Neuromuscular Control of the Hip, Pelvis, and Trunk During Running
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Patellofemoral pain syndrome (PFPS) is the most common injury in runners and has a significant female sex bias. Current evidence suggests that several proximal factors, including hip muscle strength, hip muscle activation, and hip kinematics during running, play a large role in the development of PFPS, particularly in females. However, the relationships between these variables are unclear. A better understanding of these relationships in both males and females could help clinicians develop targeted interventions for this syndrome. Thus, this dissertation is comprised of four studies aimed to better understand the relationships between these risk factors. The first study investigated whether there are any relationships between hip muscle strength and hip muscle activation during running. Overall, hip muscle strength and hip muscle activity during running do not appear to be strongly related. The second study used a multiple regression approach to look for predictors of hip adduction and hip internal rotation during running. Sex was a significant predictor in both models, and running speed, static subtalar inversion range of motion, and gluteus maximus amplitude were significant predictors in the hip adduction model. The third study examined the effect of decreasing hip abduction strength on running kinematics and hip muscle EMG. After the fatigue protocol, there were no changes in gluteus medius amplitude or timing, and no changes in hip kinematics during running. However, there were some changes in kinematics, particularly at the trunk, as well as differences in gluteus maximus and tensor fascia latae activation. Finally, the fourth study used an alternative biomechanical method called continuous relative phase (CRP) to investigate the effect of sex and decreasing hip abduction strength on CRP variability at the hip. Decreasing hip abduction strength increased frontal plane CRP variability from 20-40% of stance phase, primarily in females, and females demonstrated less CRP variability than males in the frontal plane and transverse planes. Overall, the results from this study improve our understanding of the relationships between hip strength, hip muscle activation, and hip kinematics during running in both males and females, which may have implications for knee injury rehabilitation strategies. This dissertation includes unpublished co-authored material.