Abstract
People with chronic stroke (PwCS) suffer from impaired lateral weight transfer, resulting in a loss of balance. The primary purpose of this study was to examine how stroke impairs the rate of hip abductor-adductor muscle activation during weight transfer compared to controls, and whether this influences subsequent stepping performance. The secondary purpose was to determine how stroke affects bilateral coordinated hip abductor-adductor muscle activity between the step and stance legs. 20 PwCS (61.6 ± 7.4 years, 4F/16 M) and 10 healthy controls (64.8 ± 8.9 years, 5F/5M) were included. Participants took a voluntary lateral step, as quickly as possible, in response to a light cue. Bilateral Adductor Longus (ADD) and Gluteus Medius (GM) rate of muscle activation (RoA) were measured using electromyography, and spatiotemporal step characteristics were measured using motion capture. Paretic (p < 0.01) and non-paretic (p < 0.01) stance and step legs had a reduced GM and ADD RoA during weight transfer compared to controls. Reduced stance and step GM and ADD RoA were associated with longer weight transfer and step initiation times (r(s) = - 0.47 to - 0.63, p < 0.001). PwCS had a lack of bilateral coordinated GM and ADD activity (p > 0.05). Post-stroke reductions in GM and ADD RoA contribute to altered step characteristics.