How Do Exoskeletons Affect Balance During Intermittently Performed Sustained Bending Tasks?

Exoskeletons are beneficial in reducing effort and risk of overexertion-related injury, yet they can also induce side-effects in their wearers. The added weight, as well as interplay of assistive forces of the device can affect wearers' body posture while performing tasks. Factors like fatigue and awkward postures can affect neuromuscular systems, eventually affecting balance. We examined how back-support exoskeletons (BSEs) affect whole-body stability in wearers. Twelve participants performed multiple trials of intermittent wire grasping tasks with 450 trunk flexion, until they reached a medium-high fatigue level with/without BSE in symmetric and with/without 450 (left side) asymmetry. Participants were asked their fatigue level using ratings of perceived exertion (RPE) in back and legs on the Borg CR-10 scale as they stood with one foot on each of two floor-embedded force plates. Findings revealed that both maximum deviation and mean velocity of center of pressure (COP) were ~39% (p-value<0.01) and 133% (p-value<0.05) lower respectively with assistance vs. without in asymmetric posture and remained lower at both low and medium fatigue level in legs. Overall, the difference between ground reaction forces in left vs. right foot was ~28% lower (p-value<0.01) while wearing BSE. Findings from this study may be beneficial in understanding the risk of fall while performing tasks with wearable assistive devices.