Postural and muscular adaptations to repetitive simulated work

Abstract

Complex repetitive tasks are common in the workplace and have been associated with upper extremity disorders. The purpose of this study was to examine the progressive effects of highly repetitive work on joint kinematics and muscle activity of the trunk and upper extremity. Fifteen healthy men performed 60 one-minute cycles of 4 simulated automotive-related tasks. Electromyography of eight muscles and kinematics of the trunk and right upper extremity were collected. Data were analysed at 12-min intervals and divided into a complete work cycle. The time to complete the work cycle decreased by 6.3 s over the trials. Peak shoulder flexion decreased and peak elbow flexion increased during the work cycle. Muscle activity magnitude and variability was influenced by time during the repetitive tasks. This study found adaptations to highly repetitive but light work in only 1 h; redistributing muscle demands within the shoulder over time may reduce muscle fatigue development.

Practitioner Summary: While the work was not strenuous, we were able to demonstrate muscular and postural adaptations in a single hour of simulated work. By evaluating both the whole work cycle and the sub-tasks, we aim to develop new methods for evaluating the risk of complex tasks in prolonged repetitive work.

Keywords:

• Repetitive movement
• posture
• upper extremity
• surface electromyography

Acknowledgements

The authors would like to thank Jeremy Watkin for his assistance with data analysis.

Additional information

Funding

This study was funded by AUTO21 Network of Centres of Excellence [AE403-AME] and also supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant [217382-09].