods effective for ergonomic workplace improvement. Appl Ergon

2006;37(4):547-554.

Kokko K. An applied viewpoint to the trajectory analysis method (in Finnish). Psykologia 2004;39:424-433.

Kristensen TS. Intervention studies in occupational epidemiology. Occup Environ Med 2005;62(3):205-210.

Kuorinka I, Jonsson B, Kilbom A, Vinterberg H, Biering-Sorenson F, Anderson G, Jorgensen K.

Standardised Nordic Questionnaires for the analysis of musculoskeletal symptoms. Appl Ergon

1987;18:233-237.

Kuorinka I. Tools and means of implementing participatory ergonomics. International Journal of Industrial

Ergonomics 1997;19(4):267-270.

Lagerström M, Josephson M, Pingel B, Tjernstrom G, Hagberg M, Grp MS. Evaluation of the

implementation of an education and training programme for nursing personnel at a hospital in

Sweden. International Journal of Industrial Ergonomics 1998;21(1):79-90.

Laine S, Gimeno D, Virtanen M, Oksanen T, Vahtera J, Elovainio M, Koskinen A, Pentti J, Kivimäki M.

Job strain as a predictor of disability pension: the Finnish Public Sector Study. J Epidemiol

Community Health 2009;63(1):24-30.

Laing AC, Cole DC, Theberge N, Wells RP, Kerr MS, Frazer MB. Effectiveness of a participatory

ergonomics intervention in improving communication and psychosocial exposures. Ergonomics

2007;50(7):1092-1109.

Laing AC, Frazer MB, Cole DC, Kerr MS, Wells RP, Norman RW. Study of the effectiveness of a

participatory ergonomics intervention in reducing worker pain severity through physical exposure

pathways. Ergonomics 2005;48(2):150-170.

Larsson B, Sund AM. Emotional/behavioural, social correlates and one-year predictors of frequent pains

among early adolescents: influences of pain characteristics. Eur J Pain 2007;11(1):57-65.

Leboeuf-Yde C, Nielsen J, Kyvik KO, Fejer R, Hartvigsen J. Pain in the lumbar, thoracic or cervical

regions: do age and gender matter? A population-based study of 34,902 Danish twins 20-71 years

of age. BMC Musculoskelet Disord 2009;10:39.

Leino-Arjas P, Solovieva S, Riihimäki H, Kirjonen J, Telama R. Leisure time physical activity and

strenuousness of work as predictors of physical functioning: a 28 year follow up of a cohort of

industrial employees. Occup Environ Med 2004;61(12):1032-1038.

Leino P, Magni G.Depressive and distress symptoms as predictors of low back pain, neck-shoulder pain, and

other musculoskeletal morbidity: a 10-year follow-up of metal industry employees. Pain

1993;53(1):89-94.

Leino PI, Hänninen V. Psychosocial factors at work in relation to back and limb disorders. Scand J Work

Environ Health 1995;21(2):134-142.

Leppänen A. Improving the mastery of work and the development of the work process in paper production.

Relations Industrielles/ Industrial Relations 2001;56(3):579-609.

Liang K-Y, Zeger SL. Longitudinal data analysis using generalized linear models. Biometrika 1986;73:13-

22.

119

Lincoln AE, Vernick JS, Ogaitis S, Smith GS, Mitchell CS, Agnew J. Interventions for the primary

prevention of work-related carpal tunnel syndrome. Am J Prev Med 2000;18(4 Suppl):37-50.

Linton SJ. Occupational psychological factors increase the risk for back pain: a systematic review. J Occup

Rehabil 2001;11(1):53-66.

Linton SJ, van Tulder MW. Preventive interventions for back and neck pain problems: what is the evidence?

Spine 2001;26(7):778-787.

Lis AM, Black KM, Korn H, Nordin M. Association between sitting and occupational LBP. Eur Spine J

2007;16(2):283-298.

Lötters F, Burdof A. Are changes in mechanical exposure and musculoskeletal health good performance

indicators for primary interventions? Int Arch Occup Environ Health 2002;75(8):549-561.

