Muscle loading in exoskeletal orthotic use in an activity of daily living.

Strokes are the leading cause of major adult disability with up to 85% of U.S. survivors experiencing hemiparesis. Physical characteristics of upper-extremity exoskeletal orthotics, used in stroke rehabilitation, were evaluated in terms of performance of activities of daily living (ADL), perceived exertion, and muscle load. Simulated orthotic weight distributions, with total extremity loads of 0.81 kg, 1.25 kg and 2.27 kg, were evaluated along with a 0 kg control condition. Response measures included average shoulder/elbow muscle surface electromyography (sEMG) signal amplitude, quality of task completion and total rest time during performance, and Borg CR-10 scale ratings. Device weight distribution, or imposed shoulder moment, was found to have a significant effect on biceps brachii and anterior deltoid activation levels, percent task completion, total rest time, and perceived exertion ratings. Results suggest that heavier upper-extremity orthotics could cause undesirable effects in terms of muscle loading, performance and exertion; such adverse effects could potentially lead to lack of use during patient's rehabilitation.