Determinants of Bone Outcomes in Adolescent Athletes at Baseline: The PRO-BONE Study

Purpose: The determinants of areal bone mineral density (aBMD) and hip geometry estimates in adolescent athletes are poorly understood. This study aimed to identify the determinants of aBMD and hip geometry estimates in adolescent male athletes. Methods: One hundred twenty-one men (13.1 +/- 0.1 yr) were measured: 41 swimmers, 37 footballers, 29 cyclists, and 14 controls. Dual energy X-ray absorptiometry measured aBMD at lumbar spine, femoral neck and total body. Hip structural analysis evaluated hip geometry estimates at the femoral neck. Multiple linear regression examined the contribution of the sports practised, stature, lean and fat mass, serum calcium and vitamin D, moderate to vigorous physical activity, vertical jump and cardiorespiratory fitness with aBMD and hip geometry estimates. Results: Region-specific lean mass was the strongest positive predictor of aBMD (beta = 0.614-0.931) and football participation was the next strongest predictor (beta = 0.304-0.579). Stature (beta = 0.235-0.380), fat mass (beta = 0.189), serum calcium (beta = 0.103), serum vitamin D (beta = 0.104-0.139), and vertical jump (beta = 0.146-0.203) were associated with aBMD across various specific sites. All hip geometry estimates were associated with lean mass (beta = 0.370 - 0.568) and stature (beta = 0.338-0.430). Football participation was associated with hip cross-sectional area (beta = 0.322) and moderate to vigorous physical activity (beta = 0.140-0.142). Cardiorespiratory fitness (beta = 0.183-0.207) was associated with section modulus and cross-sectional moment of inertia. Conclusions: Region-specific lean mass is the strongest determinant of aBMD and hip geometry estimates in adolescent male athletes. Football participation and stature were important determinants for aBMD and hip geometry estimates, whereas the contribution of the other predictors was site specific.