Assessing the potential for "undesired" effects of passive back-support exoskeleton use during a simulated manual assembly task: Muscle activity, posture, balance, discomfort, and usability.

Back-support exoskeletons (BSEs) are wearable systems designed to reduce physical demands on the back, but which could have undesired effects beyond this design intention. Participants (n = 18) used two commercial BSEs to complete a brief (~15-20 s) simulated manual assembly task in varying conditions, with outcome measures that included: working posture, activity levels in "secondary" muscle groups (shoulders and thighs), perceived balance, discomfort, and usability. Using a BSE led to small and inconsistent changes in working postures (e.g., < ~14° change in lumbar flexion), muscular activity in the secondary muscle groups (<±2% of maximum voluntary isometric contractions), or perceived balance. Limitations in movement were reported for both BSEs, however, along with moderate levels of discomfort. Task-specific responses were evident for all outcome measures, though these depended on the specific BSE used and differed between genders in many cases. Future work should focus on interactions between a given user, BSE design, and task conditions.