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bioRxiv · 10.1101/2020.05.06.080705

Effects of targeted assistance and perturbations on the relationship between pelvis motion and step width in people with chronic stroke

Reimold, N. K.·Knapp, H. A.·Chesnutt, A. N.·Agne, A.·Dean, J. C.
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Abstract

BackgroundPeople with chronic stroke (PwCS) often exhibit a weakened relationship between pelvis motion and paretic step width, a behavior important for gait stabilization. We have developed a force-field able to manipulate this relationship on a step-by-step basis. ObjectiveThe objective of this study was to investigate the effects of a single exposure to our novel force-field on the step-by-step modulation of paretic step width among PwCS, quantified by the partial correlation between mediolateral pelvis displacement at the start of a step and paretic step width (step start paretic {rho}disp). MethodsFollowing a 3-minute period of normal walking, participants were exposed to 5-minutes of either force-field assistance (n=10; pushing the swing leg toward a mechanically-appropriate step width) or perturbations (n=10; pushing the swing leg away from a mechanically-appropriate step width). This period of assistance or perturbations was followed by a 1-minute catch period to identify any after-effects, a sign of sensorimotor adaptation. ResultsWe found that assistance did not have a significant direct effect or after-effect on step start paretic {rho}disp. In contrast, perturbations directly reduced step start paretic {rho}disp (p=0.004), but were followed by an after-effect in which this metric was increased above the baseline level (p=0.02). ConclusionsThese initial results suggest that PwCS have the ability to strengthen the link between pelvis motion and paretic foot placement if exposed to a novel mechanical environment, which may benefit gait stability. Future work is needed to determine whether this effect can be extended with repeated exposure to force-field perturbations.

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Reimold, N. K., Knapp, H. A., Chesnutt, A. N., Agne, A., Dean, J. C.. 2020-05-08. Effects of targeted assistance and perturbations on the relationship between pelvis motion and step width in people with chronic stroke. https://doi.org/10.1101/2020.05.06.080705

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