Prevention of MSDs by workload optimization based on external and internal load assessment methods...
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Prevention of MSDs by workload optimization based on external and internal load assessment methods
Danuta Roman-LiuCentral Institute for Labour Protection – National Research Institute
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
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
50
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