The Effects of Injury on Running Status and Gait Biomechanics

Over the past several decades, endurance running has grown steadily as a popular form of physical activity. Running is easily accessible, does not require expensive equipment, and can be performed without specific skill training. Individuals who run also experience health benefits like increased cardiovascular health and reduced risk of all-cause morbidity. Despite these benefits, running is also associated with high rates of musculoskeletal injury. Although researchers have attempted to identify injury risks and mitigate the incidence of running injury, there is still no consensus as to why runners become injured. Research has also attempted to identify biomechanical movement patterns that occur as a result of injury, though definitive causal relationships have not been established. Running injury research is further complicated by several factors related to research design. There are few longitudinal or prospective studies, thus there is little evidence to support the identification of causal relationships between proposed risk factors and the development of running injuries. Recruiting homogenous groups comprised of individuals with similar injury history, running experience, and training level is also difficult. Moreover, there is no universal definition of injury for researchers to utilize when recruiting injured populations. In addition to a lack of definitive causes and definitions of injury, the individual response to injury varies. While some runners may continue running while injured, others may alter their training or stop running completely. Running participation is also influenced by life events that are not related to the sport or the development of injury. Additionally, many runners do not seek medical care for all injuries, thus not all instances of pain are classified as an injury. These discrepancies may influence the reported injury rates in the literature. Therefore, there exists a need for longitudinal or prospective research studies which clearly define injury and consider the homogeneity of the groups of runners recruited. The overall purpose of this dissertation is to investigate how running injury may affect running status and biomechanical movement characteristics. To address this purpose, three studies were developed to determine: 1) how injury and running and history influences the individual response to injury; 2) how movement characteristics may be influenced by the development of injury over time; and 3) how injury status may influence gait mechanics. The purpose of study one was to analyze injury and running history among current and former runners. A survey was developed to assess injury incidence, consequences of injury such as time off, and reported injury diagnoses and treatments. 312 participants completed the survey. Most participants reported that they had experienced at least one running injury. Of those who reported no history of injury, about half reported that they had experienced pain while running. The most common location of pain was the foot, followed by the knee. All participants were also asked to report any specific injuries they had experienced, and 775 specific injuries were reported. The four most common injuries were iliotibial band syndrome, plantar fasciitis, strained thigh/hip muscle, and medial tibial stress syndrome. About 40% of participants continued to run with these injuries. The results of this study demonstrated that the response to any given injury varied by individual. Despite feeling pain while running, some individuals did not consider themselves injured, and many participants continued running while injured. This study also supports the notion that running injuries exist on a continuum of severity and that the individual response to injury is complex and determined by various factors. Study two aimed to assess the incidence of running injuries and investigate movement characteristics as they relate to injury development in Division-I cross-country athletes over a two-year period. While research on running injuries is common, there is a lack of definitive causal relationships between running injuries and gait mechanics. For this study, cross-country runners were evaluated at pre- and post-season each year with three-dimensional kinematic and kinetic gait analyses. Participants also provided data regarding injury occurrence via self-report questionnaires, while injury reports were obtained from the team’s athletic training staff. This study was approached as an exploratory study, thus various statistical analyses were utilized to determine if movement characteristics were influenced by injury status, injury location, or year. First, self-reported injury incidence rates were higher than medically-reported injury incidence rates. This further supports the notion that the method of reporting injuries is an important consideration when examining injury incidence rates. There were no statistically significant results in movement characteristics between groups, though these statistical results were accompanied by large effect sizes. Interestingly, the most common location of pain in this group of runners was the foot, which supports the findings of the first study. The results of the first two studies supported the development of the third study, which analyzed the effect of plantar fasciitis on movement characteristics. The study design included participants with current plantar fasciitis, resolved plantar fasciitis, and no history of plantar fasciitis. This group design was developed to better assess movement characteristics which may exist before, during, and after an injury. Additionally, the study was designed to investigate foot characteristics, thus the foot was analyzed using a multi-segment foot model. Participants in the current plantar fasciitis group exhibited foot characteristics during gait which were indicative of a lower, less rigid arch. Participants in the resolved plantar fasciitis group demonstrated foot characteristics during gait which were indicative of a higher, more rigid arch. These results are meaningful because there were no differences between groups in static measures of foot characteristics, yet during gait, foot mechanics differed. These findings highlight the importance of modeling the foot as a multi-segment structure, rather than a rigid segment. The results of this study support the hypothesis that the movement of the foot during gait may contribute to the development of plantar fasciitis and that runners who have plantar fasciitis move differently than runners with resolved plantar fasciitis