Effects of Back-Support Exoskeletons on Balance Recovery From Overground Slips and Trips

Abstract

Back-support exoskeletons (BSEs) are widely used in industry to reduce risk factors for work-related musculoskeletal disorders during manual material handling tasks. They may, however, increase fall risk by adversely affecting balance recovery after slips and trips. Prior work on BSEs and their effects on balance recovery has mainly relied on treadmill or lean-release perturbations to simulate slips and trips, which may elicit different recovery responses than overground slips and trips. This dissertation comprises three studies that investigated the effects of passive BSEs on fall rate and balance recovery after overground slips and trips. The purpose of the first study was to investigate the effects of BSEs on fall rate and balance recovery after lab-induced overground trips. Two commercial passive BSEs with distinct designs were selected: the HeroWear, which has soft elements and elastic bands, and the BackX, which has a rigid frame and mechanical torque generators. Participants were exposed to two overground trips, one with and one without a BSE. The results did not show a difference in fall rate after trips between wearing and not wearing a BSE, or between BackX and HeroWear. However, BSEs elicited changes in balance recovery kinematics, including shorter recovery step time and shorter recovery step length with HeroWear and, when participants used an elevating recovery strategy, greater hip drop with BackX. The purpose of the second study was to investigate the effects of BSEs on fall rate and balance recovery after lab-induced overground slips. Participants were exposed to a single overground slip with or without a BSE. The results did not show a difference in fall rate after slips between wearing and not wearing a BSE, or between BackX and HeroWear. However, BSEs elicited changes in balance recovery kinematics, including smaller peak hip drop with HeroWear and greater slip distance with BackX. The purpose of the third study was to investigate the effects of anterior load carriage and BackX on fall rate and balance recovery after lab-induced overground trips. The results did not show an increase in fall rate after trips with anterior load carriage. However, anterior load carriage elicited changes in balance recovery kinematics, including longer recovery step time, longer recovery step length, greater hip drop in females, and smaller torso flexion angle. Additionally, the results did not show an increase in fall rate after trips with BackX during anterior load carriage. However, BackX elicited changes in balance recovery kinematics, including a shorter recovery step time and smaller hip drop. Taken together, these studies provide insight into how passive BSEs affect balance recovery after overground slips and trips. The findings do not support the concern that these BSEs increase fall rate after slips or trips. However, BSE effects on balance recovery kinematics were device-specific and varied from beneficial to adverse, which can inform BSE use in workplaces where slips and trips are common.