Characterization of Reactions to Laterally Directed Perturbations in People With Chronic Stroke.

Abstract

Reactive balance control is often impaired poststroke. Studies addressing responses to laterally directed perturbations in this population are currently lacking. Given that stroke-related motor impairments are unilateral, a better understanding of reactive balance responses to these types of perturbations is critical. This study aimed to quantify differences in reactive balance control in response to laterally directed perturbations in people with chronic stroke, based on perturbation direction and ability to step with either limb. This study used a cross-sectional design. Participants with chronic stroke (N=19) were divided into groups representing their ability to step with either limb, based on performance on a reactive balance task in a baseline assessment. The preferred stepping limb was also identified during this assessment. Each participant then underwent a series of laterally directed perturbations on a motion platform. Behavioral measures were compared between platform direction and group. Trials with extra steps, step initiation with the preferred limb, and crossover steps were more common with platform motion toward the preferred limb compared to the nonpreferred limb; the latter effect was only observed for participants with an impaired ability to step with either limb. Side-step sequences were more common in those able to step with either limb when the platform moved toward the preferred limb. The participant sample was likely higher functioning than the general population of stroke survivors due to equipment constraints. Additionally, participants may have developed strategies to use the platform's motion characteristics to aid with balance recovery. These findings provide an indication of responses to laterally directed perturbations in people with chronic stroke and may help inform strategies for improving reactive balance control during stroke rehabilitation.