In the United States alone, approximately 16.4 million people participate in running activities. Unfortunately, up to 79% of these runners are injured each year. One more serious type of injury runners sustain is a tibial stress fracture, which is an injury that requires 6-8 weeks of rest. These injuries also have an alarmingly high 36% re-injury rate. Excessive vertical loading, such as load rates and tibial shock, has been linked to an increased risk of tibial stress fractures. Many runners exhibit excessive vertical loading bilaterally. Furthermore, torsional loading, quantified by the free moment, has been also implicated in tibial stress fracture development. Although both of these risk factors involve external loading, stress fractures occur due to loading at the bony level. Gait retraining to decrease vertical loading has been effective at decreasing these loads on the trained limb that received feedback. However, the impact of gait retraining on other risk factors such as free moment, contralateral limb loading, and the bony loading along the entire region where stress fractures are most common is unknown. Therefore, this dissertation consisted of three aims to examine changes following gait retraining with respect to each of these areas.

The purpose of Aim 1 was to identify if runners who have high vertical and torsional loads can decrease those torsional loads through gait retraining to decrease vertical loading. We hypothesized that runners would decrease those loads following gait retraining. We further hypothesized that the decrease in torsional loading would be less than the decrease in vertical loading as the subjects were not receiving feedback on torsional loads. We collected data on twenty runners both pre and post gait retraining during overground running at 3.7 m/s. The gait retraining protocol consisted of eight sessions of real-time visual feedback during treadmill running at a self-selected speed. This feedback was from an accelerometer attached to the anterior-medial aspect of the subject’s tibia on their limb with higher loads. The results revealed that runners with high peak adduction free moments reduce this peak following gait retraining. The decrease in free moment was moderately correlated to the decrease in vertical loading. Furthermore, the subjects decreased their free moment to a lesser degree than their vertical loading.

The purpose of Aim 2 was to identify if reductions in vertical loading on the trained limb transfer to the contralateral, untrained limb. We hypothesized that runners would decrease vertical load rates and tibial shock on their trained and untrained, contralateral limb following gait retraining. We collected data on ten runners both pre and post gait retraining during treadmill running at 3.35 m/s and a self-selected speed. The gait retraining protocol consisted of eight sessions of real-time visual feedback during treadmill running at a self-selected speed. This feedback was from an accelerometer attached to the anterior-medial aspect of the subject’s tibia on their limb with higher loads. Runners significantly decreased vertical load rates and tibial shock following gait retraining on both limbs and both running speeds.

The purpose of Aim 3 was to identify if runners with high vertical loading decrease tibial strain rates from the midshaft to distal third following gait retraining. We hypothesized that runners would decrease tibial strain rates following gait retraining. Furthermore, we hypothesized that these tibial strain rate decreases would be proportional to the subject’s external, vertical loading decreases. We collected data on five runners both pre and post gait retraining during overground running at 3.7 m/s. The gait retraining protocol consisted of eight sessions of real-time visual feedback during treadmill running at a self-selected speed. This feedback was from an accelerometer attached to the anterior-medial aspect of the subject’s tibia on their limb with higher loads. The results were mixed as only 4/5 subjects demonstrated decreased tibial strain rates following gait retraining. These external loading decreases were similar in magnitude to the strain rate decreases for 2/5 subjects. Additional subjects should be studied to further validate these findings.