Gait asymmetry pattern following stroke determines acute response to locomotor task

Background: Given the prevalence of gait dysfunction following stroke, walking recovery is a primary goal of rehabilitation. However, current gait rehabilitation approaches fail to demonstrate consistent benefits. Gait asymmetry, prevalent among stroke survivors who regain the ability to walk, is associated with an increased energy cost of walking and is a significant predictor of falls post-stroke. Furthermore, differential patterns of gait asymmetry may respond differently to gait training parameters. Research question: The purpose of this study was to determine whether differential responses to locomotor task condition occur on the basis of step length asymmetry pattern (Symmetrical, NPshort, P-short) observed during overground walking. Methods: Participants first walked overground at their self-selected walking speed. Overground data were compared against three task conditions all tested during treadmill walking: self-selected speed with 0% body weight support (TM); self-selected speed with 30 % body weight support (BWS); and fastest comfortable speed with 30 % body weight support and nonparetic leg guidance (Guidance(NP)). Our primary metrics were: symmetry indices of step length, stride length, and single limb support duration. Results: We identified differences in the response to locomotor task conditions for each step length asymmetry subgroup. GuidanceNP induced an acute spatial symmetry only in the NPshort group and temporal symmetry in the Symmetrical and Pshort groups. Importantly, we found the TM and BWS conditions were insufficient to impact either spatial or temporal gait symmetry. Significance: Task conditions consistent with locomotor training do not produce uniform effects across subpatterns of gait asymmetry. We identified differential responses to locomotor task conditions between groups with distinct asymmetry patterns, suggesting these subgroups may require unique intervention strategies. Despite group differences in asymmetry characteristics, improvements in symmetry noted in each group were driven by changes in both the paretic and nonparetic limbs.