Inter-Subject Variability in Ground Reaction Force - Walking Speed Relationship Is Related to Different Motion of the Center of Mass

Walking programs provide an attractive intervention to address the preservation of bone mass in the aging population. Research suggests one in three women and one in five men over 50 will experience fractures due to osteoporosis [1,2]. Bone is a mechanically modulated tissue and thus, training programs that prescribe physical activities that dynamically load the skeleton through either muscle contractions (strength training) or locomotion (walking/running) would be expected to have a positive influence on bone mineral density (BMD) preservation. However, attempts to implement activity programs in populations at risk for developing osteoporosis to accrue or simply preserve bone mass have had limited success [3] due to a variable response between subjects. It has been suggested that the failure of these programs to significantly influence bone mass or density may be due to individual differences in the loads generated by the prescribed exercise regimes and/or the knowledge of specific types, intensities and volumes needed for effective osteogenic exercise. Walking, a simple, common activity, presents an interesting opportunity to examine the potential for individual differences in the style of walking to explain the variability in individual results to training programs designed to preserve bone density.