Mitigating Muscle Fatigue in Upper-Limb Prosthesis Users Through Exoskeletal Weight Compensation

Prosthesis users often experience muscle fatigue and reduced control due to the weight of the device, contributing to high abandonment rates. This study investigates the effects of integrating a soft exoskeleton with a myoelectric prosthesis on upper-limb muscle fatigue and user experience. Nine non-disabled participants performed four functional tasks: drinking from a cup, using a Fork, lifting a box, and reaching overhead, using the prosthesis alone and in combination with the exoskeleton. Muscle activity was recorded via surface electromyography, and perceived exertion was measured using the Borg scale. Kinematics and workload were also assessed through motion capture and the NASA-TLX questionnaire. Usability was evaluated using the System Usability Scale (SUS). Results showed that exoskeleton assistance significantly reduced muscle activation, particularly in the Deltoid, Biceps, and Triceps Lateral Head during the Lift task, with RMS reductions up to 64 % and large effect sizes. Perceived exertion slopes decreased across all tasks, with some instances showing stabilization or reduction during activity. Kinematic analysis indicated minimal impact on shoulder range of motion, with slight adjustments in internal/external rotation remaining within physiological norms. NASA-TLX scores suggested reduced physical demand and effort, and SUS responses indicated moderate usability with room for improvement. These findings demonstrate that soft exoskeletons can effectively unload muscles and reduce fatigue during prosthesis use, highlighting their potential to enhance endurance, task performance, and user comfort. Future work should extend assistance to additional joints and evaluate the system with upper-limb amputees in real-world scenarios.