The Influence of Knee Rotation on Electromyographic Activity of Medial and Lateral Heads of the Quadriceps Femoris Muscle during Isometric Knee Extension Effort.

Abstract

Background and Purpose: The purpose of this study was to determine the difference in the muscle activities of the Vastus Medialis Oblique (VMO), Vastus Medialis Longus (VML), Vastus Lateralis Oblique (VLO) and Vastus Lateralis Longus (VLL) with internally rotated, neutral, and externally rotated knee joint positions during isometric knee extension strength effort at 60° of knee flexion. Subjects: Seven healthy males, aged 24 to 34 years (29.3 ± 4.1), participated in this study. Methods: The subjects performed isometric knee extension with internally rotated, neutral, and externally rotated knee positions. Electromyographic (EMG) activity was detected using bipolar fine wire electrodes and was recorded from VMO, VML, VLO, VLL and the Adductor Magnus (AM). Results: The normalized integrated EMG (IEMG) of VMO, VML and AM were significantly greater in the internally rotated knee position than in the neutral knee position. The normalized IEMG of the VLO and VLL were not significantly different at each knee position. Discussion and Conclusion: VMO, VML and AM muscle activity may be altered by knee rotation position during isometric knee extension effort.