SUMMARY

Difficulties with mobility were the most commonly reported disability for those age 65 and over. It is well known that older adults are slower and less economical during walking compared to young. This is thought to be brought on by reduced ankle push off power and a redistribution of positive power generation to more proximal joints (e.g., hip). Older adults have less stiff springlike tendons than young and operate with shorter less optimal muscle lengths, leading to a loss of the ‘spring in their step’. This necessitates higher muscle activations and reliance on muscles at less efficient joints like the hips, increasing metabolic cost during walking. Ankle exoskeletons have been shown to increase ankle push off, increase self-selected speed, and reduce metabolic cost in young adults for a near immediate improvement in walking performance. There was a critical gap in understanding whether beneficial exoskeleton assistance strategies for young adults will also benefit older adults and if so, what the underlying mechanism is that enables exoskeletons to reduce metabolic cost across age. My central hypothesis was ankle exoskeletons can offset age-related changes in physiology to reduce metabolic cost to that of young walking economy. I measured muscle activity (electromyography), muscle level changes (B-mode ultrasound), and metabolic cost (indirect calorimetry) in young and older adults with passive and active exoskeleton assistance. These aims yielded a greater understanding of how people interact with ankle exoskeletons to modify metabolic cost. These outcomes can improve the design and control of ankle exoskeletons to improve the cost of walking across age, leading to greater mobility and increased quality of life. Completion of the aims, paved the way for studies in more functional measures such as increasing walking speed, improving balance, and reducing fatigue that may translate more directly to improved quality of life.