Short-Term Adaptations to Lifting and Gait Kinematics When Using a Passive Back-Support Exoskeleton.

Prior work quantifying the biomechanical effects of back-support exoskeleton use has mostly focused on the effects of brief periods of exposures to exoskeletons. Hence, there is currently limited understanding of how movement kinematics may be altered by more prolonged exposures. We assessed the effects of a 75-min exposure to a passive back-support exoskeleton on adaptations to lifting strategies, gait kinematics, and postural stability. Twelve participants performed tasks in an ABA protocol-measurements were obtained before (Pre-EXO phase), during (EXO-adaptation phase), and after exoskeleton-use (Post-EXO phase). A piecewise linear regression model was used to estimate changes to the dependent variables within and between each phase. Trunk range of motion (ROM), peak trunk flexion angle, and flexion velocity showed significant decrease (6-8%) on introduction of the exoskeleton, and significant reversals on doffing the exoskeleton. However, there were no significant adaptation effects (changes during EXO-adaptation phase) to trunk kinematics. For gait, a more cautious gait pattern was observed during exoskeleton-use: step length decreased, step width increased, minimum toe clearance increased, and hip ROM decreased, compared to the baseline Pre-EXO phase. These measures also reversed on doffing the exoskeleton and demonstrated further carry-over effects during the Post-EXO phase. However, no significant adaptations were evident in gait kinematics. Exoskeleton introduction, use, and doffing did not alter the cycle-to-cycle variability of trunk kinematics, or postural stability during static stance and maximum leans. These findings can help guide the practical development of training and use protocols for safe exoskeleton use in occupational settings.