the impact on musculoskeletal disorders of changing physical and psychosocial work environment...

International Journal of Industrial Ergonomics 28 (2001) 31–45

The impact on musculoskeletal disorders of changing physicaland psychosocial work environment conditions in the

automobile industry

K. Fredrikssona,b,*, C. Bildtc, G. Hagga, A. Kilboma

aProgramme for Ergonomics, National Institute for Working Life, SE-112 79 Stockholm, SwedenbDepartment of Physical Therapy, Karolinska Institute, Huddinge, Sweden

cGender and Work, National Institute for Working Life, SE-11279 Stockholm, Sweden

Received 11 July 2000; accepted 10 January 2001

Abstract

In the car-body-sealing department at an automobile assembly plant in Sweden, a reorganisation of work fromlineout to line production was performed. The aim of the present investigation was to study the influence of changes inphysical and psychosocial conditions on musculoskeletal disorders. Working conditions were studied on two occasions,

before and after the change. Physical workload regarding strenuous postures and movements was assessed byquestionnaires, direct measurements recordings and by computer based observations registrations, and the psychosocialconditions by questionnaires and group discussions. The musculoskeletal disorders of the workers were studied by

reports from the occupational health care centre and by self-reported musculoskeletal symptoms. A decrease in the timespent in strenuous positions was found, but the work cycle time decreased considerably and the worker felt ‘robotised’.There was a marked decrease in the perception of opportunities to influence the work, as well as the stimulation atwork. The amount of musculoskeletal disorders increased for the study group, but not for a reference group from the

same plant. A possible explanation for the increase in musculoskeletal disorders was the increase in perceived physicalexertion and the decrease in occupational pride.

Relevance to industry

This paper illustrates the importance of paying attention to psychosocial issues in order to avoid musculoskeletal disorders

after an intervention mainly aimed at physical workstation design. # 2001 Elsevier Science B.V. All rights reserved.

Keywords: Line production; Change process; Physical working conditions; Psychosocial working conditions; Perceived physical

exertion; Occupational pride; Musculoskeletal disorders

1. Introduction

Work-related musculoskeletal disorders consti-tute a major problem in many industrialisedcountries (Hagberg et al., 1995), despite the atten-tion given to ergonomics during recent years

*Corresponding author. Programme for Ergonomics, Na-

tional Institute for Working Life, SE-112 79 Stockholm,

Sweden. Tel.: +46-8-730-93-07; fax: +46-8-730-92-46.

E-mail address: [email protected]

(K. Fredriksson).

0169-8141/01/$ - see front matter # 2001 Elsevier Science B.V. All rights reserved.

PII: S 0 1 6 9 - 8 1 4 1 ( 0 1 ) 0 0 0 1 1 - 7

(Westgaard and Winkel, 1997). A number ofoccupational factors have been identified as beingassociated with musculoskeletal disorders (Putz-Anderson et al., 1997). Regarding upper extremitydisorders, especially repetitive work (Onishi et al.,1976; Rossignol et al., 1987; Chiang et al., 1993;Ekberg et al., 1994; Kilbom, 1994a, b; Ohlssonet al., 1995), work in extreme and static postures(Kilbom et al., 1986; Ohlsson et al., 1995; Punnettet al., 2000) and work including forceful arm andhand movements (Aaras and Stranden, 1988;Veiersted, 1994; Viikari-Juntura et al., 1994) havebeen found to be associated with disorders. Lowback disorders have been found to be associatedwith heavy lifting and forceful movements (Pun-nett et al., 1991), as well as with work in a forward-bent position (Vingard et al., 2000). Short workcycles has been found to increase the risk of handand wrist injury markedly (Silverstein et al., 1986).Also psychosocial conditions in general (Linton,2000), poor social support at work (Bongers et al.,1993), opportunity to influence decisions (Theorellet al., 1991), work pressure (Sauter et al., 1993)and lack of variety and work satisfaction (Hop-kins, 1990) have been found to be associated withmusculoskeletal disorders. Interactive effects be-tween physical and psychosocial work environ-ment factors have been demonstrated (Saari, 1994;Laitinen et al., 1998). Regarding musculoskeletaldisorders, interactive effects from physical andpsychosocial exposures have been found (Fre-driksson et al., 2000; Linton, 1990; Bildt Thorb-jornsson et al., 1999). Studies of associationsbetween work environment factors and musculo-skeletal disorders should preferably include bothphysical and psychosocial sources of information(Johansson et al., 1993).In today’s working life there is an increasing

