Date of Award
Doctor of Philosophy (PhD)
Clinical and Translational Rehabilitation Health Sciences
About 52.3 million American run on a regular basis. Up to 79% of runners get injured every year and the rate of injury has not declined over the past decades. Females have twice the risk of developing a running related injury (RRI). Rate of loading (ROL), tibial impact shock (TIS), and low movement variability may contribute to the development of RRI. Not much is known, however, about the relationships between impact kinetics (i.e. ROL, TIS) and movement variability. In addition, there is a lack of understanding about the effects of sex and speed on the aforementioned RRI risk factors. Therefore, the purpose of this dissertation was to study the association between impact kinetics and movement variability, and to investigate the effects of sex and speed on biomechanical variables including ROL, TIS, movement variability and coordination patterns during running.Thirty-six healthy runners participated in study one and two. In study three, data from thirty-two of those runners were analyzed. Vertical ground reaction force, 3D motion-analysis of lower extremities joint angles, tibial vertical acceleration, and electromyography (EMG) of lower extremity muscles were collected at running speeds that represented subject’s long slow distance speed (LSD), LSD+15%, and LSD+30%. Movement variability and patterns of hip and knee joints were quantified by using the vector coding method. ROL and TIS, peak EMG of five lower extremity muscles were calculated. In study one, Pearson’s correlation coefficients were used to investigate the association between movement variability and patterns with ROL and TIS at LSD speeds. In study two, repeated measure ANOVAs were used to investigate the effect of sex and speed on EMG and impact forces. In study three, a self-organizing map (SOM) was used to investigate biomechanical coordination patterns during running at LSD and LSD+30%.The most notable results from this dissertation suggest that 1) movement variability and patterns of hip and knee joints are associated with impact kinetics, 2) females exhibit a greater increase in ROL as running speed increases, and 3) greater running speeds are associated with a general shift to a coordination strategy characterized by greater magnitudes of RRI risk factors.