ABSTRACT
INTRODUCTION: The purposes of this study were (1) to compare the effect between contact force [first and second ground reaction force (GRF)] and decision making (anticipation vs unanticipation) on lower extremity biomechanics during a side-cutting maneuver in young soccer players; and (2) to identify which condition is more vulnerable to biomechanical risk factors of the anterior cruciate ligament (ACL) injury. MATERIALS AND METHODS: Sixteen young, male middle school soccer players with right leg dominance participated in this study. Three-dimensional motion analysis featuring GRF and electromyography (EMG) of the right leg was used during the stance phase of the side-cutting maneuver. Kinematics, kinetics, and EMG data for each athlete were analyzed and averaged for three successful anticipated and unanticipated side-cutting maneuvers. RESULTS: GRF was smaller and muscle activities were lower in most muscle groups in the first peak than that of the second peak. More flexion and internal rotational angles of the hip joint were observed in the unanticipated first peak that that of the second peak. Lesser flexion angle and moment of the knee joint observed in the first peak than that of the second peak, and abduction moment was increased after the unanticipation. CONCLUSION: The GRF and muscle activities were smaller in the first peak than those in the second peak; however, first peak showed a closer association with biomechanical risk factors of the ACL injury. There were some interactions between contact force and decision making and unanticipation made the first peak more risky to the ACL injury.
