It is well established that female athletes are at increased risk for sustaining ACL injuries in sports, where sudden changes of direction are a frequent movement pattern. The underlying neuromuscular mechanisms related to the elevated ACL injury rate in female athletes has yet to be fully investigated. This cross-sectional study aimed to examine gender differences in neuromuscular pre-activity during a maneuver that mimics a movement associated with the incidence of ACL injuries. Twenty-four team handball players (12 male and 12 female) with no history of ACL injury were tested for EMG pre-activity of vastus lateralis, vastus medialis, semitendinosus, and biceps femoris during a side-cutting maneuver. Mean EMG amplitude 50 ms prior to toe down was normalized to maximal EMG obtained during maximal isometric contraction. The results showed that females had significantly lower hamstring EMG pre-activity 50 ms prior to toe-down than males (P < 0.01). No gender difference was present in quadriceps EMG pre-activity during side-cutting. Lower hamstring activation prior to toe-down may result in lower hamstring contraction force during the initial part of the ground contact, and thus lesser knee joint stability compared to males. Specific training should be employed to alter the neuromuscular coordination towards a more stabilizing motor pattern.
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