Macfarlane GJ, Hunt IM, Silman AJ. Role of mechanical and psychosocial factors in the onset of forearm

pain: prospective population based study. Bmj 2000;321(7262):676-679.

Macfarlane GJ, Pallewatte N, Paudyal P, Blyth FM, Coggon D, Crombez G, Linton S, Leino-Arjas P,

Silman AJ, Smeets RJ, van der Windt D. Evaluation of work-related psychosocial factors and

regional musculoskeletal pain: results from a EULAR Task Force. Ann Rheum Dis

2009;68(6):885-891.

Mallen CD, Peat G, Thomas E, Dunn KM, Croft PR. Prognostic factors for musculoskeletal pain in primary

care: a systematic review. Br J Gen Pract 2007;57(541):655-661.

Marras WS, Cutlip RG, Burt SE, Waters TR.National occupational research agenda (NORA) future

directions in occupational musculoskeletal disorder health research. Appl Ergon 2009;40(1):15-22.

Martimo KP, Verbeek J, Karppinen J, Furlan AD, Takala EP, Kuijer PP, Jauhiainen M, Viikari-Juntura E.

Effect of training and lifting equipment for preventing back pain in lifting and handling: systematic

review. Bmj 2008;336(7641):429-431.

McBeth J, Harkness EF, Silman AJ, Macfarlane GJ.The role of workplace low-level mechanical trauma,

posture and environment in the onset of chronic widespread pain. Rheumatology (Oxford)

2003;42(12):1486-1494.

Medical Research Council. Cluster randomized trials: methodological and ethical considerations. MRC

clinical trials series. London, 2002:1-16.

http://www.mrc.ac.uk/Utilities/Documentrecord/index.htm?d=MRC002406 (accessed 10

September 2010).

Melin B, Lundberg U. A biopsychosocial approach to workstress and musculoskeletal disorders. J

Psychophysiol 1997;11(3):238-247.

Merskey H, Bogduk N. Part III: Pain terms, A Current List with Definitions and Notes on Usage. In:

Merskey H, Bogduk N, eds. Classification of Chronic Pain, IASP Task Force on Taxonomy.

Seattle; IASP Press, 1994:209-213. 3http://www.iasp-

pain.org/AM/Template.cfm?Section=Classification_of_Chronic_Pain&Template=/CM/HTMLDisp

lay.cfm&ContentID=2687#Pain (accessed 10 September 2010)

Messing K, Kilbom A. Standing and very slow walking: foot pain-pressure threshold, subjective pain

experience and work activity. Appl Ergon 2001;32(1):81-90.

120

Mikkelsson M, Kaprio J, Salminen JJ, Pulkkinen L, Rose RJ. Widespread pain among 11-year-old Finnish

twin pairs. Arthritis Rheum 2001;44(2):481-485.

Miranda H, Kaila-Kangas L, Heliövaara M, Leino-Arjas P, Haukka E, Liira J, Viikari-Juntura E.

Musculoskeletal pain at multiple sites and its effects on work ability in a general working

population. Occup Environ Med 2010;67(7):449-455.

Miranda H, Punnett L, Viikari-Juntura E, Heliövaara M, Knekt P. Physical work and chronic shoulder

disorder.Results of a prospective population-based study. Ann Rheum Dis 2008a;67(2):218-223.

Miranda H, Viikari-Juntura E, Martikainen R, Riihimaki H. A prospective study on knee pain and its risk

factors. Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society 2002;10(8):623-630.

Miranda H, Viikari-Juntura E, Martikainen R, Takala EP, Riihimäki H. A prospective study of work related

factors and physical exercise as predictors of shoulder pain. Occup Environ Med 2001;58(8):528-

534.

Miranda H, Viikari-Juntura E, Punnett L, Riihimäki H. Occupational loading, health behavior and sleep

disturbance as predictors of low-back pain. Scand J Work Environ Health 2008b;34(6):411-419.

Molano SM, Burdorf A, Elders LA. Factors associated with medical care-seeking due to low-back pain in

scaffolders. Am J Ind Med 2001;40(3):275-281.

