Feasibility evaluation of a dual-mode ankle exoskeleton to assist and restore community ambulation in older adults

Background Age-related deficits in plantar flexor muscle function during the push-off phase of walking likely contribute to the decline in mobility that affects many older adults. New mobility aids and/or functional training interventions may help slow or prevent ambulatory decline in the elderly.Objective The overarching objective of this study was to explore the feasibility of using an untethered, dual-mode ankle exoskeleton as a mobility aid to reduce energy consumption, and as a resistive gait training tool to facilitate functional recruitment of the plantar flexor muscles.Methods We recruited six older adults (68-83 years old) to evaluate acute metabolic and neuromuscular adaption to ankle exoskeleton assistance and to evaluate the potential for ankle resistance with biofeedback to facilitate utilization of the ankle plantar flexors. We also conducted a 12-session ankle resistance training protocol with one pilot participant.Results Participants reached the lowest net metabolic power and soleus integrated electromyography (iEMG) at 6.6 ± 1.6 and 5.8 ± 4.9 min, respectively, during the 30-min exoskeleton assistance adaptation trial. Four of five participants exhibited a reduction (up to 19%) in metabolic power during walking with assistance. Resistance increased stance-phase soleus iEMG by 18-186% and stance-phase average positive ankle power by 9-88%. Following ankle resistance gait training, the participant exhibited increased walking speed, endurance, and strength.Conclusions Our results suggest that dual-mode ankle exoskeletons appear highly applicable to treating plantar flexor dysfunction in the elderly, with assistance holding potential as a mobility aid and resistance holding potential as a functional gait training tool.