We measure how your lower extremity, center of mass, and head move before, during, and at the end of the running training program. The running training includes a typical week of running for you plus 12 weeks of progressively increasing your mileage (13 weeks total). If you are enrolled in the study, you will be asked to come into the IU Biomechanics laboratory (Bloomington, IN) to perform a gait analysis to examine your running form at the start of the training program, after the 4^th week, and after the 12^th week of the training program. The gait analysis involves running over-ground in the lab and on a treadmill with sensors placed on your feet, legs, hips, and head. The treadmill run will simulate a normal run for you, in either time or miles. Following the visit to the lab for the baseline analysis, you will be given a foot pod and activity monitor to track your running mileage and general activity. You will be given a running training program to follow that has you performing your normal weekly running mileage for week 1 and then progressively increases your weekly running mileage using a periodization of three, 4-week cycles. For each cycle, your weekly mileage will be increased by 15% during the three “loading weeks” followed by a “recovery week” (i.e. 4^th week) for which your weekly mileage will be reduced by 20% relative to the third week. If you are in the control group, you will be asked not to change your normal weekly running mileage or running speed over the 13-week enrollment period. At the end of the 13^th week, you will return your foot pod and activity monitor and receive a gift card.