Electromyographic analysis of the knee during jump landing in male and female athletes

Many noncontact anterior cruciate ligament (ACL) injuries in female athletes occur at foot strike during jump landing when the knee is extended. This study was undertaken to determine the activation level of the quadriceps and hamstring muscles electromyographically. Fifteen healthy volunteers (eight women and seven men), all of whom were collegiate basketball players, participated in the study. The maximum voluntary contraction (MVC) of the vastus medialis (VM) at a knee flexion angle of 15-45° was significantly higher in women than in men. There was no significant difference in overall mean hamstring activity in men and women over the same knee flexion range. However, when the knee flexion angle was 15°, 20°, and 25°, hamstring activity was significantly lower in female athletes. These results suggest that female athletes have a higher risk of ACL injury during jump landing due to increased anterior tibial translation force with quadriceps muscle activity. Female athletes require greater hamstring activation, and it is suggested that exercising this muscle will increase its activity when the knee is extended, thus preventing ACL injury during actual sport motions.