DETERMINING THE EFFECTS OF FATIGUE ON ANTERIOR KNEE LAXITY

There is a high incidence rate of ACL injuries in the United States, and it has been previously found that increasing anterior knee laxity (AKL) is a risk factor for ACL injuries. Therefore, this study aimed to examine if there is a relationship between muscular fatigue and AKL as the relationship is not currently well understood. The primary purpose was to examine how muscular fatigue influences AKL in the preferred kicking leg from baseline to post-warm-up and throughout a fatigue protocol that simulates game or practice situations. Additionally, the secondary purpose of the study was to investigate the impact of fatigue on vertical ground reaction forces and muscle activity in the quadriceps and hamstrings using electromyography. By recruiting recreationally active female young adults from the local community, the research sought to provide insights into how fatigue affects anterior knee laxity and exploratory vertical ground reaction forces and muscle activity variables, aiming to improve injury prevention and rehabilitation programs. The methodology included a dynamic warm-up, a fatigue protocol using the Yo-Yo Intermittent Recovery Test Level 1, jumping and cutting tasks, and measurements of AKL using a GNRB® arthrometer, aiming to improve our understanding of muscular fatigue as an injury mechanism for ACL injury and determine if there is a link between muscle fatigue and AKL. For the drop jump task, the peak loading and average loading rate significantly increased. The jump height from the countermovement jumps significantly decreased. For the drop cut task, the pre-activation vastus medialis median frequency significantly increased. Despite the fatigue protocol eliciting some significant changes, the study concludes that the fatigue protocol did not induce the level of muscular fatigue necessary to induce significant changes in AKL for all participants. Further research with tailored fatigue protocols that investigate intersubject variability in AKL, in terms of magnitude and type of responders, and its underlying causes is needed to better understand the dynamics between muscular fatigue, AKL, and ACL injury risk.