The relationship between walking speed, step parameters, and margins of stability in individuals after stroke

Background: Individuals after stroke walk with different step parameters and consequently with different margins of stability compared to able-bodied peers. These differences might be a side effect of lower preferred walking speeds or primary limitations in regulating step parameters and margins of stability after stroke. Methods: Twenty-eight individuals after stroke (separated into more impaired and less impaired based on speed) and fourteen able-bodied peers completed five walking trials on an instrumented treadmill at 70 %, 85 %, 100 %, 115 %, and 130 % of their preferred speed. Center of pressure data were used to calculate stride frequency, stride length, step width and margins of stability in mediolateral and anteroposterior direction. Generalized estimation equations were used to analyze the (interaction) effects of group, speed, and most versus least affected leg on these parameters. Findings: When controlled for speed, all individuals after stroke walked with higher stride frequencies (P < 0.001) and shorter stride lengths (P < 0.001) than able-bodied peers. Less impaired individuals walked with larger step widths than able-bodied peers (P < 0.001). The interaction effect of group and speed suggested that individuals after stroke showed higher increases in stride length with increasing speed than able-bodied peers. When controlled for speed, mediolateral margins of stability were larger in less impaired individuals compared to able-bodied peers, but otherwise, margins of stability did not differ between groups. Only minor differences between the most and least affected leg were observed. Interpretation: Differences in step parameters between individuals after stroke and able-bodied peers seem independent of walking speed and function to enhance gait stability.