Physical activity and exercise in the maintenance of the adult skeleton and the prevention of osteoporotic fractures
Physical activity and exercise are promoted as a nonpharmacological strategy to maintain or enhance musculoskeletal health in adults and prevent osteoporotic fracture. Less clear is the optimal mode, intensity, duration, and frequency of activity to achieve this objective. Although a substantial osteogenic response to appropriate mechanical loading is clearly evident in animal models and strongly supported from athlete cross-sectional and prospective studies, the results from exercise interventions in adults are less impressive with modest net benefits generally of 1% to 3% in bone mineral density (BMD) (g/cm 2 ) at the clinically relevant hip and spine following prolonged weight-bearing impact loading or moderate- to high-intensity resistance-based training. However, the benefits to bone strength may be far greater with site-specific redistribution of bone mineral and geometric alterations, which can significantly enhance whole bone strength. In addition, improvements in muscle strength, balance, and functional performance accrue from physical training, especially high-intensity resistance and high challenging balance training, which can assist in falls prevention. Consequently, multimodal programs predominantly comprising weight-bearing impact loading with progressive resistance exercise, in combination with challenging balance and agility activities, would appear the most beneficial to maintain/enhance bone mass and strength, improve muscle function and prevent falls, thereby reducing osteoporotic-related fracture risk.