The effects of progressive resistance training on bone density: a review

Osteoporosis is a major public health problem that is characterized by low bone mass and increased susceptibility to fractures, primarily of the hip, spine, and wrist. It is estimated to cause 1.5 million fractures annually i n the United States in people aged 50 yr and older. Physical activity, part icularly weight-bearing exercise, is thought to provide the mechanical stim uli or "loading" important for the maintenance and improvement of bone heal th, whereas physical inactivity has been implicated in bone loss and its as sociated health costs. Both aerobic and resistance training exercise can pr ovide weight-bearing stimulus to bone, yet research indicates that resistan ce training may have a more profound site specific effect than aerobic exer cise. Over the past 10 years, nearly two dozen cross-sectional and longitud inal studies have shown a direct and positive relationship between the effe cts of resistance training and bone density. Conversely, a handful of other studies have reported little or no effect on bone density. However, these results may be partially attributable to the study design, intensity and du ration of the exercise protocol, and the bone density measurement technique s used. High-intensity resistance training, in contrast to traditional phar macological and nutritional approaches for improving bone health in older a dults, has the added benefit of influencing multiple risk factors for osteo porosis including improved strength and balance and increased muscle mass.