The effect of exercise intensity on postmenopausal BMD: a meta-analysis

Abstract

Background: Previous reviews have concluded that exercise has only modest effects on aBMD in postmenopausal women. Despite the well-recognised strong positive relationship between load magnitude and bone response observed from animal research, the majority of human trials have examined the effects of only low to moderate intensity exercise on bone. We speculated that meta-analysing according to intensity may reveal a more potent exercise effect at higher intensity.Objectives: To determine the effects of low, moderate and high intensity exercise on aBMD at the spine and hip in postmenopausal women.Methods: Electronic databases and reference lists were searched for RCTs that examined the effect of exercise compared to control on DXA-derived lumbar spine, femoral neck or total hip aBMD in healthy postmenopausal women. Interventions were classified as low, moderate or high intensity and pooled based on classification. Mean differences (MD) were calculated using random effects models and a risk of bias analysis was undertaken.Results: Fifty-one trials, testing 61 interventions (17 low, 38 moderate, 5 high intensity) were included. At the lumbar spine, high intensity exercise yielded greater aBMD effects (MD = 0.025 g/cm2 95% CI [0.007, 0.043], p = 0.007) than moderate (MD = 0.013 g/cm2 95% CI [0.008, 0.018], p < 0.001) and low intensity (MD = 0.010 g/cm2 95% CI [0.005, 0.015], p < 0.001). Low and moderate intensity exercise was equally effective at the femoral neck (low: 0.012 g/cm2 95% CI [0.006, 0.017], p < 0.001; moderate: 0.011 g/cm2 95% CI [0.007, 0.016], p < 0.001), but no effect of high-intensity exercise was observed. Moderate intensity exercise increased total hip BMD (0.007 g/cm2 95% CI [0.003, 0.010], p < 0.001), but low intensity did not. There were insufficient data to meta-analyse the effect of high intensity exercise at the total hip. Risk of bias was mainly low or unclear due to insufficient information reported.Conclusion: High intensity exercise is a more effective stimulus for lumbar spine aBMD than low or moderate intensity, but not the femoral neck, however, the latter may be due to lack of power. While data from high-intensity exercise interventions are limited, the current comprehensive meta-analysis demonstrates the same positive relationship between load magnitude and bone response in humans as observed from animal research. Findings have implications for optimal exercise prescription for osteoporosis in postmenopausal women.