Can shank acceleration provide a clinically feasible surrogate for individual limb propulsion during walking?

Aging and many pathologies that affect gait are associated with reduced ankle power output and thus trailing limb propulsion during walking. However, quantifying trailing limb propulsion requires sophisticated measurement equipment at significant expense that fundamentally limits clinical translation for diagnostics or gait rehabilitation. As a component of joint power, our purpose was to determine if shank acceleration estimated via accelerometers during push-off can serve as a clinically feasible surrogate for ankle power output and peak anterior ground reaction forces (GRF) during walking. As hypothesized, we found that young adults modulated walking speed via changes in peak anterior GRF and peak ankle power output that correlated with proportional changes in shank acceleration during push-off, both at the individual subject (R² ≥ 0.80, p < 0.01) and group average (R² ≥ 0.74, p < 0.01) levels. In addition, we found that unilateral deficits in trailing limb propulsion induced via a leg bracing elicited unilateral and relatively proportional reductions in peak anterior GRF, peak ankle power, and peak shank acceleration. These unilateral leg bracing effects on peak shank acceleration correlated with those in peak ankle power (braced leg: R² = 0.43, p = 0.028) but those effects in both peak shank acceleration and peak ankle power were disassociated from those in peak anterior GRF. In conclusion, our findings in young adults provide an early benchmark for the development of affordable and clinically feasible alternatives for assessing and monitoring trailing limb propulsion during walking.