demand for both organisations and individuals toadjust to changes, both regarding physical andpsychosocial work environment conditions (Ran-tanen, 1999). Only few field studies have beenpublished concerning the effect of changingconditions on musculoskeletal disorders (West-gaard and Winkel, 1997). Reduction in physicalexposure level may be beneficial for musculoske-letal health when the exposure level was highinitially (Aaras, 1994b), but the impact of exposure

reduction was not clear in jobs with low exposurelevels (Aaras, 1994a). By reducing physical riskfactors and increasing workers’ skills, sick-leavedue to low back disorders fell significantly amongworkers in the metal industry (Wickstrom et al.,1993), while no such reduction of disorderscould be seen among Swedish dentists, when newworkstations allowing better working postureswere introduced (Kronlund, 1981; Winkel andWestgaard, 1996).Working organisational conditions may contri-

bute to the amount of musculoskeletal disorders,but in most published studies dealing withorganisational factors, health outcome was notreported (Westgaard and Winkel, 1997). Musculo-skeletal symptoms of upper limbs increased afterthe introduction of flow-lines in fish-fillet plants(Olafsdottir and Rafnsson, 1998). However, nodifference regarding prevalence of musculoskeletalsymptoms was seen when comparing an unpacedtruck-axle assembly line system to a parallelisedsystem with a longer job cycle time (Johanssonet al., 1993).The way in which changes are implemented has

been found to have an important impact on theresults. The success of the interventions studied,also including improved health, was attributed to aparticipatory problem-solving approach (Lifshitzet al., 1991; Moore and Garg, 1994; Riley et al.,1994; Schoenmarklin and Monroe, 1994). In astudy on musculoskeletal symptoms among per-sons in different occupations, persons who per-ceive their psychological workload as high andtheir decision latitude as low reported more neck,shoulder and low back symptoms than personswho reported low psychological workload andhigh decision latitude (Johansson, 1995). If Jo-hansson’s hypothesis is true, a participatoryergonomic process, which provides more decisionlatitude for the workers might be advantageous forthe prevention of musculoskeletal injuries (Laiti-nen et al., 1998). Another application of aparticipatory ergonomic process, where technicalimprovements were chosen as the way to deal alsowith psychosocial problems, was found successfulin terms of reduced absenteeism and improvedpsychosocial and physical work environmentconditions (Laitinen et al., 1998).

K. Fredriksson et al. / International Journal of Industrial Ergonomics 28 (2001) 31–4532

1.1. Background for the present study

In the car-body-sealing department at a largeautomobile assembly plant in Sweden, a reorgani-sation of the work from lineout to line productionwas performed in 1997. The reason for the changewas merely of an economic and productive nature,but ergonomic considerations were also taken intoaccount. Better opportunities to provide individu-ally adjusted workstations, increased work contentand more variety in the work tasks were goals setup by the management. It was also decided toevaluate the intervention from an ergonomic pointof view. The implementation of the new produc-tion line was intended to involve the operators, inorder to facilitate a smooth implementationprocess. However, there was some apprehensionthat the new line production and the new socialconditions at the workplace would lead to newproblems, presumably also involving musculoske-letal disorders.

1.2. Aims

The aim of the present investigation was tostudy the production system before and after thechange, with respect to change in physicalvariables, psychosocial factors and musculoskele-tal disorders. The hypothesis was that a decrease inphysical exposure, i.e. less time spent in strenuouspositions and less repetitive hand/finger move-ments, together with more variety regarding worktasks, should lead to fewer musculoskeletal dis-orders and reduced sick-leave. The impact of theparticipatory implementation process has beenreported elsewhere (Bildt et al., 2000), but anadditional aim of this study was to evaluateassociations between the implementation processand musculoskeletal disorders.

2. Methods

2.1. Description of the workplace

Before arriving at the car-body-sealing depart-ment the cars were sealed by robots. However,manual sealing was needed for some parts of the

cars, e.g. around doors and inside the cars, due tohigh quality demands. Application of sealingcompound was carried out with a spray gun.Some robot sealing and the manually appliedcompound had to be smoothed out with a brush.Other equipment, such as plugs and carpets, weremounted on the car bodies in this department. Thecar-body-sealing task demanded a high level ofcraftsmanship, requiring a six-month trainingperiod to become a fully competent operator.However, the long learning time was consideredan obstacle for engaging new employees. The em-ployer wanted to be able to use the new co-workersfaster. This was also one of the company’sreorganisation goals, along with aims such as lesssick-leave, better quality of the sealing work,increase in number of cars sealed and bettercontrol over the order flow of cars through theplant. For logistic reasons the same order ofbodies had to be kept throughout the wholeproduction process.After the implementation of the new organisa-

tion a new car model was introduced. This newproduct meant that much of the time that wasintended to be used in the implementation processhad to be used for other purposes.

