Physiological and biomechanical factors contributing to the hip adduction angle in female runners

Running is a popular form of exercise that is accompanied by many health benefits. However, running also comes with a risk of overuse injuries. Women have a higher risk for overuse injuries during running than men. A person's lower extremity biomechanics during running are thought to influence the likelihood for an overuse injury. In female runners, a large peak hip adduction angle is a risk factor for overuse injury. Some female runners have a larger peak hip adduction angle than others. The presence of a large peak hip adduction angle in a female runner may be due to physiological, biomechanical, or anatomical factors. Previously proposed physiological factors contributing to hip adduction during running include eccentric hip abductor muscle strength, and lower extremity neuromuscular control. A large peak hip adduction angle in female runners may be due to insufficient hip abductor muscle strength, poor lower extremity neuromuscular control, or a combination of both. Alternatively, a large peak hip adduction angle may simply be a component of a person's self-selected gait pattern. A large peak hip adduction angle may also be the result of biomechanical factors, specifically the frontal plane pelvis and thigh position at foot strike. Elevated hip adduction throughout the entire stance phase is commonly reported in female runners with a large peak hip adduction angle. The hip adduction angle is determined by the three-dimensional position of the thigh segment relative to the pelvis segment. At foot strike, the beginning of the stance phase, the frontal plane pelvis and/or thigh angles may predispose female runners to larger or smaller peak hip adduction angles. Therefore, the frontal plane pelvis and/or thigh angles at foot strike may be biomechanical factors contributing to the peak hip adduction angle during running. The underlying anatomy may also contribute to the peak hip adduction angle during running. Specifically, a greater hip width to thigh length ratio (relative hip width) may predispose a runner to larger peak hip adduction angles. Investigating the proposed physiological, biomechanical, and anatomical factors contributing to the peak hip adduction angle in female runners will increase understanding of this risk factor for overuse injuries. This proposal aims to 1) compare hip abductor muscle strength and hip neuromuscular control between female runners with a larger or smaller peak hip adduction angle; 2) compare relative hip width, and frontal plane pelvis and thigh angles at foot strike during running between female runners with a larger or smaller peak hip adduction angle; and 3) investigate the contribution of physiological, biomechanical, and anatomical factors to the peak hip adduction angle in female runners. I plan to recruit 60 female runners to participate in this study. During data collection, runners will undergo a three-dimensional running analysis, and tests to measure hip abductor muscle strength, and hip neuromuscular control. For analysis of the first two aims, participants will be sorted by their peak hip adduction angle during running into three equal groups. For aim one, hip abductor muscle strength and hip neuromuscular control will be compared between runners in the groups with the largest and the smallest peak hip adduction angles. For aim two, relative hip width, and frontal plane pelvis and thigh angle at foot strike will be compared between runners in the largest and smallest peak hip adduction angle groups. For the third aim, the contribution of variables measured in the preceding aims to the peak hip adduction angle will be determined using a multiple regression model and the data from all 60 runners. The findings from this study will advance understanding of the physiological, biomechanical, and anatomical factors related to the peak hip adduction angle in female runners. This advanced understanding will be useful for efforts to treat and prevent overuse injuries in female runners with a large peak hip adduction angle.