Mechanical Perturbation Training for ACL Injury Prevention

Overview

A prospective trial will be used to evaluate the efficacy of prophylactic mechanical perturbation training program. 24 female athletes who are regular participants in activities that involve cutting, pivoting, jumping, and lateral movements prior to injury who range in age from 15-30 year are eligible. Using a prospective risk stratification design, female athletes with knee abduction moment (KAM) \> 25.25 Nm from drop jump motion analysis will be classified as high KAM and will receive 12 sessions of mechanically-driven perturbation training and female athletes with KAM \< 25.25 Nm from drop jump motion analysis will be classified as normal KAM and only participate in baseline performance testing, followed 6 weeks later by another session of drop jump motion analysis and performance testing.

Anterior cruciate ligament (ACL) injuries are prevalent in sports with female athletes at particularly high risk. Female athletes have 2-4x higher risk of ACL injury compared to their male counterparts in the same high-risk sports. Modifiable and non-modifiable risk factors play a role in the high incidence of ACL injuries in female athletes. High knee abduction moment (KAM), is a known modifiable risk factor for ACL injury risk. Female athletes with a KAM greater than 25.25 Nm have been identified as at high risk for an ACL injury. The ability to classify female athletes who are at a high risk for an ACL injury, highlights the importance of identifying modifiable risk factors that can be readily addressed by physical therapists and developing targeted treatments to potentially reduce ACL injury risk while improving functional performance. Neuromuscular training programs are treatments designed to help improve coordination, strength, and control. Such training programs have been designed to alter biomechanical and neuromuscular measures, in particular high KAM, in order to improve performance and function and thereby reduce the risk of ACL injury. Neuromuscular training programs involving plyometric exercises can reduce dynamic lower extremity valgus and limb-to-limb asymmetries in healthy female athletes. Despite the reductions in injury rates seen with performance of neuromuscular training programs, incidence of ACL injuries is remains higher than acceptable. Novel training methods are currently in development to optimize these current ACL injury prevention programs. As unanticipated perturbations may contribute to ACL injury risk, incorporating a mechanical platform device that provides unanticipated surface compliance changes (i.e. the floor lowering down below a subject's feet) into an ACL injury prevention program has the potential to optimize knee biomechanics and neuromuscular performance, including during unanticipated perturbations. Mechanical perturbation has been advocated for as an effective training method to modify the sensorimotor system and restore normal neuromuscular coordination through exposing the subjects to controlled, progressive perturbations. Furthermore, mechanical perturbation has the potential to improve dynamic postural stability and control, and enhance muscle activation patterns. One advantage of mechanical perturbation devices is that they can be utilized while performing a variety of dynamic tasks such as hopping and jumping compared to static loading tasks such as standing and balancing activities. Dynamic tasks may place a greater demand on the knee joint, promoting joint stability as the subject overcomes the perturbation. Additionally, mechanical perturbation may allow physical therapists to administer random perturbations at different phases of the activities (i.e. as the subject is landing from a hop, or taking-off from a jump) that simulate real-life perturbations which occur during different functional or sporting activities. The goal of this study is to assess the effectiveness of an intensive neuromuscular training program to reduce risk factors associated with ACL injury