The development of an innovative occupational passive upper extremity exoskeleton and an investigation of its effects on muscles

Abstract

Work-related musculoskeletal disorders are one of the main problems reducing the life quality of workers. Occupational exoskeletons are one of the most promising solutions for solving this issue. In this study, an innovative and passive upper-extremity exoskeleton design was presented and tested by measuring ten different muscle activities for two tasks: Task 1, for over-the-head tool handling, and Task 2, for completely stretched forearm tool handling. The special optimized switch mechanism design allowed for free motion when it was not active, which provided design advantages in comparison to the currently available designs. The muscle activity levels were measured via EMG for both tasks and the results were compared and evaluated with and without the exoskeleton on the human body. It was shown that the muscle activity for Task 1 was reduced by 55% for the middle deltoid, 37% for the posterior deltoid, and 27% for the anterior deltoid muscles, in comparison to no exoskeleton for Task 1. For Task 2, the muscle activity was reduced by 48% for the middle deltoid, 20% for the posterior deltoid, and 38% for the anterior deltoid. The exoskeleton presented in this study is an efficient design that significantly increases shoulder comfort, especially in working conditions, without bringing an additional metabolic cost for the secondary muscles.