Evaluation of Muscle Activity and Usability of an Upper-Limb Exoskeleton in Power Grid Maintenance Tasks

Power grid maintenance tasks often involve sustained arm elevation, asymmetric upper-limb loading, and repetitive pulling, all of which may increase the risk of work-related musculoskeletal disorders. This study evaluated the effects of a passive upper-limb exoskeleton on muscle activity, subjective fatigue, task workload, and usability in three representative power grid maintenance tasks: insulator installation, insulated rod handling, and hand-chain hoist operation. A randomized crossover design was adopted, and twenty-two healthy young male participants completed all tasks under exoskeleton (EXO) and no-exoskeleton (NoEXO) conditions. Surface electromyography was used to quantify muscle activity, and subjective assessments included Borg CR-10, NASA-TLX, an exoskeleton wearing experience questionnaire, and the System Usability Scale (SUS). In the static tasks, the exoskeleton significantly reduced %MVC of the trapezius, deltoid, and biceps brachii, while in the dynamic task, significant reductions were mainly observed in the deltoid and trapezius during the arm-raising phase. The exoskeleton also reduced local discomfort in the shoulders, elbows, and wrists and improved selected workload dimensions, particularly physical demand and effort. The mean SUS score was 74.2, indicating acceptable usability. These findings suggest that the passive upper-limb exoskeleton can effectively reduce proximal upper-limb loading in power grid maintenance tasks, with the greatest benefit observed in static overhead work.