A 1-year prospective study on the relationship between physical activity, markers of bone metabolism, and bone acquisition in peripubertal girls

We conducted a 1-yr prospective study to evaluate the association between physical activity and biochemical markers of bone formation and resorption with bone mineral acquisition in 155 peripubertal Caucasian girls (51 gymnasts, 50 runners, and 54 nonathletic controls). The bone mineral density (BMD) of the femoral neck, the greater trochanter, and the lumbar spine were measured by dual energy x-ray absorptiometry. Serum biochemical markers of bone formation (osteocalcin, bone-specific alkaline phosphatase, amino-terminal propeptide of type I procollagen) and bone resorption (degradation product of C-terminal telopeptide of type I collagen) were measured. The 1-yr increase in BMD (adjusted for age, height, Tanner stage, BMD at baseline, and increases in height and weight) of the femoral neck was 0.037 g/cm2 x yr [95% confidence interval (CI), 0.019-0.051 g/cm2 x yr), and that of the greater trochanter was 0.020 g/cm2 x yr (95% CI, 0.003-0.039 g/cm2 x yr) greater in gymnasts than in controls. The corresponding figures for gymnasts compared with runners were 0.038 g/cm2 x yr (95% CI, 0.009-0.041 g/cm2 x yr) and 0.033 g/cm2 x yr (95% CI, 0.006 to 0.043 g/cm2 x yr). The figures for the lumbar spine did not differ significantly between study groups. The baseline serum concentrations of formation markers and resorption marker accounted for 2.3-12.8% (P < 0.05) of the variation in the 1-yr increase in BMD at the femoral neck and lumbar spine. However, there was no significant difference between the levels of adjusted baseline bone turnover markers of the gymnasts, runners, and controls. The present data add considerable support to the argument that high impact mechanical loading is extremely important and beneficial for the acquisition of BMD of the hip during peripubertal years. Our results indicate also that a high rate of bone turnover, reflected as elevated bone markers, is only weakly associated with the 1-yr bone gain in peripubertal girls.