Abstract
This study investigated the force-angle relationship and EMG-angle relationship in static leg extension and knee extension, and examined the correlation between these movements. A total of 16 healthy volunteers, 6 males and 10 females, with a mean age of 24.6 years, participated in this study. Static muscle strength was measured during maximal leg extension and knee extension at knee flexion angles of 15°, 30°, 45°, 60°, 75°, 90° (0° = fully extended leg). By bipolar recording using surface electrodes, rectified filtered electromyography (RFEMG) in the vastus medialis, rectus femoris and semimembranosus was obtained during each movement. All RFEMG data were normalized to a percentage of the RFEMG voltage produced during maximal isometric contraction at a knee flexion angle of 90°. As a result, the torque curve demonstrated a maximal peak value at knee flexion angles of 45°-60° in static leg extension. In static leg extension, maximal peak activity of the knee extenser was produced at a large knee angle, while that of the knee flexor was produced at a small knee angle. As to static strength, there was a significant correlation between leg extension and knee extension at large knee angles, not at small knee angles (15°, 30°). The results of this study indicate that we should consider not only knee extension exercise but also leg extension exercise.
