Lower limb muscle power relationships in bilateral able-bodied gait.

OBJECTIVE: The purpose of this study was to test the hypothesis that limb propulsion is mainly associated with the interaction of a number of muscle power bursts developed throughout the stance phase and that the control actions are mainly achieved by the contralateral limb through different power-burst interactions. We also hypothesized that the power activities of the propulsion limb would be related to those of the control limb. DESIGN: Sixty gait trials of 20 subjects with dominant right hands and right legs were chosen for analysis. Each trial represents a performance of an able-bodied gait. Data were assessed using an eight-camera, high-speed, video-based system synchronized to two force plates. The muscle powers and their related mechanical energies were calculated at each joint and in each plane of the lower limbs by use of an inverse dynamic technique. The Pearson correlation method was used to determine the relationships within each limb by use of the data identified by principal component analysis, whereas a canonical correlation analysis was performed to illustrate the interaction between the limbs. RESULTS: Gait propulsion was an activity initiated by the hip shortly after heel-strike and maintained throughout the stance phase. Control was the main task of the left limb as evidenced by the power absorption bursts at the hip and knee. The left limb power generations were generally secondary to control activities and were possibly involved in adjustments to correct the other limb's propulsion. Interlimb interaction further emphasized the functional relationship between forward progression and control tasks developed by each limb and highlighted the importance of the frontal and transverse plane actions during gait. CONCLUSION: These results do not support the hypothesis that the ankle was a major contributor to forward progression.