Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/19784
Sport participation is a good way to increase physical fitness but it has its downsides, mainly in the form of injuries. Anterior cruciate ligament (ACL) injury can have many implications for athletes and their sport participation. The frequency of noncontact ACL injury is higher amongst females than males. It has been suggested that anomalies in neuromuscular activities of the lower extremities are one of the risk factors for this injury. Results show that the mechanism of injury involves a multiplanar knee joint loading when the knee is almost fully extended, in a valgus position and the hip is internally rotated and adducted. This knee kinematic is often seen during landing and cutting in sports and one of the muscles that may influence the degree of adduction and internal rotation of the hip is gluteus medius. Therefore, the aim of this study is to identify whether there is a gender difference in stance duration and in neuromuscular activation of the gluteus medius during drop jump and cutting maneuver in 11-12 years old athletes. Furthermore, the aim was to evaluate the effects of fatigue on those variables.
Methods: Participants were 47 football and handball players of both genders (males=9, females=36) Surface electrodes were used to collect electromyography (sEMG) activity of gluteus medius during drop jump and cutting maneuver before and after a fatigue protocol. Activation was normalized to that obtained during a maximal voluntary isometric contraction (MVIC) and peak sEMG signals during performance were identified. Initial contact (IC) on a force plate was used as a reference point (set at zero), as was stance duration during task performance, when doing the statistical analysis.
Results: Drop jump: Stance duration was significantly longer for males than females (p=0.027) with no significant effect of fatigue. Females demonstrated an early first peak sEMG more frequently than males (p<0.001) and its normalized amplitude was significantly larger for females compared to males (p=0.003), with no significant effect of fatigue protocol. The peaks that occurred later were significantly delayed for the males after the fatigue protocol (p=0.002). Cutting maneuver: There was significant difference in the change of stance duration after the fatigue protocol (p<0.001) where the males’ stance duration increased (p=0.005) while the females’ stance duration decreased (p<0.001). Females demonstrated an early first peak sEMG more frequently than males (p<0.001). The peaks that occurred later were more delayed among females than males (p=0.020). The post-fatigue change in the amplitude of the first peak after IC, was significantly different between genders (p<0.001) where the amplitude for the males increased significantly (p<0.001) but not for females (p=0.053).
Conclusion: These results show a difference between genders in stance duration during drop jump and cutting maneuver as well as in the activation pattern of gluteus medius. Pre-pubescent females demonstrated shorter stance duration, they activated the gluteus medius muscle earlier and of greater amplitude than the pre-pubescent males and the fatigue protocol affected the genders differently. These results indicate that preventive programs that are used to reduce risk of ACL injury should be implemented at an earlier age since there is gender difference already at 11-12 years old.