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). The structural bottleneck thought to bring about these changes is older adults have more compliant tendons than young, or a less stiff spring. This leads to operating with shorter less optimal muscle lengths, and necessitates higher muscle activation, 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 is a critical gap in understanding whether beneficial exoskeleton assistance strategies for younger adults will also benefit older adults and if so, what the underlying mechanism is that enables exoskeletons to reduce metabolic cost across age. The near-term objective of my work, is to evaluate the calf muscles and tendon’s role in modifying metabolic cost during walking with (i) passive, and (ii) active ankle exoskeletons across age. My central hypothesis is that ankle exoskeletons can offset age-related changes in physiology to reduce metabolic cost to that of young walking economy.
I will use electromyography to measure muscle activity, B-mode ultrasound to track muscle level changes, and a portable indirect calorimetry system to measure metabolic cost in young and older adults with passive and active exoskeleton conditions. It is anticipated that these Aims will yield a greater understanding of how people interact with ankle exoskeletons to modify metabolic cost. These outcomes are expected to 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. This work will also pave the way for studies in more functional measures such as increasing self-selected walking speed, improving balance, and reducing fatigue that may translate more directly to improved quality of life.