The size of cycle-to-cycle variability in biomechanical exposure among butchers performing a standardised cutting task.
The effects of employment duration and pain development on motor variability were investigated during repetitive work. Electromyographic (EMG) and kinematics data from two previous studies were re-analysed. Newly employed butchers were followed prospectively in relation to employment duration and pain development. Healthy butchers with long-term experience were compared with novices. The variability of the cycle time, EMG ratio and arm and trunk movement was expressed as cycle-to-cycle standard deviations. During the first 6 months of employment, cycle time variability decreased, while posture and movement variability increased (p < 0.05). In presence of pain, the variability of the initial arm position decreased while it increased for the trunk (p < 0.05). Experienced butchers showed a larger variability than novices for work cycle and several kinematic variables, but a smaller EMG ratio variability (p < 0.05). These findings indicate that the variability of motor patterns in repetitive work changes with experience and pain. A change towards a more variable motor strategy may protect workers from work-related musculoskeletal disorders.
Laboratory for Work-related Pain and Biomechanics, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. pm@hst.aau.dk
Pascal
P
Madeleine
Michael
M
Voigt
Svend Erik
SE
Mathiassen
D000328:Adult; D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016272:Occupational Health; D013647:Task Performance and Analysis; D013997:Time Factors