The efficacy of carbon fiber insoles to enhance mechanical leverage during walking does not vary with navicular drop-derived foot mobility.

Many age-related gait changes (i.e., shorter steps, slower speeds, higher metabolic rate, instability) may be precipitated at least in part by reduced push-off intensity and a diminished ability to regulate foot-ankle leverage during walking. Carbon fiber insoles (CFIs) have been shown to improve foot-ankle leverage in younger and older adults in group average comparisons. The purpose of this study in n = 20 younger adults and n = 20 older adults was to determine whether the efficacy of CFIs to enhance foot-ankle leverage during walking depends on passive structural midfoot mobility, measured here using the sit-to-stand navicular drop test (NDT). We hypothesized that greater NDT values, indicative of greater passive midfoot mobility, would correlate with greater increases in foot-ankle leverage when walking with CFIs versus standardized footwear. We defined the change in foot-ankle leverage using that of the peak external moment arm of the ground reaction force (ΔRext) and peak ankle moment (ΔMank) and examined two CFI stiffnesses (i.e., kmed and khigh). In contrast to our hypothesis, we found no statistically significant associations (p > 0.05) between passive midfoot mobility (i.e., NDT values) and enhanced leverage outcomes (ΔRext and ΔMank) induced by CFIs. This apparent lack of individual specificity suggests either that: (i) personalized prescription may require dynamic evaluation of midfoot mobility or (ii) generalized prescription of CFIs, without the requisite need for personalized stiffness construction, may improve foot-ankle leverage to mitigate age-related gait changes.