Morken T, Moen B, Riise T, Hauge SHV, Holien S, Langedrag A, Olson HO, Pedersen S, Saue ILL, Seljebo

GM, Thoppil V. Effects of a training program to improve musculoskeletal health among industrial

workers - effects of supervisors role in the intervention. International Journal of Industrial

Ergonomics 2002;30(2):115-127.

Morken T, Riise T, Moen B, Hauge SH, Holien S, Langedrag A, Pedersen S, Saue IL, Seljebo GM, Thoppil

V. Low back pain and widespread pain predict sickness absence among industrial workers. BMC

Musculoskelet Disord 2003;4(1):21.

Murphy LR, Sauter SL. Work organization interventions: state of knowledge and future directions. Soz

Praventivmed 2004;49(2):79-86.

Mäntyselkä P, Kumpusalo E, Ahonen R, Kumpusalo A, Kauhanen J, Viinamäki H, Halonen P, Takala J.

Pain as a reason to visit the doctor: a study in Finnish primary health care. Pain 2001;89(2-3):175-

180.

Mäntyselkä PT, Kumpusalo EA, Ahonen RS, Takala JK. Direct and indirect costs of managing patients with

musculoskeletal pain-challenge for health care. Eur J Pain 2002;6(2):141-148.

Nagamachi M. Requisites and practices of participatory ergonomics. International Journal of Industrial

Ergonomics 1995;15:371-377.

Nagasu M, Sakai K, Ito A, Tomita S, Temmyo Y, Ueno M, Miyagi S. Prevalence and risk factors for low

back pain among professional cooks working in school lunch services. BMC Public Health

2007;7:171.

Nagin DS. Analyzing developmental trajectories: a semiparametric, group-based approach. Psychological

Methods 1999;4(2):139-157.

Nagin DS. Group-based modeling of development. Cambridge, MA: Harvard University Press, 2005.

121

Nahit ES, Hunt IM, Lunt M, Dunn G, Silman AJ, Macfarlane GJ. Effects of psychosocial and individual

psychological factors on the onset of musculoskeletal pain: common and site-specific effects. Ann

Rheum Dis 2003;62(8):755-760.

Nahit ES, Pritchard CM, Cherry NM, Silman AJ, Macfarlane GJ. The influence of work related psychosocial

factors and psychological distress on regional musculoskeletal pain: a study of newly employed

workers. J Rheumatol 2001;28(6):1378-1384.

National Research Council Panel on Musculoskeletal Disorders and the Workplace. Magnitude of

occupationally-related musculoskeletal disorders. In: Marras WS, Karwowski W, eds.

Fundamentals and assessment tools for occupational ergonomics. Occupational ergonomics

handbook. 2nd edn. New York: Taylor & Francis, 2006;2-1-2-21.

National Research Council and Institute of Medicine. Musculoskeletal Disorders and the workplace: low

back and upper extremities. Washington, DC: National Academy Press, 2001.

http://www.nap.edu/catalog.php?record_id=10032 (accessed 10 September 2010).

Natvig B, Eriksen W, Bruusgaard D. Low back pain as a predictor of long-term work disability.

Scandinavian Journal of Public Health 2002;30(4):288-292.

Neumann WP, Eklund J, Hansson B, Lindbeck L. Effect assessment in work environment interventions: a

methodological reflection. Ergonomics 2010;53(1):130-137.

Norlund A, Waddel G. Cost of back pain in some OECD countries. In: Nachemson A, Jonson E, eds. Neck

and back pain: The scientific evidence of causes, diagnosis and treatment. Philadelphia: Lippincott

Williams & Wilkins. 2000:421-425.

Nyman T, Grooten WJ, Wiktorin C, Liwing J, Norrman L. Sickness absence and concurrent low back and

neck-shoulder pain: results from the MUSIC-Norrtalje study. Eur Spine J 2007;16(5):631-638.

Ono Y, Nakamura R, Shimaoka M, Hiruta S, Hattori Y, Ichihara G, Kamijima M, Takeuchi Y. Epicondylitis

among cooks in nursery schools. Occup Environ Med 1998;55(3):172-179.

Ono Y, Shimaoka M, Hiruta S, Takeuchi Y. Low back pain among cooks in nursery schools. Industrial

Health 1997;35(2):194-201.

