Weight-bearing exercise and markers of bone turnover in female athletes

Weight-bearing activity provides an osteogenic stimulus, while effects of s wimming on bone are unclear. We evaluated bone mineral density (BMD) and ma rkers of bone turnover in female athletes (n = 41, age 20.7 yr) comparing t hree impact groups, high impact (High, basketball and volleyball, n = 14), medium impact (Med, soccer and track, n = 13), and nonimpact (Non, swimming , n = 7), with sedentary age-matched controls (Con, n = 7). BMD was assesse d by dual-energy X-ray absorptiometry at the lumbar spine, femoral neck (FN ), Ward's triangle, and trochanter (TR); bone resorption estimated from uri nary cross-linked N-telopeptides (NTx); and bone formation determined from serum osteocalcin. Adjusted BMD (g/cm; covariates: body mass index, weight, and calcium and calorie intake) was greater at the FN and TR in the High g roup (1.27 +/- 0.03 and 1.05 +/- 0.03) than in the Non(1.05 +/- 0.04 and 0. 86 +/- 0.04) and Con (1.03 +/- 0.05 and 0.85 +/- 0.05) groups and greater a t the TR in the Med group (1.01 +/- 0.03) than in the Non (0.86 +/- 0.04) a nd Con (0.85 +/- 0.05) groups. Total body BMD was higher in the High group (4.9 +/- 0.12) than in the Med (4.5 +/- 0.12), Non (4.2 +/- 0.14), and Con 14.1 +/- 0.17) groups and greater in the Med group than in the Non and Con groups. Bone formation was lower in the Non group (19.8 +/- 2.6) than in th e High (30.6 +/- 3.0) and Med (32.9 +/- 1.9, P less than or equal to 0.05) groups. No differences in a marker of bone resorption (NTx) were noted. Thi s indicates that women who participate in impact sports such as volleyball and basketball had higher BMDs and bone formation values than female swimme rs.