The effect of different exercise training interventions on lower extremity biomechanics and quality of movement in high school female athletes

Context: Anterior cruciate ligament (ACL) injuries are common in adolescent and adult female athletes and are believed to be related to poor neuromuscular control. Neuromuscular deficits manifest through biomechanics during dynamic tasks such as landing from a jump. Alterations in biomechanical patterns have been shown as a result of neuromuscular training programs. It is unknown which component of these programs are responsible for the neuromuscular alterations. Objective: To assess the efficacy of either a 4 week core stability program or plyometric program on altering lower extremity and trunk kinetics and kinematics during a drop vertical jump (DVJ). Design: Cohort study. Setting: High school athletic field and motion analysis laboratory. Patients or Other Participants: 23 junior varsity female lacrosse and soccer players. Intervention(s): Independent variables were group (core stability, plyometric, control) and time (pre-test, post-test). Subjects performed five trials of a DVJ prior to and after completion of a four week period during which intervention subjects engaged in a core stability or plyometric program. Main Outcome Measures: Dependent variables were 3-dimensional hip, knee, and trunk kinetics and kinematics during the landing phase of a DVJ. Group means and associated 95% confidence intervals were calculated via bootstrapping across the entire landing phase. Curve analysis using an alpha level of P<0.05 was performed to identify time periods where the confidence interval bands for the groups did not cross. Results: Significant within group differences were shown for lower extremity kinematic and kinetic variables for both intervention groups. No differences were shown for trunk kinematics. The control group had a decrease in knee external rotation moment. The plyometric group had a decrease in knee flexion and knee internal rotation angles in addition to a decrease in knee flexion and knee valgus moments. The plyometric group also had an increase in knee valgus angle and knee external rotation moment at the end of landing phase. The core stability group had decreases in hip internal rotation and knee flexion angles while also increasing the knee internal rotation angle. There were several kinetic changes including a decrease in hip flexion and internal rotation moments as well as an increase in hip abduction moment. Finally there was a decrease in the knee valgus moment. All significant kinetic changes had a strong effect size. Conclusions: An in-season, four week training program at the junior varsity level for female athletes resulted in significant changes in kinematic and kinetic findings related to increased ACL injury risk. The plyometric group was limited to changes found only at the knee joint while the core stability group had alterations at the hip and knee joint. The results of this study suggest that both types of exercise are warranted in ACL injury prevention programs.