2.1.1. The lineout systemBefore the intervention all cars were sealed in

workstations where a pair of workers carried outall the work on the car. These often formed fixedpairs, usually sealing either the left or the right sideof the car. When a car was ready, a new one wasordered from the line of operators. Each pair ofworkers had a daily quota to fill. The estimated timefor sealing one car was approximately 20min, butdiffered somewhat for different models. Many of theoperators did the sealing work much faster, andaccording to our registrations the mean time forsealing a car was about 15min. This gave theoperators the freedom for example to take longerbreaks or to make telephone calls, etc. It waspossible to adjust the height of the car, but not tomake any individual adjustments of the workplace.

2.1.2. The line systemIn the new system all cars appeared in a fixed

order on a line. The cars were placed on ‘‘palettes’’

K. Fredriksson et al. / International Journal of Industrial Ergonomics 28 (2001) 31–45 33

which moved ahead slowly along the line. Thework was performed on these moving platforms.The ‘‘palettes’’ allowed individually adjustableheights on the sides of cars, but not in front ofor behind them. The height of the car was alsoadjustable, now to a larger extent than before.Along the line the work was divided into work-stations and a worker did certain tasks at everystation, the same on every car. The operatorsworked in teams of 7–8 individuals, and each teamwas responsible for 3–4 workstations. Four times aday the workers changed stations. This meant thatthey performed the same task during two con-secutive hours. The duration of the individualwork tasks was between 15 and 90 s. The operatorscould not leave the line without anyone else to takehis/her place. Even if the line was halted dueto some error, the workers had to remain in theirplaces so as to be able to begin workingimmediately when the line started again.

2.2. Procedure

The first part of the study was performed inMarch and April 1997. During the summer holi-day the new production system (the line system)was installed. The second part of the study wasperformed in March and April 1998, when theworkers had got used to the new situation. Onboth occasions the participants filled in question-naires regarding physical and psychosocialconditions, and concerning musculoskeletal dis-orders. Regarding physical working conditions,direct measurements and computer-based observa-tion registrations were also carried out in Februaryand March 1997 and in March and April 1998,respectively, for some of the operators at the sealingdepartment. The implementation of the change wasfollowed by interviews conducted by psychologistson three different occasions before, during and afterthe intervention. Interviews were conducted with 7 ofthe 10 teams of operators (randomly assigned), andwith five members of the management.

2.3. Study group

Operators from the sealing department filled inquestionnaires before and after the intervention.

At the sealing department, the response rate was87 per cent on the first occasion (78 of 90distributed questionnaires were returned). On thesecond occasion, after the change, 74 per cent ofthose who answered the first questionnaire re-turned a second one. These 57 persons, 33 womenand 24 men, formed the study group. The reasonsfor not returning the second questionnaire werechange of work, absence due to childbirth and insome cases unwillingness to participate. The meanage among the women was 39.1 years (standarddeviation, sd, 8.7 years) and among the men 32.5years (sd 9.6 years). Among the women 90 per centand among the men two thirds had been gainfullyemployed for more than 10 years. More than halfof the women and a quarter of the men hadworked at the sealing department for more than 10years.

2.4. Reference group

The reference group consisted of 45 operators,10 women and 35 men, from another car-bodydepartment at the same plant, dealing with metalcar equipment. The reference group was the groupat the plant that had most similar workingconditions to those of the study group. In thedepartment of the reference group no changes hadtaken place during the time period in question.The low response rate in the reference group(about 50 per cent), made it necessary to use allanswers, irrespective of whether the operators hadanswered on both occasions or not. The mean ageamong the women in the reference group was 34.8years (sd 9.4 years) and among the men 33.5 years(sd 9.3 years). Three quarters of the women andmore than half of the men had been gainfullyemployed for more than 10 years, however none ofthem had worked all these years at the car-bodydepartment.

2.5. Psychosocial working conditions

Five indices regarding psychosocial workingconditions were constructed using the question-naire-based information (Bildt et al., 2000). TheCronbach alpha coefficients were calculated usingthe module PROC CORR ALPHA in the SAS


statistical software (SAS, 1989), and reported inbrackets after each of the psychosocial indices.

