This summary of a Cochrane review presents what we know from research about the effect of exercise on bone mass in postmenopausal women.
The review shows that for postmenopausal women
- Exercise will improve bone mineral density slightly.
- Exercise will reduce the chances of having a fracture slightly.
These results might have happened by chance.
What is osteoporosis and exercise
Bone is a living, growing part of your body. Throughout your lifetime, new bone cells grow and old bone cells break down to make room for the new, stronger bone. When you have osteoporosis, the old bone breaks down faster than the new bone can replace it. As this happens, the bones lose minerals (such as calcium). This makes bones weaker and more likely to break even after a minor injury, like a little bump or fall.
Exercise interventions are typically those that stress or mechanically load bones (when bones support the weight of the body or when movement is resisted for example when using weights) and include aerobics, strength training, walking and tai chi.
Best estimate of what happens to postmenopausal women who exercise
Bone mineral density at the spine
People who exercised had on average 0.85% less bone loss than those who didn't exercise.
People who engaged in combinations of exercise types had on average 3.2% less bone loss than those who did not exercise.
Bone mineral density at the hip
People who exercised had on average 1.03% less bone loss than those who didn't exercise.
People who exercised by strength training had on average 1.03% less bone loss.
4 less women out of 100 who did exercise had a fracture. (Absolute difference 4%).
7 women out of 100 who exercised had a fracture.
11 women out of 100 who did not exercise had a fracture.
Our results suggest a relatively small statistically significant, but possibly important, effect of exercise on bone density compared with control groups. Exercise has the potential to be a safe and effective way to avert bone loss in postmenopausal women.
Osteoporosis is a condition resulting in an increased risk of skeletal fractures due to a reduction in the density of bone tissue. Treatment of osteoporosis typically involves the use of pharmacological agents. In general it is thought that disuse (prolonged periods of inactivity) and unloading of the skeleton promotes reduced bone mass, whereas mechanical loading through exercise increases bone mass.
To examine the effectiveness of exercise interventions in preventing bone loss and fractures in postmenopausal women.
During the update of this review we updated the original search strategy by searching up to December 2010 the following electronic databases: the Cochrane Musculoskeletal Group's Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2010 Issue 12); MEDLINE; EMBASE; HealthSTAR; Sports Discus; CINAHL; PEDro; Web of Science; Controlled Clinical Trials; and AMED. We attempted to identify other studies by contacting experts, searching reference lists and searching trial registers.
All randomised controlled trials (RCTs) that met our predetermined inclusion criteria.
Pairs of members of the review team extracted the data and assessed trial quality using predetermined forms. For dichotomous outcomes (fractures), we calculated risk ratios (RRs) using a fixed-effect model. For continuous data, we calculated mean differences (MDs) of the percentage change from baseline. Where heterogeneity existed (determined by the I2 statistic), we used a random-effects model.
Forty-three RCTs (27 new in this update) with 4320 participants met the inclusion criteria. The most effective type of exercise intervention on bone mineral density (BMD) for the neck of femur appears to be non-weight bearing high force exercise such as progressive resistance strength training for the lower limbs (MD 1.03; 95% confidence interval (CI) 0.24 to 1.82). The most effective intervention for BMD at the spine was combination exercise programmes (MD 3.22; 95% CI 1.80 to 4.64) compared with control groups. Fractures and falls were reported as adverse events in some studies. There was no effect on numbers of fractures (odds ratio (OR) 0.61; 95% CI 0.23 to 1.64). Overall, the quality of the reporting of studies in the meta-analyses was low, in particular in the areas of sequence generation, allocation concealment, blinding and loss to follow-up.