Correlation between the angle of lateral tibial rotation and the ratio of medial and lateral hamstring muscle activities during standing knee flexion

Abstract

[Purpose] This study investigated the correlation between the angle of lateral tibial rotation and the ratio of the medial and lateral hamstring muscle activities during standing knee flexion. [Subjects] Eighteen healthy subjects (6 females, 12 males) participated in this study. [Methods] Surface electromyography was used to record medial and lateral hamstring muscle activities, and the muscle activities were expressed as a percentage of the reference voluntary contraction. The angle of tibial rotation was measured with a three-dimensional motion analysis system. Subjects were instructed to perform knee flexion on one side in the standing position. Pearson's correlation coefficient was used to test the relationship between the angle of the lateral tibial rotation and the ratio of the activity of the medial and lateral hamstring muscles during standing knee flexion. [Results] The angle of the lateral tibial rotation and the ratio of the medial and lateral hamstring muscle activities showed good to excellent correlation (r = -0.767). [Conclusion] These results suggest that asymmetry of the medial and lateral hamstring muscle activities may cause tibial lateral rotation during standing knee flexion.