A. Occupational pride: Commitment, securityand perceived importance in work. Responsecategories: ‘‘Yes, very much; on the whole; tosome extent; no, not at all’’ (a=0.81).

B. Job demands: Work pace, workload, enoughtime to perform work and conflicting de-mands. Response categories: ‘‘Always; some-times; mostly not; never’’ (a=0.64).

C. Stimulation from work: Opportunities to learnnew things, demand for skill and creativity.Response categories: ‘‘Almost always; some-times; mostly not; seldom’’ (a=0.52).

D. Opportunities to influence work: Monotony,possibilities to decide how to perform workand what to be included in the work.Response categories: ‘‘Almost always; some-times; mostly not; seldom’’ (a=0.42).

E. Social support at work: Atmosphere, solidar-ity and social support among both workmatesand towards superiors. (Johnson and M, 1988)Response categories:’’ Agree totally; agree tosome extent; agree only to a minor extent; donot agree at all’’ (a=0.85).

The values of the indices were calculated byadding the values from the included questions. Thehighest values were ascribed conditions presumednegative, such as low level of commitment towork, high work pace, no opportunities to learnnew things, high monotony and loss of goodatmosphere at work. The index values derivedwere dichotomised at the 75th percentile. Thoseoperators who received values corresponding tothe upper 25th percentile were considered to haveexperienced deleterious conditions regarding theindex in question.

2.6. Physical working conditions

Regarding physical working conditions, ques-tions were asked about time per day spent doingwork above shoulder level, work under knee leveland work in twisted positions, as well as questionsabout precision work and repetitive work with thehands. The operators were also asked to rate theperceived physical workload on a scale from 0 to

14, (the RPE-scale) where 1 represented very, verylight work, 5 fairly light work and 9 hard work(Borg, 1970; Wigaeus Hjelm et al., 1995). The 0–14scale was used instead of the original 6–20 scale,as it was supposed to be more applicable to thework at the automobile assembly plant than theoriginal scale, developed for bicycle ergometertesting situations.The physical workload regarding strenuous

postures and movements was also assessed bydirect measurements using a Physiometer (PHYS)(Aaras and Stranden, 1988) and computer-basedobservation registration (PEOFlex) (Fransson-Hall et al., 1995; Fredriksson et al., 1999b). Workcycle time was measured for the conditions beforeand after the change, using the PEOFlex registra-tions. For the measurements and registrations 20operators, 10 women and 10 men were selectedvoluntarily among experienced subjects who be-lieved that they would remain at the departmentalso after the intervention. Due to the considerableinterference with the ordinary work that themeasurement procedure involved, only 10 of thosepersons were selected for measurement investiga-tion. When the second part of the study wasperformed, four of the selected subjects were notpresent due to childbirth (2), sick-leave (1) andtransfer to another department (1). However, all ofthe 10 selected for direct measurements werepresent on the second occasion. The accumulatedworkload, sealing half a car, was measured (PHYSand PEOFlex, n=10) and an estimation of thetotal workload during a whole week was made,using the results from the PEOFlex (n=16)registrations, both before and after the change.The weekly estimates were obtained by weightingthe measurement data in accordance with produc-tion data over the week. After the change, due tothe new organisational conditions mentionedabove, four PEOFlex registrations for each op-erator had to be made in order to estimateworkload for a whole working week.

2.7. Musculoskeletal disorders

The questionnaires included questions regardingmusculoskeletal disorders (aches, pain or discom-fort), both during the last 12 months and the last


seven days (Kuorinka et al., 1987). As the inter-vention period would be included in the reportsderived from the 12 months after the intervention,it was decided to use the reports regarding the lastseven days.The number of visits to the company health care

centre due to musculoskeletal illness, and the totalamount of sick-leave for both the study group andthe reference group, were collected. These figurescould only be derived for the whole departments towhich the study group (n=116) and the referencegroup (n=52) belonged. The time periods Januaryto June 1997 (before the change) and January toJune 1998 (after the change) were compared.

