INTRODUCTION: Stroke is a long-term adult disability, with 80% of stroke survivors experiencing gait impairments. Interventions that manipulate walking conditions, such as Asymmetric surface stiffness walking have shown to induce neuromotor adaptation and improve gait symmetry. However, these adaptations have previously been assessed through treadmill-based aftereffects, which may not accurately reflect functional overground gait. Additionally, most work has focused on weight-bearing symmetry rather than neuromuscular response. Therefore, this study evaluated the transfer of aftereffects in lower limb muscle activity from symmetric surface stiffness treadmill walking to overground walking. 

METHODS: 5 healthy individuals completed a speed test trial on a 12.5m overground walkway to determine their preferred walking speed. Participants then completed three baseline walking trials on the same walkway. Next, participants walked for 12-minutes on an adjustable surface stiffness treadmill (AdjuSST), with a 2-minute acclimation period followed by a 10-minute adaptation period. During adaptation, one leg walked on a rigid belt (300 kN/m) while the contralateral leg walked on a compliant belt (15 kN/). After effects were assessed during a 5-minute post-condition while participants walked overground.

RESULTS: During adaptation, changes in muscle activation were observed between the limbs relative to baseline walking. By late adaptation, participants demonstrated changes in gait symmetry consistent with neuromotor adaptation. During the post condition, alterations in lower limb muscle activity persisted as participants transitioned to overground walking. 

CONCLUSIONS: These results indicate that asymmetric stiffness surface walking produced aftereffects in lower limb muscle activation that transferred to overground walking. Further research is needed to evaluate whether these adaptations persist following repeated interventions.