Mechanical Leverage of the Foot and Ankle: Aging, Balance and the Future of Super Shoes

Older adults utilize their foot and ankle differently compared to their younger adult counterparts during functional activities such as walking. This difference could be a key factor contributing not only to mobility decline but also to a greater falls risk in our rapidly aging population. As fall rates continue to rise in older adults, better understanding of the morphological changes to the foot with age and the role of the foot and ankle in mitigating falls risk is needed. Requisite foot stiffness and the mechanical leverage it conveys play a critical first line of defense in the successful deployment of neuromuscular strategies to mitigate instability during walking and thereby an unexplored but promising target for low-cost, scalable, and widespread intervention. The goal of this dissertation work is to improve our understanding of age-related differences in the neuromechanical interactions between the foot and ankle and how altering mechanical leverage in the aging foot affects older adults’ ability to respond to greater task demands or instability.The first study found that the dynamic mean ankle moment arm captured task demand changes in foot-ankle control during walking, independent of age, suggesting its potential as a control parameter for assistive devices throughout the lifespan. The second study quantified foot-ankle mechanical transmission, revealing that older adults have a reduced transmission capacity, which may impair effective push-off power during walking. The third study showed that older adults exhibit diminished foot-ankle mechanical leverage, and that better leverage associates with greater stability across age groups, highlighting opportunities for assistive interventions. The fourth study demonstrated that carbon fiber insoles improve foot-ankle mechanical leverage and mitigate instability during habitual walking regardless of age. Collectively, these findings provide pivotal insight into neuromechanics of the foot and ankle with the effect of age, and how some of those age-related deficits may be impacted by the use of a low-cost and clinically feasible solution to mitigate fall risk.