Contributions of lower-limb muscle power in gait of people without impairments.

BACKGROUND AND PURPOSE Although gait asymmetry in rehabilitation has been documented, little is known about propulsion and control tasks performed by each limb and how these tasks are managed between the lower limbs. The purpose of this study was to test the hypothesis that the leading limb contributes mainly to forward progression, whereas the trailing limb provides control and propels the lower limb to a lesser extent. SUBJECTS Nineteen men with an average age of 26.2 years (SD=3.2, range=21-34) and no history of orthopedic ailments participated in the study. METHODS Muscle power was determined using an 8-camera high-speed video system synchronized with 2 force plates. The principal-component analysis method was applied to reduce and classify 52 gait variables for each limb, and Pearson correlations were used to determine the interactions within the data sets for each limb. RESULTS Gait propulsion was initiated by the hip of the leading limb shortly after heel-strike and was maintained throughout the stance phase. Control was the main task of the trailing limb, as evidenced by the power absorption bursts at the hip and knee. CONCLUSION AND DISCUSSION Within-limb interaction further emphasized the functional relationship between forward progression and control tasks and highlighted the importance of frontal- and transverse-plane actions during gait.