Effects of physical activity/exercise on bone metabolism, bone mineral density and fragility fractures

Bone adapts its mass to mechanical stress from muscle contraction and ground reaction forces, with osteocytes playing a central role in transducing mechanical stimuli into biochemical signals that orchestrate bone modeling and remodeling. This suggests that there is a potential benefit to be derived from physical activity (PA)/exercise for preservation of bone mass. This article briefly reviews the existing literature on the effects of PA/exercise on bone metabolism, bone mineral density (BMD), and fragility fractures. Epidemiological studies have demonstrated an inverse relationship between PA level and fracture risk and its determinants, such as low BMD and falls. Conversely, prolonged disuse or unloading are associated with bone loss. Intervention studies have shown that PA/exercise is effective in increasing BMD and reducing fracture risk, with resistance, weight-bearing and high-impact exercise and high-intensity and high-frequency and intermittent training protocols found to provide the most marked effect. These findings support a role for exercise as a non-pharmacological, safe, and low-cost tool against bone loss associated with age and other conditions. However, high-quality studies are needed to establish the optimal exercise prescription. Furthermore, PA/exercise is effective in mitigating weight loss-induced bone loss and has the potential for reducing the increased fracture risk associated with preserved BMD that characterizes individuals with type 2 diabetes.