2.8. Statistical analysis

The information on psychosocial and physicalconditions as well as musculoskeletal disorders,before and after the change, was compared for thestudy group and the control group, respectively.The difference in proportions for conditions beforeand after the change was calculated together with95 per cent confidence intervals, by means of thecomputer program CIA, which is a program forstatistical analysis of differences in proportionsbetween groups (Gardener and Altman, 1989).Differences where the confidence interval did notinclude zero were considered as statisticallysignificant results.In order to study the impact from the organisa-

tional change on musculoskeletal disorders, thestudy group was compared to the reference groupby calculating prevalence odds ratios for musculo-skeletal disorders in different anatomical regionsbefore and after the intervention, respectively. Thiswas done by using the module PROC FREQ inSAS statistical software (SAS, 1989).The association between the different physical

and psychosocial conditions and musculoskeletaldisorders in the neck, shoulders, hand/wrist andlow back after the change was calculated. Thiswas done by means of logistic regression analysis(module PROC LOGISTIC in SAS statisticalsoftware) for the study group (n=57) and themembers of the reference group who answeredthe questionnaires after the change (n=21). Theanalyses were controlled for gender.

The internal loss of data was studied. Differ-ences between subjects answering and not answer-ing the different questions was calculated for thestudy group versus the reference group, and forsubjects reporting or not reporting differentmusculoskeletal disorders, using the Chi squaretest in the module PROC FREQ in the SASstatistical software.The interview material was analysed qualita-

tively, with the aim of describing and interpretingthe information given during the interviews (BildtThorbjornsson et al., 1999).Regarding the measurements (Phys) and ob-

servation registrations (PEOFlex), the differencesbetween the conditions before and after the changewere analysed using the paired t-test (the Excelsoftware) with confidence level of 95 per cent as alimit for statistical significance.

3. Results

Only small differences between subjects answer-ing and not answering the questionnaire data werefound. At baseline, but not at the follow-up,subjects with neck disorders had missed thequestions about time spent working under kneelevel and in twisted positions more often thanhealthy subjects. Regarding the psychosocialitems, no differences regarding internal loss ofdata between groups were found.It was planned that the implementation of the

new work organisation should take place succes-sively in an order that was decided beforehand.However, this was not how it was carried out.Time had been allocated for team meetings, but inpractice there was seldom enough time to meet.Production always had priority. After the changeand after the production start of the new carmodel, there was even less time. As a result of thechange in the production process it was obviousthat there was a need for more operators. Anumber of new persons were recruited, but therewas very little time to train them. The newoperators just learned the work at a few stations,and therefore job rotation was even harder tocarry out.


The supervisors appreciated the new productionsystem. A higher level of quality in the sealing (98per cent of the cars without complaint from theline system, as opposed to 94 per cent from thelineout system) and increased productivity (about22 per cent) were results which appeared afterevaluating the intervention 9 months afterwards.

3.1. Workplace conditions before and after thechange

3.1.1. Physical itemsThe work at the department of the reference

group at baseline differed from that at the sealingdepartment in some respects. Fewer operators inthe reference group than in the study groupconsidered that their job involved more than45min work above shoulder level or repetitivework with the hands per day.Among the study group the perceived physical

exertion increased from an average of 6.9 (on ascale of 0–14) before the change, to 8.4 after thechange. Statistically more subjects rated theirphysical workload to be 9 or higher after thechange, while only minor changes regarding other

questionnaire based information on the physicalworkload was found (Fig. 1). Among the referencegroup the perceived physical exertion increasedfrom an average of 6.7 to 7.3 during the timeperiod in question. No statistically significantchanges in the physical workload were identifiedin the reference group.The PEOFlex registrations regarding total

workload during a whole week showed a statisti-cally significant decrease in the time spent in aforward-bent position with the head and trunk,and doing repetitive work with the hands (Fig. 2).However, none of the differences measured by thePhysiometer reached statistical significance. Theduration of work cycles had decreased from about15min to 15–90 s, if sealing half a car wasconsidered as one work cycle before the change.The work was more evenly distributed over theday in the new line system.

3.1.2. Psychosocial conditionsAt baseline 66 per cent of the operators in the

reference group and 35 per cent in the study groupconsidered that their work involved little stimula-tion. In the reference group 29 per cent and in the

Fig. 1. Proportion of operators from the study group, 33 women and 24 men, reporting physical working conditions (performed

>45min/day for all items, except perceived exertion which refers to a whole working day) before and after a change from a lineout

system to a line system. * Statistically significant change, p50.05.


study group 52 per cent reported that their job wasdemanding.After the change a marked decrease regarding

the opportunity to influence their work, and thedegree of stimulation they considered the work tohave, was seen for the study group (Fig. 3). For thereference group their sense of craftsmanshipincreased, but their opportunities to influence theirwork decreased during the same time period.

