Mechanisms Underlying ACL Injury-Prevention Training: The Brain-Behavior Relationship

Abstract

In an attempt to elucidate the biomechanical and neuromuscular risk factors associated with anterior cruciate ligament (ACL) injuries in female athletes, numerous authors have examined sex differences in the performance of athletic tasks. Such investigators have consistently reported that lower extremity mechanics differ between males and females. For example, females exhibit decreased knee and hip flexion and increased quadriceps muscle activation, knee valgus angles, and valgus moments when compared with males.1–8 Taken together, this biomechanical and neuromuscular profile is thought to place greater loads on the ACL. Although the reasons underlying the sex differences in the performance of athletic maneuvers are not fully understood, evidence suggests that differences in proximal control may play a contributory role. Our group9 has reported that females favor use of the knee extensors over the hip extensors to attenuate impact forces during a droplanding task (ie, higher knee-extensor moments relative to hip-extensor moments and greater energy absorbed at the knee in relation to the hip). In comparison, male athletes were shown to attenuate impact forces through more equal use of the knee and hip extensors.9 Theoretically, if the hip extensors do not contribute to control of the body’s center of mass during landing, females may compensate through an overreliance on their quadriceps (ie, knee stiffening), by absorbing impact in the frontal plane (ie, greater knee