Physiological and perceptual effects of two passive back-support exoskeletons during repetitive lifting in healthy adults

Passive back-support exoskeletons (PBEs) are wearable devices designed to reduce strain during physical labor, e.g., repetitive lifting. This study investigated acute effects of two PBEs on cardiac load, energy expenditure, neuromuscular activity, and perceived exertion during repetitive lifting. Twenty-six healthy adults performed a standardized lifting task under three conditions: without exoskeleton (FREE), with a rigid PBE (RIGID), and with a soft PBE (SOFT). Cardiac load was assessed via impedance cardiography and blood pressure; energy expenditure via respiratory gas analysis; and neuromuscular activity via surface electromyography. Subjective ratings of exertion and comfort were collected before, during, and after the task. Data were analyzed using repeated measures analyses of variances and mixed-effects models, all followed by post-hoc tests. Both exoskeletons reduced rate-pressure product (RIGID: −8.1%, p = 0.001; SOFT: −6.5%, p = 0.003), energy expenditure (RIGID: −13.9%, p < 0.0001; SOFT: −9.4%, p < 0.0001), and perceived exertion (RIGID: −14.4%, p < 0.001; SOFT: −9.5%, p = 0.034) compared to FREE. Only RIGID reduced gluteus maximus muscle activation (− 21%, p = 0.005). No significant changes were observed in trunk or abdominal muscles. Wearing comfort declined post-task for both devices. No differences occurred between PBEs across all parameters. This study demonstrates that rigid and soft PBEs consistently reduce physiological and perceptual demands during lifting. By integrating central and peripheral hemodynamic measures, we extend understanding of cardiac unloading. Long-term field studies are needed to assess whether these benefits persist in real-world settings and contribute to musculoskeletal and cardiovascular health.