3.1.3. Musculoskeletal disordersThe study group visited the health care centre

significantly more than the reference group bothbefore and after the change. The number of visitsto the occupational health care centre due tomusculoskeletal illness was 0.3 per worker for thestudy group before the change and 0.4 after.Corresponding figures were 0.02 before and 0.15after the change for the reference group.The questionnaire-based information about

musculoskeletal disorders during the last 7 daysshowed a significant increase in disorders amongthe study group, regarding the upper part of thebody but not regarding the low back and lower

extremity (Fig. 4). No such increase was seenamong the reference group.The prevalence of neck, shoulders, hand/wrist

and the low back disorders increased for the studygroup compared to the reference group, after theintervention (Table 1), but statistically significantresults were only derived regarding low backdisorders. High perceived work load and a reducedoccupational pride were the items which wereassociated with the increase in disorders afterthe intervention (Table 2). Regarding hand/wristdisorders in 1998, no statistically significantassociations were found regarding the physical orpsychosocial items studied.

3.1.4. Other health aspectsThe rate of sick-leave was 14.3 days per worker

for the department of the study group and 5.9 forthe department of the reference group duringthe 6-month period before the change. After thechange the rate of sick-leave was 15.8 days perworker for the department of the study group, and6.8 for the reference group department. Amongother corresponding groups in Sweden this in-crease was similar during the same time period

Fig. 2. Results from PEOFlex recordings before and after a change from a lineout system to a line system among 8 women and 8 men.

Averaged values for a full working week regarding percent of time spent in different postures and performing work. * Statistically

significant change, p50.05.


Fig. 3. Proportion of operators from the study group, 33 women and 24 men, reporting adverse psychosocial working conditions

Fig. 4. Proportion of operators from the study group, 33 women and 24 men, reporting musculoskeletal disorders during the last 7

days before and after a change from a lineout system to a line system. * Statistically significant change, p50.05.


(about 13 per cent), according to figures from theSwedish Employer Association.

4. Discussion

The intervention resulted in improved physicalconditions regarding some aspects, but the per-ceived physical exertion increased. After theintervention musculoskeletal disorders increasedfor the study group but not for a reference groupat the same plant. Loss of occupational pride andthe increased physical exertion were identified asbeing associated with the increase in musculoske-letal disorders for the study group.

4.1. Different probable explanations for theincrease in musculoskeletal disorders

(A) It has been suggested that RPE-ratingsmirror not only physical activity, but also theindividual’s psychological load (Josephson et al.,1996). A perceived high workload has been foundto be associated with seeking care for low backpain (Josephson et al., 1998). In the present studythe operators perceived an increase in physicalexertion, in spite of a decreased amount of timespent in work with bent neck and back, as well asin time spent working with repetitive hand andfinger movements. Ergonomic recommendationsoften include advice to spread the work evenlyover the working day, instead of working hard forpart of the time in order to be able to take longerbreaks. Also regarding this issue the interventioncould be considered as an improvement. However,it did not result in any decrease in the perceivedexertion, rather the contrary. It has been foundthat machine-paced work tasks are more stressfulthan non-paced tasks (Salvendy and Smith, 1981).Fast movements, found to be associated with painin the neck and shoulder region (Bjelle et al., 1981)and the low back (Marras et al., 1995), could be asource of explanation for the increased exertion.No measurements regarding velocity were made,and only a slightly increased number of personsconsidered that they more often had to work fasterafter the change than before. It could, however, behypothesised that working on a line, without beingable to influence the speed, would induce a higherwork pace on the individual tasks, in spite of themeasured more even distribution of work tasksover the day. Increased musculoskeletal symptomsof the upper limbs were seen after the introductionof the flow-line in fish-fillet plants (Olafsdottir andRafnsson, 1998). In the same way as for theworkers in the present study, the change at thefish-fillet plant meant that tasks were demarcatedand simplified.(B) The decrease in work cycle time might be

another explanation. Short work cycles (530 s) orspending more than 50 per cent of the working dayrepeating the same movements has been found toincrease the risk of hand and wrist injury markedly(Silverstein et al., 1986). Regarding neck and

Table 1

Odds ratio (OR), controlled for gender, and 95% confidence

intervals for symptoms in different anatomical regions during

the last 7 days, comparing workers exposed to changed working

organisation conditions (n=57) and workers not exposed to

any such change (n=45); before the change (1997) and after

(1998)

Anatomical regions 1997 1998

OR 95% CI OR 95% CI

Neck 3.0 0.3–35.4 3.0 0.8–12.1

Shoulders 1.1 0.2–6.2 3.9 0.8–18.6

Hand/wrist 0.2 0.02–3.0 2.6 0.6–12.0

Low back 2.2 0.6–9.0 7.2 1.5–35.1

Hips 2.4 0.3–23.1 1.5 0.1–20.8

Knees 3.2 0.8–13.2 1.1 0.2–4.7

Feet 4.9 0.5–46.4 4.9 0.6–41.1

Table 2

Associations between different questionnaire-based physical

and psychosocial working conditions and musculoskeletal

disorders in different anatomical regions during the last 7 days

among 78 operators working at an automobile assembly plant.

