Narrow base walking to challenge mediolateral stability in people with chronic stroke.

BACKGROUND: People with chronic stroke (PwCS) often adopt a wider gait to compensate for impaired balance, which may serve to accommodate larger extrapolated center of mass (XCoM) excursion. Narrow base walking constrains this strategy, potentially revealing balance deficits not evident during regular walking. This study aimed to evaluate mediolateral stability of PwCS during narrow base walking compared to healthy individuals. METHODS: Nineteen PwCS and sixteen healthy individuals walked on a virtual beam (60, 40, or 20 cm) on the treadmill. Participants were instructed to place their feet within the beam as accurately as possible. Marker data were obtained using three-dimensional motion capture. Effects of group, condition, and their interaction on XCoM excursion, step width, and the mean and variability of the mediolateral margin of stability were assessed using linear mixed models. FINDINGS: A significantly lower task accuracy was observed for the paretic leg (84%) at 20 cm compared to the non-paretic leg (98%) and healthy individuals (100%). Compared to healthy individuals, PwCS had a 0.03-0.04 m greater XCoM excursion and 0.06-0.07 m wider steps during all three beam conditions (all p's < 0.001). The mean and variability of the mediolateral margin of stability were higher in PwCS compared to healthy individuals, both at the paretic and non-paretic leg. INTERPRETATION: PwCS showed poorer performance during narrow base walking than healthy individuals. This was likely due to a combination of sensorimotor impairment affecting the ability to reduce XCoM excursion and a prioritization of stability over task accuracy.