Relationship between the rate of force development in knee extensor muscles and gait speed in patients with chronic stroke: A cross-sectional study.

BACKGROUND: The relationship between peak torque of the knee extensor muscles and gait speed was previously investigated in patients with chronic stroke, but whether the rate of force development (RFD), another indicator of muscle strength, affected gait speed remained unknown. OBJECTIVE: To clarify the relationships between the RFD of the knee extensor muscles over multiple time intervals and gait speed in patients with chronic stroke. METHODS: Twenty chronic stroke patients participated in this study. The RFD of affected and unaffected knee extensor muscles was measured. Time intervals of the RFD were set to 0-50 ms, 0-100 ms (100RFD), 0-200 ms (200RFD), and 0-300 ms (300RFD). Gait speed was assessed at comfortable and maximum pace. Pearson correlation coefficient (r) was used to analyze the relationships between RFD and gait speeds. RESULTS: The RFD of affected knee extensor muscles over all intervals was moderately correlated with both comfortable and maximum gait speeds, whereas only limited combinations (100, 200 and 300RFD with maximum gait speed) were correlated on the unaffected side. CONCLUSIONS: The present results suggest that various factors related to the RFD of affected knee extensor muscles, such as neural drive and muscle size, affect gait speed.