Does the rate of hip abductor and adductor muscle activation during weight transfer influence voluntary lateral stepping in chronic stroke?

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 =  - 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.