McNair/Gateway Scholars Program USC

Erin O'Donnell

Major and Classification

Neuroscience

Faculty Mentor

  • Lisa Aziz-Zadeh, Ph.D.

Department

  • Neuroscience

McNair Project

Biomechanical Effects of an ACL Injury Prevention Program on Lower Extremity Landing Mechanics

Differences in the performance of athletic maneuvers are a contributory factor with respect to the disproportionate incidence of non-contact anterior cruciate ligament (ACL) injuries in female athletes. One mechanism of a non-contact ACL injury is described as occurring just after foot contact during a maneuver that includes a sharp deceleration and change in direction. The biomechanical variables thought to increase an athletes risk for ACL injury include decreased knee and hip flexion angles, increased quadriceps activation, increased knee valgus angles, and increased knee adductor moments when compared to males. The purpose of this study was to determine the effects of an ACL injury prevention program on lower extremity landing mechanics and to evaluate the effect of an ACL Injury Prevention Program on knee and hip kinetics and kinematics during a drop landing task. Three dimensional kinematics, ground reaction forces (1500 Hz) and electromyo-graphic activity (surface electrodes) were recoded during the deceleration phase of a drop land in thirty soccer players. Subjects then participated in the Prevent Injury Enhance Performance (PEP) Training Program 2 times a week for 12 weeks and returned for a re-test. Differences in hip and knee joint kinematics, average moments, and average muscle EMG intensity were evaluated with paired t tests. Following participation in an ACL injury prevention program the athlete's demonstrated increased hip flexion (73.84? ? 13.09 vs 78.84 ? 14.15) and total flexion, decreases in quadriceps activity and knee valgus (6.75? ? 4.56 vs. 5.33 ? 3.95) and ratio of knee to hip (2.31 ? 1.82 vs. 1.74 ? .86) and increases of average hip extensor moments ( -.69 Nm/kg ? .22 vs. -.79 ? .23). The above results are concurrent with previous work demonstrating that changes in these actions decrease the risk for an ACL injury and can serve as effective prevention techniques. The results are promising because they reinforce the danger of "stiff landings" and establish that movement patterns can be changed to prevent documented 'at-risk' ACL rupture conditions.

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