Objective: To determine the relationship between estimated cardiorespiratory fitness (CRF) and femoral neck (FN) bone mineral density (BMD) in men. Patients and Methods: This cross-sectional study included 2569 men aged 50 to 90 years (mean, 63.5 years) who had at least 1 health examination at a preventive medicine clinic between January 27, 1998, and February 24, 2015. Maximal treadmill tests were conducted using the Balke protocol and were used to estimate CRF. We stratified patients into low, moderate, and high CRF categories. The FN BMD was measured by dual-energy x-ray absorptiometry. Odds ratios (ORs) for T-scores of -2.5 or less (osteoporosis) and -1.0 or less (low BMD) were calculated for categorical CRF and were adjusted for weight, age, and days per week of resistance activity. Results: The sample prevalence of osteoporosis in the FN was 4.1% and of low BMD was 49.4%. There was a significant inverse association between higher CRF category and osteoporosis measured at the FN (moderate vs low: OR=0.34; 95% CI, 0.16-0.74; high vs low: OR=0.19; 95% CI, 0.09-0.42) and low BMD (moderate vs low: OR=0.64; 95% CI, 0.43-0.96; high vs low: OR=0.43; 95% CI, 0.29-0.65). Conclusion: In men, CRF is directly associated with BMD. These results suggest that moderate-to-high CRF levels attained through regular physical activity may attenuate age-related decline in BMD. Further studies are needed to determine whether this translates to a lower risk of osteoporotic fracture in more fit men.
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