Prevention of MSDs by workload optimization based on external and internal load assessment methods

Danuta Roman-LiuCentral Institute for Labour Protection – National Research Institute

Work incapacity due to MSDs in 2003 - 2005

Work incapacity due to MSDs in relation to all incapacities in 2003 – 2005

Sectors with the highest rate of MSDs (according to Polish National Labour Inspectorate)

• transportation• agriculture, fishing, forestry• mining• building industry,• wholesale and retail trade• hotels and restaurants,• health care

Risk factors for MSDs

Home environment

Leisure time٭Diet٭Sport٭

Work environment

Biomechanical factors ٭ posture force time sequencesPsychosocial factors ٭ job demands control social support

Individual characteristics

Genetically determined inclination to diseases٭Personality٭Gender٭Age٭Physical capacity٭

External and internal load at the work stand

Internal load is the reaction of musculoskeletal system to the external load.

Methods:

sEMG

ECG

HR

Oxygen consumption

Subjective assessment

External load can be assessed as a function of parameters describing performed task (body parts configuration, exerted force, time).

Methods:

NIOSH

OCRA

OWAS

LIMB

Assessment of muscle load and fatigue using sEMG

Placement of sEMG electrodessEMG registered from four upper limb muscles

Ovako Working Posture Analysis System

Packing stand involving repetitive tasks

Before intervention

After intervention

intervention

Musculoskeletal load assessment on the Bale Opener work stand

Tasks (phases in the cycle) Time of phase (s)

Preparation 45

Cutting ties 60

Removal of ties 45

Walking to the other side of bale 24

Cutting ties 30

Removal of the ties 280

Disposal of ties 20

Walking to the lift 30

Steering the lift 120

Workers at the „Bale Opener” work stand reported pain in wrist and hand.Musculoskeletal load of upper limb was assessed by means of sEMG.

Load level of examined muscles during each of cycle phases

0

10

20

30

40

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60

70

80

90

100

0 20 40 60 80 100

[% MVC]

[% of cycle time]

RMG

0

10

20

30

40

50

60

70

80

0 20 40 60 80 100

[% MVC]

[% of cycle time]

ECR

0

5

10

15

20

25

30

35

40

45

0 20 40 60 80 100

[% MVC]

[% of cycle time]

FCU

ResultsAnalysis of musculoskeletal load of forearm and hand shows that: high musculoskeletal load of hand٭lower, however still high, musculoskeletal load of forearm٭ the highest musculoskeletal load during tasks of cutting ties and this can٭cause upper limb pain an important factor in the development of pain symptoms can be the shape٭of steering device, which is the main cause of musculoskeletal load in phases of steering the lift

♦ Changes of the shape of steering device by having it smaller and lighter with shape fitting the hand and decreasing the push button force.

♦ Reduction of musculoskeletal load during cutting ties can be reached by implementation of scissors with pneumatic, hydraulic or electric aid.

Indicators for ergonomic intervention