The Muscle Activation Characteristics of Knee and Ankle During 45° Side-step Cutting Task under Different Approach Run Speeds

Objective: To compare the differences of muscle activation characteristics of knee and ankle between male and female participants under different approach run velocities. In addition, the correlation between pre co-activation ratio and post co-activation ratio of muscles in knee and ankle joint was further analyzed. Methods: Forty-six youth basketball and volleyball players completed 45° side-step cutting task at 3, 4 and 5 m/s, respectively. Delsys wireless surface electromyography (EMG) was used to collect the EMG signals of quadriceps (rectus femoris, vastus medialis and vastus lateralis) , hamstrings (biceps femori long head and short head, semitendinosus) , tibialis anterior and lateral gastrocnemius. The normalized root-mean-square amplitudes and the co-activation ratio of knee and ankle muscles in the pre-activation and post-activation phases at three approach run velocities were analyzed. Results: The approach run velocities significantly increased the activation levels of quadriceps and lateral gastrocnemius during the pre-activation phase (P<0.05) , the activation levels of quadriceps, hamstring, tibialis anterior and lateral gastrocnemius muscles during the post-activation phase (P<0.05) , but significantly reduced the muscle co-activation ratio of the knee and ankle in the pre-activation phase (P<0.05) . The activation level of quadriceps and tibialis anterior muscle in females were significantly higher than that of the males (P<0.05) during pre-activation and post-activation phases, but muscle co-activation ratio of the knee in females during pre-activation and post-activation phases was significantly lower than in males (P<0.05) . Muscle co-activation ratio in knee and ankle was significantly correlated between pre-activation and post-activation phase (P<0.05) . Conclusions: With increasing approach run speed, central nervous system increased the muscle activation level by adjusting the pre-activation and post-activation mechanisms. There was moderate to high correlation between the pre-activation and post-activation mechanisms in the 45° side-step cutting task, which suggests that the coordination of pre-activation and post-activation can adjust the stiffness of muscles and joints to protect the joints and tissues of the lower extremities and to improve the athletic performance. The lower knee joint muscles co-activation ratio in post-activation phase quadriceps dominant activation pattern suggested that the females may suffer higher risk of ACL injury in 45° than their male counterparts. To some extent, gender difference in activation patterns of the knee muscles may explain the gender difference in ACL injury risk.