Bone mineral content and body composition in postpubertal cyclist boys.

The effect of sports activity on bone mass was assessed by dual-energy X-ray absorptiometry in a group of 22 young cyclists aged 16.2 +/- 0.7 years. These athletes trained for 10 hours a week for over two years. Bone mass values were compared with those of 27 sedentary youngsters aged 16.9 +/- 0.3 years. There were no differences in total body bone mineral (TBBM) between groups. The leg bone mineral content (LBMC), body weight, and percentage fat were lower in the cyclists than in controls (p < 0.02, p < 0.01, and p < 0.001 respectively). No changes were observed when TBBM was normalized for weight. The changes observed earlier in LBMC disappeared when normalized for body weight. These results suggest that cycling does not stimulate bone mass in youngsters, and that the type, quality, and length of sports activity need to be defined.