Biomechanical and Neuromuscular Changes in Jump Landings Due to Short or Long Term Ankle Bracing and Fatigue

Abstract

<p>In order to prevent ankle sprain, prophylactic ankle bracing is common practice for many sports. The purpose of this dissertation was to investigate changes in loading and neuromuscular activation at the knee and at the hip when the ankle is braced. Additionally, fatigue is a known risk factor for both ankle sprain and anterior cruciate ligament (ACL) tear at the knee. The first two studies examined whether or not there was an interaction between the ankle brace and fatigue. Unwanted adaptation to long term bracing is also a concern. Thus, the third study addressed the question, does long term prophylactic ankle bracing change loading at the knee and hip? Furthermore, jump direction was specifically explored as a factor affecting loading of the hip and knee. Eight video cameras tracked jumping movements, two force platforms measured ground reaction forces, and a wireless electromyography (EMG) system detected muscle electrical activity. Knee and hip joint moments, loading rates, and joint moment impulses were used as kinetic dependent variables. EMG was used to quantify muscle activation as a percentage of maximum voluntary contraction for the vastus lateralis, biceps femoris, and gluteus maximus.</p> <p>Synthesizing the results of the three studies, the most significant findings were the differences in jump direction. They present a consistent picture of what would appear to be a more forceful jump in the forward direction and a more tentative jump in the backward direction. Fatigue did not interact with the braces, nor did it significantly affect the kinetics of the landings. However, it did have an effect on the activation of gluteal muscles, which may indicate a need to train those muscles in order to prevent injury. Results of the first and third studies do not indicate increased loading at the knee as an immediate effect of the ankle brace. Increased hip extension moment and hip extension moment impulse for the habitual bracers in the third study may indicate a proximal shift of shock absorption may be due to long-term bracing, or due to increased athleticism of the habitual brace group, which consisted of an NCAA division one volleyball team.</p>