The Influence of Load Handling Height on Shoulder Biomechanics during Sudden Loading

Abstract

Shoulder disorders have been reported as the most severe musculoskeletal disorders among all body parts. Multiple occupational risk factors such as manual material handling, repetitive motion, overexertion, fatigue, and overhead tasks have been reported to be associated with the development of shoulder disorders. The objective of this study was to investigate the effect of height (low, middle, high) on shoulder muscles during sudden loading. Kinematics and Electromyography (EMG) was recorded from 14 male participants. Effect of height found to be significant on normalized EMG and load travel distance. Bilateral shoulder muscles indicated higher NEMG with the increase of the load’s altitude. This increase of muscle activity could have resulted from the greater potential energy of the load at higher altitudes which required extra muscle activity to maintain the biomechanical stability of the shoulder. Reduced stability of shoulder at higher altitudes caused proprioceptive deficit which resulted in higher load travel distance.