What is the strength of evidence supporting a relationship between osteoporosis and exercise?
The connection between osteoporosis and exercise is much more complicated than it would appear at first glance. The ultimate question is whether a lifetime of regular exercise reduces a woman's lifetime risk of osteoporotic fracture. A large, randomized, long-term trial with fracture as an endpoint would be very difficult and expensive. Studies of the relationship between exercise and osteoporosis suffer from many shortcomings:
- Many studies are observational (no intervention).
- Controlled trials are often not randomized (subjects are placed in groups by their willingness to do exercise).
- Studies are short term (6 weeks to 2 years).
- Sample sizes are small (and therefore lack statistical power).
- Most studies use BMD (an indirect measure) as an endpoint rather than fracture (a direct measure).
- Wide variation exists in the exercise intervention.
- The exercise intervention is often poorly defined (thus not reproducible) or is not applicable to clinical practice (e.g., "walking 50 minutes on a treadmill at 70 percent VO2 max").
- Types of exercise and skeletal sites measured vary widely across studies.
Despite these shortcomings, most studies show at least a trend toward improvement in such measures as falls, strength, and balance, as well as BMD. No randomized placebo-control trials of exercise in osteoporotic women using fracture as an endpoint have been published (1-3).
- National Osteoporosis Foundation. Physicians Guide to Prevention and Treatment of Osteoporosis. 2000.
- Gregg EW, Pereira MA, Caspersen CJ. Physical activity, falls, and fractures among older adults: A review of the epidemiologic evidence. J Am Geriatr Soc 2000; 48(8): 883-93.
- NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy. JAMA 2001; 285(6): 785-95.