Running has been a popular sport because of convenience and health benefits. Fatigue among recreational runners may alter running mechanics, thereby increasing the risk for injury. The purpose of this study was to evaluate changes in lower extremity biomechanics throughout a 3.1 mile (5K) run. Ten male and ten female participants wore reflective markers to capture contralateral pelvic drop, knee adduction, knee abduction, and hip adduction. Participants ran 3.1 miles (5K) on a treadmill at a self-determined pace. A two-way, repeated measures ANOVA was conducted to capture the within-subject data across time and between-subject comparing differences in gender. Females had significantly greater contralateral pelvic drop but it did not change over time. Knee abduction angles significantly declined over the five observations. Gender differences and effects of distance can alter the biomechanics in recreational runners. More research is needed to identify predisposing factors to the development of chronic running injuries.