The Association Between Foot–Ankle Mechanical Leverage and Instability During Walking in Older and Younger Adults

Falls in older adults are a serious public health concern with physical and economic consequences that reduce independence and quality of life. Older adults have morphological changes at the foot and ankle that may disrupt foot neuromechanics and the foot's ability to regulate mechanical leverage and balance during walking. This study quantified age and walking speed effects on mechanical leverage of the foot and ankle, as well as the extent to which interindividual differences in foot-ankle leverage correlated with whole-body balance metrics-the latter during habitual walking and in response to 2 contexts of walking balance perturbations. We found no age effect on peak external moment arms due to ground reaction forces. However, older adults exhibited smaller peak ankle moments, larger ranges of frontal plane whole-body angular momentum, larger anterior-posterior margin of stability, and larger perturbation-induced changes in whole-body angular momentum than younger adults. We also report the first evidence that better foot-ankle leverage during habitual walking correlated with larger margins of stability and smaller ranges of whole-body angular momentum. This study was a first step in understanding the relationship between foot-ankle mechanical leverage and whole-body balance.