Muscle strength is only a weak to moderate predictor of gait performance in persons with late effects of polio.

OBJECTIVE To assess muscle strength in the knee extensors, knee flexors and ankle dorsiflexors in persons with late effects of polio, and determine how much muscle strength, gender, age and BMI are related to gait performance. METHODS Ninety community-dwelling ambulant persons (47 men and 43 women; mean age 64 years SD 8) with late effects of polio participated. Isokinetic concentric knee extensor and flexor muscle strength was measured at 60°/s and ankle dorsiflexor muscle strength at 30°/s. Gait performance was assessed by the Timed "Up & Go", the Comfortable and Fast Gait Speed tests, and the 6-Minute Walk test. RESULTS There were significant correlations between knee extensor and flexor muscle strength and gait performance (p < 0.01), and between ankle dorsiflexor muscle strength and gait performance (p < 0.05), for both lower limbs. Muscle strength in the knee extensors and flexors explained 7% to 37% and 9% to 47%, respectively, of the variance in gait performance. Strength in the ankle dorsiflexors explained 4% to 24%, whereas gender, age and BMI contributed at most an additional 9%. CONCLUSION Knee muscle strength, and to some extent ankle dorsiflexor muscle strength, are predictors of gait performance in persons with late effects of polio, but the strength of the relationships indicates that other factors are also important.