Gender differences during downward squatting

The gender differences related to the movement strategies in the lower extremity have been investigated with frequency in the scientific literature. The use of the squatting in the rehabilitation programs is one approach of applying the exercises in closed kinetic chain. The motor strategy was studied recently in subjects with and without patellofemoral pain syndrome (PFPS) during downward squatting. The results showed differences in the kinetic and electromyography (EMG) patterns, which suggested a protecting strategy of the patellofemoral joint in subjects with PFPS. Since that females presented larger incidence of the PFPS, this study tested the hypothesis that there are gender differences in the kinematic, kinetic and EMG patterns during downward squatting. Sixteen healthy subjects (8 females and 8 males) participated in the study. They was asked to performer the half squatting (0? to 70? of the knee flexion), with restriction of the movements in the sagittal plane. EMG responses of the vastus medialis oblique, vastus medialis longus, vastus lateralis, biceps femoris, gastrocnemius lateralis and tibialis anterior were registered. For the analysis of the movement, the LEDs were fixed in the center of the joints of the shoulder, hip, knee and ankle and registered by a three-dimensional optical system. A force plate registered the reaction forces. The center of pressure (COP) was calculated and reported as a percentage of the longitudinal foot length. The knee and ankle joint torques was calculated by the inverse dynamics. The average of the displacement of COP, of the torques, and of the EMG signs was calculated in eight phases of the movement based on the knee and ankle velocities. The groups presented the same kinematic behavior (linear and angular displacements). However, compared to females, the males had larger ankle joint torque and smaller knee joint torque. Also, the EMG activity of the components of the quadriceps was smaller in the females than males. This suggests that females have the increase of the patellofemoral stress. The gender differences observed suggests that the major incidence in females can be explained partly by the kinetic and EMG patterns.