Effects of an Intervention Program on Lower Extremity Biomechanics in Stop-Jump and Side-Cutting Tasks

Abstract

Background: Anterior cruciate ligament (ACL) injury is one of the most common injuries in sport. To reduce the risk of noncontact ACL injury, it is critical to understand the effects of an intervention program on neuromuscular control–related biomechanical risk factors. Hypothesis: A newly developed 4-week intervention program would significantly increase the knee flexion angle at peak impact posterior ground-reaction force and would significantly decrease the peak impact posterior and vertical ground-reaction forces in the stop-jump and side-cutting tasks, while the intervention effects would be retained after the training was completed. Study Design: Controlled laboratory study. Methods: A total of 22 male and 18 female collegiate basketball and volleyball players with biomechanical characteristics associated with increased risk of ACL injury were recruited and randomly assigned to either the intervention group or the control group. The intervention group executed a program to improve landing techniques through strength and plyometric training 3 times a week for 4 weeks while participating in their regular training. The control group participated in only their regular training for 4 weeks. Three-dimensional kinematic and kinetic data in the stop-jump and side-cutting tasks were collected at week 0 (the beginning of the study) and at the ends of weeks 4, 8, 16, and 20. Knee flexion angle and ground-reaction forces were calculated. Analyses of variance with a mixed design were performed to determine the intervention effects and the retention of intervention effects for each sex. Results: Male participants in the intervention group significantly increased the knee flexion angle at peak impact posterior ground-reaction force in the stop-jump task at weeks 8, 12, and 20 when compared with that at week 0 and with the male control group ( P ≤ .002). No significant intervention effects on knee flexion angle and ground-reaction force were found in the side-cutting task for male participants. No significant interaction effects on takeoff velocities were detected in any task for male participants. No significant intervention effects on knee flexion angle and ground-reaction force were found in any task for female participants. Vertical takeoff velocity in the stop-jump task was significantly lower in the intervention group at week 20 compared with the control group ( P = .011). Conclusion: A 4-week intervention program significantly increased the knee flexion angle at peak impact posterior ground-reaction force of male collegiate athletes in the stop-jump task without significant effect on the performance of the task. This intervention effect was retained for at least 16 weeks after the training was completed. The intervention program, however, did not affect knee flexion angle and ground-reaction force in any task for female collegiate athletes. A reduction in vertical takeoff velocity of the stop-jump task was observed for female collegiate athletes 16 weeks after the intervention. Clinical Relevance: The intervention program with strength conditioning and plyometric exercises could modify landing biomechanics of male collegiate athletes in a stop-jump task. The intervention program may be a useful tool for preventing noncontact ACL injury for male collegiate athletes.