Seventy-two percent of all stress fractures in athletes come from running, which can cause an immediate cessation of training. Additionally, fifty percent of all stress fractures occur in the distal end of the tibia. One way to keep the athlete moving without slowing down the healing process is using an unloader treadmill (TM) in a rehabilitation setting. The purpose of this study was to investigate relationship between the level of body weight (BW) unloading in an Anti-Gravity Treadmill and tibial acceleration. Fifteen collegiate cross-country team runners (Gender: 9 males, 6 females; Age: 20.4 ± 2.4 years; Weight 60.1 ± 12.6 kg) were recruited for this study. Tibial acceleration was assessed through a skin-mounted accelerometer which was attached to the lower third of the tibialis. Results show no significant difference between mean peak tibial acceleration from a 100% BW to 60% BW conditions. There was a significant (p ≤ 0.05) difference from 100% BW to 60% BW in mean peak to peak accelerations, which is indicative of tibial stress. Additionally, significant differences were observed among stride rate and heart rate which decreased throughout all BW conditions which shows changes kinetic and metabolic demands. In order to effectively reduce tibial stress in runners, a runner would have to start at or below 60% of their BW. Tibial acceleration was not reduced due to the kinetic changes which occurred from a reduction in BW
