Bone parameters as well as ground reaction forces were measured in runners with and without a history of stress fracture. There were differences in tibial bending strength and cortical area between groups There were differences in mean peak vertical ground reaction forces between groups Bone strength relative to ground reaction force was lower in women with vs. without a history of stress fracture. Strength deficits in the mid-tibia, and altered ground reaction forces may predispose an individual to stress fracture