Paananen MV, Auvinen JP, Taimela SP, Tammelin TH, Kantomaa MT, Ebeling HE, Taanila AM, Zitting

PJ, Karppinen JI. Psychosocial, mechanical, and metabolic factors in adolescents' musculoskeletal

pain in multiple locations: A cross-sectional study. European journal of pain (London, England)

2010;14(4):395-401.Palmer KT, Harris EC, Coggon D. Carpal tunnel syndrome and its relation to occupation: a systematic

literature review. Occupational medicine (Oxford, England) 2007a;57(1):57-66.

Palmer KT, Harris EC, Coggon D. Compensating occupationally related tenosynovitis and epicondylitis: a

literature review. Occupational medicine (Oxford, England) 2007b;57(1):67-74.

Papageorgiou AC, Silman AJ, Macfarlane GJ. Chronic widespread pain in the population: a seven year

follow up study. Ann Rheum Dis 2002;61(12):1071-1074.

Pehkonen I, Ketola R, Ranta R, Takala EP. A video-based observation method to assess musculoskeletal

load in kitchen work. Int J Occup Saf Ergon 2009a;15(1):75-88.

122

Pehkonen I, Miranda H, Haukka E, Luukkonen R, Takala EP, Ketola R, Leino-Arjas P, Riihimäki H,

Viikari-Juntura E. Prospective study on shoulder symptoms among kitchen workers in relation to

self-perceived and observed work load. Occup Environ Med 2009b;66(6):416-423.

Pehkonen I, Takala EP, Ketola R, Viikari-Juntura E, Leino-Arjas P, Hopsu L, Virtanen T, Haukka E,

Holtari-Leino M, Nykyri E, Riihimäki H. Evaluation of a participatory ergonomic intervention

process in kitchen work. Appl Ergon 2009c;40(1):115-123.

Perkiö-Mäkelä M, Hirvonen M, Elo AL, Ervasti J, Huuhtanen P, Kandolin I, Kauppinen K, Kauppinen T,

Ketola R, Lindström K, Manninen P, Mikkola J, Reijula K, Riala R, Salminen S, Toivanen M,

Viluksela M. Work and health survey 2006, Statistics. Helsinki; Finnish Institute of Occupational

Health, 2006.

Picavet HS, Schouten JS. Musculoskeletal pain in the Netherlands: prevalences, consequences and risk

groups, the DMC(3)-study. Pain 2003;102(1-2):167-178.

Podniece Z. Work-related musculoskeletal disorders: prevention report. Luxembourg: European Agency for

Safety and Health at Work, 2008.

http://osha.europa.eu/en/publications/reports/en_TE8107132ENC.pdf (accessed 10 September

2010)

Punnett L, Pruss-Utun A, Nelson DI, Fingerhut MA, Leigh J, Tak S, Phillips S. Estimating the global burden

of low back pain attributable to combined occupational exposures. Am J Ind Med 2005;48(6):459-

469.

Punnett L, Wegman DH. Work-related musculoskeletal disorders: the epidemiologic evidence and the

debate. Journal of Electromyography and Kinesiology 2004;14(1):13-23.

Riihimäki H. Musculoskeletal disorders. In: Ahrens W, Pigeot I, eds. Handbook of epidemiology. Berlin:

Springer, 2005a: 1443-72.

Riihimäki H. Participatory ergonomic intervention at work place: randomized controlled trial and

etnographic study. In: Javanainen M, ed. GEMS of the Health Promotion Research Programme.

Tampere: Juvenes Print, 2005b; 91-100.

Rivilis I, Cole DC, Frazer MB, Kerr MS, Wells RP, Ibrahim S. Evaluation of a participatory ergonomic

intervention aimed at improving musculoskeletal health. Am J Ind Med 2006;49(10):801-810.

Rivilis I, van Eerd D, Cullen K, Cole DC, Irvin E, Tyson J, Mahood Q. Effectiveness of participatory

ergonomic interventions on health outcomes: a systematic review. Appl Ergon 2008;39(3):342-358.

Rothman K, Greenland S. Modern epidemiology. 2nd edn. Philadelphia: Lippincott - Raven Publishers,

1998.

