Post-stroke deficits in the step-by-step control of paretic step width

•Dynamics-dependent adjustments in step width are important for a stable gait.•The link between paretic step width and pelvis dynamics is weakened post-stroke.•The mediolateral margin of stability is larger and more variable for paretic steps.•Increased step-by-step control of step width may improve post-stroke gait balance. Humans partially maintain gait stability by actively controlling step width based on the dynamic state of the pelvis – hereby defined as the “dynamics-dependent control of step width”. Following a stroke, deficits in the accurate control of paretic leg motion may prevent use of this stabilization strategy. Do chronic stroke survivors exhibit paretic-side deficits in the dynamics-dependent control of step width? Twenty chronic stroke survivors participated in this cross-sectional study, walking on a treadmill at their self-selected (0.57 ± 0.25 m/s; mean ± s.d.) and fastest-comfortable (0.81 ± 0.30 m/s) speeds. To quantify the dynamics-dependent control of step width, we calculated the proportion of the step-by-step variance in step width that could be predicted from mediolateral pelvis dynamics, and used partial correlations to differentiate the relative effects of pelvis displacement and velocity. Secondarily, we calculated the mean and standard deviation of more traditional gait metrics: step width; lateral foot placement; and mediolateral margin of stability (MoS). We used repeated measures ANOVA to test for significant effects of leg (paretic vs. non-paretic) and speed (self-selected vs. fastest-comfortable) on these measures. Relative to non-paretic steps, paretic steps exhibited a weaker (p ≤ 0.005) link between step width and pelvis dynamics, attributable to a decreased partial correlation between step width and pelvis displacement (p ≤ 0.001). Paretic steps were also placed more laterally (p