Level walking and ambulatory capacity in persons with incomplete spinal cord injury: relationship with muscle strength

Study design: Prospective analysis of relationships. Objectives: ( 1) To quantify the relationship between individual lower extremity muscle strength and functional walking measures and ( 2) to determine whether a multiple regression model incorporating lower extremity muscle strength could predict the performance of functional walking measures in persons with incomplete spinal cord injury (ISCI) living in the community. Setting: Tertiary rehabilitation center, Vancouver, Canada. Methods: In all, 22 subjects with ISCI participated. The relationship between functional walking measures ( gait speed, 6-min-walk distance, and ambulatory capacity) and muscle strength (manual tests of hip flexors/extensors/abductors, knee flexors/extensors, ankle dorsi flexors/plantarflexors, and great toe extensors) were measured by Pearson's correlation and regression procedures. Results: For both the more and less affected sides, hip flexors, hip extensors, and hip abductors produced the highest correlations with the three functional measures. The less affected hip flexor strength explained more than 50% of the variance in gait speed and 6-min-walk distance while the less affected hip extensor strength explained up to 64% of the variance in ambulatory capacity. For all three functional measures, the strength of the less affected limb was more important than that of the more affected limb. Conclusions: Lower extremity muscle strength, in particular that of hip flexors, hip extensors, and hip abductors, is an important determinant of functional walking performance.