Saastamoinen P, Leino-Arjas P, Laaksonen M, Martikainen P, Lahelma E. Pain and health related

functioning among employees. Journal of Epidemiology and Community Health 2006;60(9):793-

798.

Sauter S, Swanson N. An ecological model of musculoskeletal disorders in office work. In: Moon SD,

Sauter SL, eds. Beyond biomechanics: psychosocial aspects of musculoskeletal disorders in office

work. London: Taylor & Francis, 1996:3-21.

123

Schierhout GH, Myers JE. Is self-reported pain an appropriate outcome measure in ergonomic-

epidemiologic studies of work-related musculoskeletal disorders? Am J Ind Med 1996;30(1):93-98.

Schulte PA, Goldenhar LM, Connally LB. Intervention research: science, skills, and strategies. Am J Ind

Med 1996;29(4):285-288.

Shannon HS, Robson LS, Guastello SJ. Methodological criteria for evaluating occupational safety

intervention research. Safety Science 1999;31:161-179.

Shibata E, Ono Y, Huang J, Hisanaga N, Takeuchi Y, Shimaoka M, Hiruta S. Ergonomics problems among

kitchen workers in nurseries. In: Kumashiro M, Megaw ED, eds. Towards Human Work: Solutions

to Problems in Occupational Health and Safety. London: Taylor & Francis, 1991: 263-268.

Shiri R, Karppinen J, Leino-Arjas P, Solovieva S, Varonen H, Kalso E, Ukkola O, Viikari-Juntura E.

Cardiovascular and lifestyle risk factors in lumbar radicular pain or clinically defined sciatica: a

systematic review. Eur Spine J 2007;16(12):2043-2054.

Shiri R, Karppinen J, Leino-Arjas P, Solovieva S, Viikari-Juntura E. The Association Between Obesity and

Low Back Pain: A Meta-Analysis. Am J Epidemiol 2010a;171(2):135-154.

Shiri R, Karppinen J, Leino-Arjas P, Solovieva S, Viikari-Juntura E. The association between smoking and

low back pain: a meta-analysis. Am J Med 2010b;123(1):87. e87-87.e35.

Shiue HS, Lu CW, Chen CJ, Shih TS, Wu SC, Yang CY, Yang YH, Wu TN. Musculoskeletal disorder

among 52,261 Chinese restaurant cooks cohort: result from the National Health Insurance Data. J

Occup Health 2008;50(2):163-168.

Silverstein B, Clark R. Interventions to reduce work-related musculoskeletal disorders. J Electromyogr

Kinesiol 2004;14(1):135-152.

Solidaki E, Chatzi L, Bitsios P, Markatzi I, Plana E, Castro F, Palmer K, Coggon D, Kogevinas M. Work-

related and psychological determinants of multisite musculoskeletal pain. Scand J Work Environ

Health 2010;36(1):54-61.

St-Vincent M, Bellemare M, Toulouse G, Tellier C. Participatory ergonomic processes to reduce

musculoskeletal disorders: summary of a Quebec experience. Work 2006;27(2):123-135.

Straker L, Burgess-Limerick R, Pollock C, Egeskov R. A randomized and controlled trial of a participative

ergonomics intervention to reduce injuries associated with manual tasks: physical risk and

legislative compliance. Ergonomics 2004;47(2):166-188.

Strazdins L, Bammer G. Women, work and musculoskeletal health. Soc Sci Med 2004;58(6):997-1005.

Streiner DL, Norman GR. Health measurement scales. A practical guide to their development and use. 2nd

edn. Oxford: Oxford University Press, 1995:35

Taimela S, Kaila-Kangas L, Nykyri E, Heliövaara M. Self-rated disability due to musculoskeletal disorders

at work and during leisure time. In: Kaila-Kangas L, ed. Musculoskeletal disorders and diseases in

Finland. Results of the Health 2000 Survey. Publications of the National Public Health Institute

B25. Helsinki:Hakapaino Oy, 2007.

Takala EP, Pehkonen I, Forsman M, Hansson GA, Mathiassen SE, Neumann WP, Sjøgaard G, Veiersted

KB, Westgaard RH, Winkel J. Systematic evaluation of observational methods assessing

biomechanical exposures at work. Scand J Work Environ Health 2010;36(1):3-24.

