Ankle dorsiflexor, not plantarflexor strength, predicts the functional mobility of people with spastic hemiplegia

OBJECTIVE: To determine the relationships between affected ankle dorsiflexion strength, other ankle muscle strength measurements, plantarflexor spasticity, and Timed "Up & Go" (TUG) times in people with spastic hemiplegia after stroke. DESIGN: A cross-sectional study. SETTING: A university-based rehabilitation centre. PARTICIPANTS: Seventy-three subjects with spastic hemiplegia. MAIN OUTCOME MEASURES: Functional mobility was assessed using TUG times. Plantarflexor spasticity was measured using the Composite Spasticity Scale. Affected and unaffected ankle dorsiflexion and plantarflexion strength were recorded using a load-cell mounted on a foot support with the knee bent at 50º and subjects in supine lying. RESULTS: TUG times demonstrated strong negative correlation with affected ankle dorsiflexion strength (r = -0.67, p ≤ 0.001) and weak negative correlations with other ankle muscle strength measurements (r = -0.28 to -0.31, p ≤ 0.05), but no significant correlation with plantarflexor spasticity. A linear regression model showed that affected ankle dorsiflexion strength was independently associated with TUG times and accounted for 27.5% of the variance. The whole model explained 47.5% of the variance in TUG times. CONCLUSION: Affected ankle dorsiflexion strength is a crucial component in determining the TUG performance, which is thought to reflect functional mobility in subjects with spastic hemiplegia.