The relationship of lower extremity strength and gait parameters in patients with post-polio syndrome.

Relationships between lower extremity strength and stride characteristics were studied in 24 patients with post-polio syndrome. Maximum isometric torques were measured in the ankle plantar flexors, hip and knee extensors, and hip abductors. Gait velocity, stride length, and cadence were recorded during free and fast walking. Step-wise regression analysis was performed to determine which muscle groups best predicted ambulatory function. Plantar flexion torque was the best predictor of velocity (r = .55 free walking and r = .76 fast) and cadence (r = .46 free and r = .58 fast). The combination of plantar flexion and hip abduction torques was the best predictor of fast stride length (r = .78). These findings emphasize the important role of the plantar flexor muscles in gait. Knee extension torque was the poorest predictor for each of the gait parameters. Several patients demonstrated gait deviations that minimized the penalty of quadriceps weakness. Without a contracture or an orthosis, however, no adequate substitution exists for weak plantar flexion.