Contribution of ankle dorsiflexor strength to walking endurance in people with spastic hemiplegia after stroke

Objectives: (1) To determine the relationships of ankle dorsiflexor strength, ankle plantarflexor strength, and spasticity of the ankle plantarflexors with walking endurance; (2) to determine whether affected ankle dorsiflexor strength makes an independent contribution to walking endurance; and (3) to quantify its relative contribution to the walking endurance of people with spastic hemiplegia after stroke. Design: A cross-sectional study. Setting: University-based rehabilitation center. Participants: Subjects (N=62) with spastic hemiplegia. Interventions: Not applicable. Main Outcome Measures: Walking endurance was measured by the distance covered in the six-minute walk test (6MWT). Ankle dorsiflexor and plantarflexor strength were measured using a load-cell mounted on a custom-built foot support. Plantarflexor spasticity was measured using the Composite Spasticity Scale. Results: The six-minute walk distances showed stronger positive correlation with affected dorsiflexor strength (r=.793, P≤.000) when compared with affected plantarflexor strength (r=.349, P=.005). Results of the regression model showed that after adjusting for basic demographic and stroke-related impairments, affected ankle dorsiflexor strength remained independently associated with six-minute walk distance, accounting for 48.8% of the variance. Conclusions: This is the first study, to our knowledge, to document the importance of ankle dorsiflexor strength as an independent determinant of walking endurance in stroke survivors with spastic plantarflexors. Our findings suggest that stroke rehabilitation programs aiming to improve walking endurance should include strengthening exercises for the ankle dorsiflexors.