Transtibial limb loss influences muscle excitation, 3D dynamic balance and their cross-sectional correlation in older individuals during walking.

Abstract

Two-thirds of individuals with amputations in large cities are older. Our study identifies how lower-limb amputation alters dynamic balance, muscle excitation and their relationship across samples of older individuals at multiple walking speeds. We hypothesized that individuals with amputation would express different relationships between their muscle excitation and 3D dynamic balance, which would depend on speed. Angular momenta of the body and individual segments, as well as bilateral electromyography signals of five muscles were compared between individuals with (n = 13) and without (n = 10) below-knee amputation at self-selected normal and fast speeds, using Statistical Parametric Mapping. We also related balance and muscle excitation through Pearson correlations of angular momenta and electromyography (α = 0.05). There were multiple increases (and few decreases) in whole-body and segmental angular momenta for individuals with amputation during early, mid and late stance as well as terminal swing, especially in the sagittal plane. Excitation of the medial hamstring of the residual leg in late swing was decreased at both speeds in individuals with amputations. Generally, both groups had positive correlations between muscle excitation and angular momenta. However, interesting exceptions occurred for the group with amputation such as a negative relationship between the medial hamstring of the residual limb and whole-body angular momentum in the transverse plane at normal walking speeds, where increased muscle activity was associated with more balanced individuals. Use of prostheses during walking by older individuals influences dynamic balance, muscle coordination, and their correlation. Observability of these differences depends on speed and anatomical plane.