How Adaptive Ankle Exoskeleton Assistance Affects Stability During Perturbed and Unperturbed Walking in the Elderly

Slowing the decline in walking mobility in the elderly is critical for maintaining the quality of life. Wearable assistive devices may 1 day facilitate mobility in older adults; however, we need to ensure that such devices do not impair stability in this population that is predisposed to fall-related injuries. This study sought to quantify the effects of untethered ankle exoskeleton assistance on measures of stability, whole-body dynamics, and strategies to maintain balance during normal and perturbed walking in older adults. Eight healthy participants (69-84 years) completed a treadmill-based walking protocol that included perturbations from unexpected belt accelerations while participants walked with and without ankle exoskeleton assistance. Exoskeleton assistance increased frontal plane range of angular momentum (8-14%, p ≤ 0.007), step width (18-34%, p ≤ 0.006), and ankle co-contraction (21-29%, p ≤ 0.039), and decreased biological ankle moment (16-27%, p ≤ 0.001) during unperturbed and perturbed walking; it did not affect the anteroposterior margin-of-stability, step length, trunk variability, or soleus activity during unperturbed and perturbed walking. Our finding that ankle exoskeleton assistance did not affect the anteroposterior margin-of-stability supports additional investigation of assistive exoskeletons for walking assistance in the elderly.