124

Takala EP, Viikari-Juntura E, Moneta GB, Saarenmaa K, Kaivanto K. Seasonal variation in neck and

shoulder symptoms. Scand J Work Environ Health 1992;18(4):257-261.

Theberge N, Granzow K, Cole D, Laing A. Negotiating participation: understanding the "how" in an

ergonomic change team. Appl Ergon 2006;37(2):239-248.

Theorell T, Hasselhorn HM. On cross-sectional questionnaire studies of relationships between psychosocial

conditions at work and health--are they reliable? Int Arch Occup Environ Health 2005;78(7):517-

522.

The Social Insurance Institution. Statistical Yearbook of the Social Insurance Institution 2007. Official

Statistics of Finland. Helsinki: Vammalan kirjapaino Oy, 2008.

Tsutsumi A, Nagami M, Yoshikawa T, Kogi K, Kawakami N. Participatory intervention for workplace

improvements on mental health and job performance among blue-collar workers: a cluster

randomized controlled trial. J Occup Environ Med 2009;51(5):554-563.

Tveito TH, Hysing M, Eriksen HR. Low back pain interventions at the workplace: a systematic literature

review. Occup Med (Lond) 2004;54(1):3-13.

Ukoumunne OC, Thompson SG. Analysis of cluster randomized trials with repeated cross-sectional binary

measurements. Statistics in medicine 2001;20(3):417-433.

Vahtera J, Kivimäki M, Liira J. The increasing trend in sickness absence among municipality workers is

declining (in Finnish). 2008. Available from

http://www.ttl.fi/Internet/Suomi/Organisaatio/Osaamiskeskukset/Tyoyhteisot+ja+organisaatiot/Sair

auspoissaolojen+kasvu (accessed 20 July 2010).

van den Hoven LH, Gorter KJ, Picavet HS. Measuring musculoskeletal pain by questionnaires: The manikin

versus written questions. Eur J Pain 2009.

van der Klink JJ, Blonk RW, Schene AH, van Dijk FJ. The benefits of interventions for work-related stress.

Am J Public Health 2001;91(2):270-276.

van der Molen HF, Sluiter JK, Hulshof CT, Vink P, Frings-Dresen MH. Effectiveness of measures and

implementation strategies in reducing physical work demands due to manual handling at work.

Scand J Work Environ Health 2005a;31 Suppl 2:75-87.

van der Molen HF, Sluiter JK, Hulshof CT, Vink P, van Duivenbooden C, Holman R, Frings-Dresen MH.

Implementation of participatory ergonomics intervention in construction companies. Scand J Work

Environ Health 2005b;31(3):191-204.

van der Windt DA, Thomas E, Pope DP, de Winter AF, Macfarlane GJ, Bouter LM, Silman AJ.

Occupational risk factors for shoulder pain: a systematic review. Occup Environ Med

2000;57(7):433-442.

van Eerd D, Cole D, Irvin E, Mahood Q, Keown K, Theberge N, Village J, St-Vincent M, Cullen K,

Widdrington H. Report on process and implementation of participatory ergonomic interventions: a

systematic review, volume 1. Toronto: Institute for Work and Health,

2008.http://www.iwh.on.ca/sys-reviews/implementation-of-pe-interventions (accessed 10

September 2010).

125

van Poppel MN, Hooftman WE, Koes BW. An update of a systematic review of controlled clinical trials on

the primary prevention of back pain at the workplace. Occup Med (Lond) 2004;54(5):345-352.

van Poppel MN, Koes BW, Smid T, Bouter LM. A systematic review of controlled clinical trials on the

prevention of back pain in industry. Occup Environ Med 1997;54(12):841-847.

van Rijn RM, Huisstede BM, Koes BW, Burdorf A. Associations between work-related factors and the

carpal tunnel syndrome--a systematic review. Scand J Work Environ Health 2009;35(1):19-36.

van Tulder M, Furlan A, Bombardier C, Bouter L. Updated method guidelines for systematic reviews in the

cochrane collaboration back review group. Spine (Phila Pa 1976) 2003;28(12):1290-1299.