Odds ratios (OR) and 95% confidence intervals (CI), controlled

for gender

Anatomical regions

Neck Shoulders Low back

OR 95% CI OR 95% CI OR 95% CI

High perceived

physical exertion

5.6 1.8–21.2 4.9 1.4–20.4 6.4 2.0–24.4

Low occupational

pride

1.8 0.6–6.0 4.6 1.3–18.6 3.6 1.1–12.8


shoulders the association between disorders andshort work cycle time is not so clear, even if alsofor that part of the body increased risks could befound (Silverstein et al., 1986).(C) Another explanation might be related to the

high level of adverse physical postures in the studygroup. More than 85 per cent of the operatorsanswered in the questionnaire that they workedabove shoulder level and with repetitive handmovements for more than 45min a day, bothbefore and after the intervention. Physiometermeasurements and PEOFlex registrations verifythis. Both work above shoulder level and repetitivework with the hands are well-known risk factorsfor upper limb disorders (Onishi et al., 1976;Hagberg and Wegman, 1987; Linton, 1990;Winkel and Westgaard, 1992; Sommerich et al.,1993; Kilbom, 1994b; Fredriksson et al., 2000;Punnett et al., 2000). The amount of work aboveshoulder level, but not work in a forward-bentposition, was much higher among the operators atthe sealing department than in a general popula-tion (Wiktorin et al., 1999). Due to these facts, thework at the sealing department can be consideredas physically hard regarding the upper limb, bothbefore and after the change. Many of theoperators had also been working for a long timeat the sealing department and the disorders mightbe a result of many years of exposure (Andersenand Gaardboe, 1993), in spite of a recent moderatedecrease. A multi-factor model (Rothman, 1986),saying that different exposures together, but notthe single exposures alone, may cause sickness, hasbeen found relevant regarding neck/shoulder pain(Linton, 1990; Brulin et al., 1998; Fredrikssonet al., 2000; Punnett, 1998), hand/wrist tendinitis(Putz-Anderson et al., 1997) and low back pro-blems (Bildt Thorbjornsson et al., 1998, 1999). Itcould be that the operators, who had been workingunder strenuous physical conditions for a longtime, learnt that their hopes for better conditionsand more participation in the change process weredashed. They experienced deteriorated psychoso-cial conditions, musculoskeletal disorders in-creased.(D) Loss of occupational pride was associated

with disorders of the shoulders and low back in thepresent study. The increased work content and

rotation between different work tasks, which wasplanned, was not carried out. The operators spentmost time on the line doing the tasks allocated tothe team, but no longer performed all the differentsealing tasks on the cars. This was considered adecrease in the level of craftsmanship among someof the operators. Other psychosocial items such aslack of stimulation and variation in work tasksand low job discretion (Ekberg et al., 1994),influence over work conditions, few opportunitiesfor development and poor social relations at workhave been found to be associated with musculo-skeletal disorders in other studies (Fredrikssonet al., 2000; Toomingas et al., 1997; Bongers et al.,1993; Ekberg et al., 1994; Bildt Thorbjornssonet al., 1999). In the present study a significantdecrease for the study group in opportunities toinfluence work and in stimulation from work wasalso found after the change, but our analysisshowed no associations between that decrease andmusculoskeletal disorders.(E) The poorly conducted implementation of the

new organisation (Bildt et al., 2001) is anotherprobable explanation for the increase in muscu-loskeletal disorders. It has been suggested that aparticipatory ergonomics process provides theworkers with more decision latitude and mighttherefore be beneficial for prevention of muscu-loskeletal injuries (Johansson, 1995; Laitinenet al., 1998). In the present study the lack offulfilment of the goals of broad participation andimplementation in a previously decided order ofsteps influenced the operators very negatively.After the change, when the operators experiencedthat the management did not take their experienceand willingness to participate in the process ofmaking the new production system work opti-mally, their feelings of disappointment and dis-satisfaction increased even more. More studies areneeded before it is possible to formulate ahypothesis regarding associations between deterio-rated decision latitude conditions and lack ofparticipation in the intervention process, and anincrease in musculoskeletal disorders.(F) In the lineout organisation the operators

