Bone Density Comparisons in Male Competitive Road Cyclists and Untrained Controls

SMATHERS, A. M., M. G. BEMBEN, and D. A. BEMBEN. Bone Density Comparisons in Male Competitive Road Cyclists and Untrained Controls. Med. Sci. Sports Exerc., Vol. 41, No. 2. pp. 290-296, 2009. Low bone mineral density (BMD) has been documented in endurance-trained runners; however, the bone status of cyclists is unclear. Purpose: The purpose of this study was to compare total body, lumbar spine, and dual proximal femur BMD in male competitive road cyclists (n = 32) and in age- and body mass-matched controls (n = 30). Methods: The cyclists had an average of 9.4 yr of racing experience and trained 7-22 h.wk(-1). BMD was measured using dual energy x-ray absorptiometry (DXA; GE Lunar Prodigy, v. 6.70.021). Calcium intake was estimated from a food frequency questionnaire. Resting serum total and free testosterone levels were measured by RIA (Diagnostic Systems Laboratory). Results: There were no significant differences (P > 0.050) between the cyclists (CYC) and the controls (CON) for age, height, body mass, or testosterone levels. CYC had significantly (P < 0.050) lower percent body fat and higher bone-free lean body mass than the CON. Calcium intake for CYC was significantly higher (P < 0.050) than for the CON group (1557 +/- 132 vs 1098 +/- 69 mg.d(-1)). Anterior-posterior spine (L2-L4) and lateral spine (LS) BMD (g.cm(-2)) were significantly lower (P < 0.050) for CYC (L2-L4 = 1.165 +/- 0.023 g.cm(-2); LS = 0.781 +/- 0.025 g.cm(-2)) than for CON (L2-L4 = 1.246 +/- 0.028 g.cm(-2); LS = 0.911 +/- 0.027 g.cm(-2)). Based on t-scores (SD from the young adult reference population mean), 9% of CYC and 3% of CON were classified as osteoporotic, whereas 25%, and 10% of CYC and CON, respectively, were osteopenic. Conclusions: Our findings indicated that male cyclists had lower spine BMD than controls, which was not associated with group differences in testosterone. Future studies are needed to elucidate the underlying mechanisms for low bone mass in cyclists.