Gender differences in time-frequency EMG analysis of unanticipated cutting maneuvers

The purpose of this study is to compare the time-frequency characteristic, using nonlinearly scaled wavelets, of the EMG signal as well as the three-dimensional (3D) knee kinematics of female and male elite soccer players performing an unanticipated cutting maneuver.

Fifteen female and 15 male elite soccer players performed several cutting maneuvers during which EMG of eight muscles of the leg and 3D kinematics of the knee were recorded. To create an unanticipated condition, the participants executed one of three tasks, which were signaled to them with an illuminated target board.

Male participants generally executed the unanticipated cutting maneuver with a quadriceps activation of higher frequency components. These gender differences were also found at initial ground contact (IC) for the vastii and biceps femoris (BF) muscles. These higher frequencies dominated the signal earlier in time for the BF and later for the tibialis anterior (TA) in women. Furthermore, women performed the cutting task with greater knee abduction than did the men.

Female athletes adopted a different motor unit recruitment strategy that was particularly evident at, and near, IC resulting in lower frequency components in the EMG signal of the lateral hamstring. This strategy may play a role in explaining the gender bias in anterior cruciate ligament (ACL) injury rates. Gender differences in knee kinematics were also observed, exposing the female ACL to higher strain, which may be the result of differences in neuromuscular strategies to stabilize the knee joint.