Verhagen AP, de Vet HC, de Bie RA, Kessels AG, Boers M, Bouter LM, Knipschild PG. The Delphi list: a

criteria list for quality assessment of randomized clinical trials for conducting systematic reviews

developed by Delphi consensus. J Clin Epidemiol 1998;51(12):1235-1241.

Viikari-Juntura E, Rauas S, Martikainen R, Kuosma E, Riihimäki H, Takala EP, Saarenmaa K. Validity of

self-reported physical work load in epidemiologic studies on musculoskeletal disorders. Scand J

Work Environ Health 1996;22(4):251-259.

Viikari-Juntura E, Shiri R, Solovieva S, Karppinen J, Leino-Arjas P, Varonen H, Kalso E, Ukkola O. Risk

factors of atherosclerosis and shoulder pain--is there an association? A systematic review. Eur J

Pain 2008;12(4):412-426.

Virtanen M, Pentti J, Vahtera J, Ferrie JE, Stansfeld SA, Helenius H, Elovainio M, Honkonen T, Terho K,

Oksanen T, Kivimäki M. Overcrowding in hospital wards as a predictor of antidepressant treatment

among hospital staff. Am J Psychiatry 2008;165(11):1482-1486.

Volinn E. Do workplace interventions prevent low-back disorders? If so, why?: a methodologic

commentary. Ergonomics 1999;42(1):258-272.

Walker-Bone K, Cooper C. Hard work never hurt anyone--or did it? A review of occupational associations

with soft tissue musculoskeletal disorders of the neck and upper limb. Ann Rheum Dis

2005;64(8):1112-1117.

Walker-Bone K, Reading I, Coggon D, Cooper C, Palmer KT. The anatomical pattern and determinants of

pain in the neck and upper limbs: an epidemiologic study. Pain 2004;109(1-2):45-51.

Walker-Bone KE, Palmer KT, Reading I, Cooper C. Soft-tissue rheumatic disorders of the neck and upper

limb: prevalence and risk factors. Semin Arthritis Rheum 2003;33(3):185-203.

Wearing SC, Hennig EM, Byrne NM, Steele JR, Hills AP. Musculoskeletal disorders associated with

obesity: a biomechanical perspective. Obes Rev 2006;7(3):239-250.

Weevers HJ, van der Beek AJ, Anema JR, van der Wal G, van Mechelen W. Work-related disease in general

practice: a systematic review. Fam Pract 2005;22(2):197-204.

Westgaard RH, Winkel J. Ergonomic intervention research for improved musculoskeletal health: A critical

review. International Journal of Industrial Ergonomics 1997;20(6):463-500.

WHO. Identification and control of work-related diseases. WHO Technical Report Series 714. Geneva:

World Health Organization, 1985.

Wilson J, Haines H. Participatory ergonomics. In: Salvendy, G, ed. Handbook of human factors and

ergonomics. 2nd edn. New York: Wiley, 1997:490-513.

126

Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, Tugwell P, Campbell SM,

Abeles M, Clark P, et al. The American College of Rheumatology 1990 Criteria for the

Classification of Fibromyalgia. Report of the Multicenter Criteria Committee. Arthritis Rheum

1990;33(2):160-172.

Yeung SS, Genaidy A, Deddens J, Alhemood A, Leung PC. Prevalence of musculoskeletal symptoms in

single and multiple body regions and effects of perceived risk of injury among manual handling

workers. Spine 2002;27(19):2166-2172.

Zubieta JK, Heitzeg MM, Smith YR, Bueller JA, Xu K, Xu Y, Koeppe RA, Stohler CS, Goldman D. COMT

val158met genotype affects mu-opioid neurotransmitter responses to a pain stressor. Science

2003;299(5610):1240-1243.

Zwerling C, Daltroy LH, Fine LJ, Johnston JJ, Melius J, Silverstein BA. Design and conduct of occupational

injury intervention studies: a review of evaluation strategies. Am J Ind Med 1997;32(2):164-179.

Ørhede E. Nordic cooperation in research on the work environment. Scand J Work Environ Health

1994;20(1):65-66.

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