Abstract
Background. The anterior cruciate ligament (ACL) has been reported as one of the most commonly injured ligaments of the knee. Due to the prevalence of ACL injuries, treatment costs and post-injury complications, there has been a sustained research interest in this topic. One line of inquiry has been an investigation of the role that hip muscles plays in lower extremity alignment and the ability to use this information to provide evidence based practices in clinical rehabilitation. Objective. The purpose of this study was to determine the relationship between the neuromuscular activation of the hip with frontal plane motion at the knee joint while performing a single-leg squat exercise. Methods. A descriptive non-experimental design was employed, with a convenience sampling method to recruit 30 healthy college students (14 men, 16 women) over the age of 18 within an exercise science program. Participants performed 5 self-controlled single-leg squats on their dominant leg (3 left, 27 right). The joint kinematics of the lower extremity and EMG activity in 5 muscles of interest (gluteus maximus, gluteus medius, biceps femoris, vastus lateral is and adductor longus) were assessed. Results. A regression analysis was used to examine the relationship between the normalized electromyography signal and maximum knee valgus. P values of <0.05 were considered statistically significant. The regression equation demonstrated an inverse relationship between the EMG activity in the gluteus medius and adductor longus muscles and knee valgus. The regression coefficients were statistically significant with P values of 0.033 and 0.032 respectively. Conclusion. Based on the results, a statistically significant relationship was demonstrated when examining the activation of hip-stabilizing muscles and the amount of frontal plane motion occurring at the knee joint. As the activation of the gluteus medius and adductor longus decreased, the amount of knee valgus increased during a single-leg squat exercise. As physical therapy relies heavily on evidence based practice, identifying relationships between muscular activation patterns and undesirable movements or joint positions during functional exercises can enhance lower extremity injury prevention programs and provide more efficient rehabilitation programs.