Arm Differences in Muscle Activity Characteristics During a Bilateral Simulated Overhead Work in Right-Handed and Ambidextrous Individuals

Occupational ApplicationsIn this study, healthy adults performed repetitive bilateral overhead shoulder flexion to fatigue-failure while we measured electromyography of shoulder muscles. We found that ambidextrous and right-handed individuals, especially females, exhibit asymmetrical muscle activation patterns during the task. To enhance worker health and safety, handedness and sex should be considered when implementing workplace changes. For instance, our results may imply that job rotation strategies that alternate use of hands would be easier to implement for males. Moreover, to minimize risk of injury, bilateral asymmetry in muscle activity could be monitored using wearable technology. In our experiment, the mean time to fatigue-failure was under 5 min, which was enough to elicit asymmetry of muscle activation. Therefore, we recommend frequent breaks after a few minutes of work when feasible, in order to avoid asymmetrical loadings during bilateral manual work, especially among females, who both have higher injury risk and more bilateral asymmetry.