Effects of passive upper-extremity exoskeleton use on motor performance

This study investigated the effect of passive exoskeleton use on shoulder torque control in an intermittent shoulder-loading task. Sixteen participants completed 15 30-sec cycles of intermittent, isometric shoulder contraction at 90º both in the sagittal and scapular planes, with a 50% duty cycle at 30% of maximum torque; this was completed with and without external support from two exoskeletons. Torque steadiness was quantified using the coefficient of variation (CV) across work cycles. Repeated measures ANOVA was used to assess the effects of device support and time on torque CV, with user strength added as a covariate. Exoskeleton use significantly decreased torque CV in both the sagittal and scapular planes. While previous studies have shown exoskeleton-use to reduce musculoskeletal loads, our results show that exoskeleton-use may also improve motor performance by having a steadying effect on shoulder torque generation.