INTRODUCTION: Stroke, a leading cause of long-term disability, leaves 40% of individuals with moderate functional impairments, and many with severe impairments [1]. Reduction, mistiming, or altered durations in muscle activation have been observed in the paretic limb. Dual-belt speed interventions have produced improvements in temporal gait outcomes, however changes in muscle activation are small [2]. Asymmetric surface stiffness walking has the potential to improve these outcomes. PURPOSE: To explore the effects of a single bout of asymmetric surface stiffness walking on muscle activity. METHODS: 10 healthy individuals completed 3 walking bouts in one session at 1.25 m/s. Participants completed a 5-minute baseline on a dual-belt instrumented treadmill (Bertec, Columbus, OH, USA), then 12 minutes on an adjustable surface stiffness treadmill (AdjuSST), with a 2-minute acclimation, then a 10-minute adaptation period. We assessed aftereffects during a 5-minute post-condition, presented as an asymmetry ratio (SI) over a 20-stride window at the end of the baseline, and the beginning and end of the post-condition.  RESULTS: A significant increase in plantarflexor muscles was seen early-post compared to baseline (Lateral Gastrocnemius: SI_baseline=0; SI_early-post=18.28, Soleus: SI_baseline=0; SI_early-post=12.15). No significant changes in knee extensor muscle activity were observed. CONCLUSIONS: These results indicate that a single bout of asymmetric surface stiffness walking produces triceps surae muscle group aftereffects during normal walking. Further research involving individuals post-stroke is needed to evaluate if this intervention can improve their plantar-flexor activation and paretic propulsion.  

REFERENCES: [1] Duncan et al. (2005). Stroke, 36(9); [2] Rozanski et al. (2020). Clin Neurophysiol, 131(8).