The effects of progressive resistance training on bone density: a review. Med. Sci. Sports Exerc., Vol. 31, No. 1, pp. 25-30, 1999. 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 in the United States in people aged 50 yr and older. Physical activity, particularly weight-bearing exercise, is thought to provide the mechanical stimuli or "loading" important for the maintenance and improvement of bone health, whereas physical inactivity has been implicated in bone loss and its associated health costs. Both aerobic and resistance training exercise can provide weight-bearing stimulus to bone, yet research indicates that resistance training may have a more profound site specific effect than aerobic exercise. Over the past 10 years, nearly two dozen cross-sectional and longitudinal studies have shown a direct and positive relationship between the effects 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 duration of the exercise protocol, and the bone density measurement techniques used. High-intensity resistance training, in contrast to traditional pharmacological and nutritional approaches for improving bone health in older adults, has the added benefit of influencing multiple risk factors for osteoporosis including improved strength and balance and increased muscle mass.
Submitted for publication June 1997.
Accepted for publication February 1998.
The authors wish to express their gratitude to Andrea Nuernberger and Erin Gunselman for their help in researching the material for this manuscript.
Conflict of interest: This work has been supported by federal funds from the U.S. Department of Agriculture, and Agricultural Research Service Contract 53-3K06-5-10 and the Brookdale National Fellowship. The contents of this publication do not necessarily reflect the views or policies of the U.S. Department of Agriculture or the American College of Sports Medicine, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government or the American College of Sports Medicine. The authors have no professional relationships with companies or manufacturers that will benefit from the results of the present manuscript.
Address for correspondence: Jennifer E. Layne, M.S., NEPS Laboratory, JM-USDA-HNRCA, 711 Washington Street, Boston, MA 02111.
Nutrition, Exercise Physiology and Sarcopenia Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111