Effects of Two Passive Back-Support Exoskeletons on Muscle Activity, Energy Expenditure, and Subjective Assessments During Repetitive Lifting

Abstract

Objective: The aim of this study was to explore the efficacy of two different passive back-support exoskeleton (BSE) designs during repetitive lifting in different postures.

Background: Although BSEs have been proposed as a potential intervention for reducing physical demands, limited information is available about the impacts of different exoskeleton designs in diverse work scenarios.

Method: Eighteen participants (gender-balanced) performed lab-based simulations of repetitive lifting tasks. These tasks were performed in 12 different conditions, involving two BSEs and a control condition, two levels of lifting symmetry (symmetric and asymmetric), and two postures (standing and kneeling). Outcome measures described muscle activity and energy expenditure, along with perceived discomfort, balance, and usability.

Results: Using both BSEs significantly reduced peak activity of the trunk extensor muscles (by ~10%-28%) and energy expenditure (by ~4%-13%) in all conditions tested. Such reductions, though, were task dependent and differed between the two BSEs. In most of the tested conditions, using BSEs positively affected subjective responses regarding perceived exertion and usability.

Conclusion: Our results suggest that the beneficial effects of a BSE are task specific and depend on the specific BSE design approach. More work is needed, though, to better characterize this task specificity and to determine the generalizability of BSE effects on objective and subjective outcomes for a wider range of conditions and users.

Application: Our results provide new evidence to guide the selection and application of passive BSE designs in diverse lifting tasks.

Keywords: asymmetric lifting; electromyography; exoskeleton usability; metabolic demand; wearable technology.