had some freedom concerning how to performthe work. In a limited way the sealing work couldbe given a personal touch. In the new line


organisation they expressed that they felt‘robotised’. The only question in the questionnaireused which could mirror ‘creativity’, is one aboutfrequency of using ingenuity at work. The numberof persons who considered that they almost alwayshad to use their ingenuity decreased, while thenumber of persons seldom using their ingenuityincreased after the intervention, but not in astatistically significant way. One hypothesis is thatthe loss of this creativity, however limited, was oneof the reasons for the worsened psychosocialconditions and/or the increase in musculoskeletaldisorders. Another possibility is that the balance inwork (Smith and Sainfort, 1989) had failed, whenthe amount of routine work had increased at theexpense of personal creativity in work, increasingthe level of worker stress.The low response rate in the reference group

may hamper the results in the present study. It isnot possible to conclude which of the above-mentioned theories is the most likely. Differentpersons might be sensitive to different conditions,and it is most likely that not single factors butcombinations of factors are the main reason forthe increase in musculoskeletal disorders.

4.2. Gender differences

Most studies report more musculoskeletal dis-orders among women than among men (StatisticsSweden, 1994; Linton et al., 1998; Fredrikssonet al., 1999a). The only statistically significantgender difference in the present study was regard-ing neck disorders before the intervention. At thesealing department both women and men mostlyhad the same work tasks. More women than men,however, perceived a high physical exertion in theold lineout production. This could partly beexplained by the difficulties in adjusting the oldworkplace individually.

4.3. Data quality

Questionnaire-based information is easy andcheap to collect, but the quality of the informationobtained must be investigated. For physicalconditions in the present study both directmeasurements on the human body, computerised

on-line registrations from observations and ques-tionnaire-based information were obtained. Theanswers regarding these physical conditions couldtherefore be validated, and it was found that theoperators were able to tell the direction of thechange in workload. Regarding some items theywere also able to tell about the magnitude ofexposure and also the magnitude of change. Thepsychosocial conditions were difficult to impossi-ble to validate. The fact that the answers regardingmost physical and psychosocial conditions did notgo in the same direction, in spite of deterioratedmusculoskeletal health, indicates that the resultsare not heavily biased by the disappointmentamong the operators. Our study exemplifies thatquestionnaires can be used when estimating resultsof workplace changes.Many analyses have been performed and there

may be a risk that some of the results can beexplained by chance associations alone (multiplecomparisons effect). The main argument againstthis is that most results are biological plausible,have consistent patterns and that the factorsanalysed have been identified as associated withmusculoskeletal disorders in earlier studies.

4.4. Concluding remarks

In the short run the change from a lineout workorganisation to a line organisation was a successfor the employer. Increased productivity, betterquality and reduced learning time was obtained.The sick-leave rate was not lowered as intended,but the increase was comparable with that of thereference group and other corresponding groups inSweden. However, there might be a risk ofincreased sick-leave for the operators in the sealingdepartment in the future, if no efforts are made toimprove the adverse conditions. There might alsobe a certain risk that the ergonomic problems leadto quality deterioration in the future (Eklund,1995). The introduction of the new car modelmeant both stress due to unaccustomed tasks,equal for the study group and the reference group,and that less time than intended was used forimplementation purposes for the study group. It isunlikely that the results in this study about impact


from reduced professional pride were biased by theimplementation of the new model. New modelshad been introduced before, and the commentfrom the operators was that such a situation waschallenging and stimulating, even if it meantunaccustomed and time-consuming work tasks.

4.4.1. ConclusionsFor the operators the new work organisation

meant reduced stimulation from work, as well asless opportunity to influence their work and alsoincreased musculoskeletal disorders. Working in agroup instead of in fixed pairs was one of the fewpositive outcomes for the operators of the neworganisation. The fact that it was possible toindividually adjust the workstation was appre-ciated, but during the time of the study it did notlead to reduced perceived exertion or a reductionin musculoskeletal disorders. From this study itcould be concluded that it is of utmost importanceto pay attention to psychosocial conditions when achange in the workplace is planned. It could alsobe concluded that a poorly conducted implemen-tation of a new organisation and loss of occupa-tional pride might result in an increase inmusculoskeletal disorders.

Acknowledgements

We are most grateful to the staff at the HealthCare Centre for all their work concerning theevaluation of the reorganisation. In particular wewould like to thank Ann Carlander, StephenStroud and Ulla Pettersson.

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