Mechanical Characteristics Of Knee And Activity Characteristics Of Knee Muscles During Flexion And Extension At Different Hip Angles

Purposes: Through this experiment, exercises were carried out on a isokinetic machine, and at the same time bipolar electromyographic signals (sEMG) were recorded from surface electrodes on major muscles of knee at varying hip angles. The aim of this study was to verify the mechanical characteristics of knee and the activity characteristics of knee muscles during flexion and extension exercise at different hip angles. The author wants to afford relevant date for anatomy.Methods: Eleven young healthy men volunteered to participate in the study. They performed maximum isometric and isokinetic knee flexion and extention contraction at three positions of varying hip angles. Subjects were requested to perform the following tasks:(1)maximal voluntary isometric contractions at knee joint 30°,60°and 90°(0°=full extention);(2)maximal flextion and extention isokinetic concentric contraction at 60°,120°,and 180°/s; (3) maximal flextion and extention isokinetic eccentric contraction at 60°and 120°/s. Simultaneously, the sEMG signals were recorded from retus femoris,vastus medialis,vastus lateralis,and biceps femoris muscles. Peak torque and average power were calculated as mechanical parameter; Normalized root mean square(RMS)of sEMG was calculated as an index of sEMG amplitude.Results: In maximal voluntary isometric contraction mode, at different hip angles, PT, F/E and AP show remarkable diversity. In isokinetic concentric mode, at the same velocity and different hip angles, the muscle force and the surface electric signal index of flexor show remarkable diversity. In isokinetic eccentric mode,at the same velocity and different hip angles, the muscle force of extensor show remarkable diversity,but the surface electric signal index show no significant diversity.Conclusions: In maximal voluntary isometric contraction mode, knee-joint stretches and the surface electric signal index of muscle are not only due to knee-joint angle, also due to hip-joint angle; in knee concentric exercise, the different angles of hip, knee flexor force and surface EMG indicators showed significant changes; in isokinetic eccentric exercise, at the different angles of hip, there are no significant changes in knee muscle EMG parameters.