Summary

Following participation in the ACL prevention program preadolescent female athletes improved certain biomechanical risk factors associated with ACL injury.

Abstract

Anterior cruciate ligament (ACL) injuries are common and occur 2-9 times more often in females compared to males. The incidence of ACL injury increases from late childhood to adolescence, and children as young as 10 years old have demonstrated movement patterns associated with increased risk of ACL injury. Prevention programs have been shown to reduce injury rates, but the mechanism behind these programs is largely unknown. Furthermore, few studies have investigated biomechanical changes following prevention programs in children younger than 13 years old. The purpose of this study was to evaluate the effects of an internationally implemented injury prevention program, the F-MARC 11+, on risk factors for ACL injury in female preadolescent soccer players. We hypothesized that 1) the primary ACL risk factor, peak knee valgus moment, would improve following training, and 2) athletes classified as higher risk for injury would improve more than lower risk athletes. We also explored additional kinematic and kinetic variables that have been correlated with ACL injury.

Pre and post-season motion capture data were collected from forty-six female athletes aged ten to twelve years (Intervention: n=26, 11.8±0.8 years, Control: n=20, 11.2±0.6 years) performing pre-planned cutting (CUT), unanticipated cutting (UACUT), and double-leg jump (DLJ) tasks. In addition, athletes were categorized as being at “high-risk” or “low-risk” for ACL injury according to their pre-season score on the Landing Error Scoring System (LESS) test. The LESS is a valid and reliable clinical assessment tool for identifying improper movement patterns during a jump-landing task. The 50th percentile value from the pre-season scores for all subjects was used as the cutoff for being at high or low-risk. Athletes in the intervention group participated in 15 sessions of the F-MARC 11+ warm-up program 2x/week for 7-8 weeks during their season. Lower extremity joint angles and moments were evaluated using OpenSim, widely used biomechanics software, and the average pre-to-post change in each variable was calculated. Independent sample t-tests were used to test for differences in the mean change between control and intervention groups. Two-way ANOVA were used to test for significance between the intervention vs. control groups and high-risk vs low-risk groups. Post-hoc independent sample t-tests were performed to test for differences between high-risk and low-risk athletes within each group.

Athletes participating in the intervention program had significantly greater reductions in the peak knee valgus moment compared to the control group during DLJ (p=0.026). Compared to their low-risk counterparts, high-risk athletes in the intervention program saw greater improvement in knee valgus moment during CUT (p=0.013) and DLJ (p=0.019), and greater improvement in peak hip adduction moment during DLJ (p=0.021). Our investigation of additional variables associated with ACL injury, including peak hip adduction angle, peak knee flexion angle and moment, and peak knee valgus angle, did not reveal any significant improvement in intervention athletes over control athletes (p>0.05).

Following participation in the ACL prevention program preadolescent female athletes improved certain biomechanical risk factors associated with ACL injury. This study provides insights to the possible mechanisms behind the program’s success, particularly in those athletes at higher risk for injury.