Bone health among indoor female athletes and associated factors; a cross-sectional study.

This study aimed to compare the bone-mineral-density (BMD), vitamin-D (25(OH)D), serum-calcium and serum-phosphorus levels between female athletes engaged in weight-bearing and non-weight-bearing-sport, and to evaluate possible associations among studied variables. Study involved top-level female athletes (age: 16.9 ± 4.4 years) involved in non-weight-bearing- (swimming; n = 14)), and weight-bearing-sport (artistic gymnastic; n = 17). The variables included the BMD of left femoral neck (measured by dual-energy X-ray absorptiometry), 25-hydroxyvitamin D levels (25(OH)D), body height, body mass, body-mass-index, serum-phosphorus, and serum-calcium levels. Sufficiency for 25(OH)D (>75 nmol/L) was observed in 32.3% of the studied athletes (43% and 23% for swimmers and gymnasts, respectively). The studied athletes had appropriate BMD, with higher BMD in gymnasts compared to swimmers (1.24 ± 0.11 and 0.85 ± 0.09 g/cm2; t-test: 10.26, p < 0.01). Serum-phosphorus was higher in gymnasts (1.46 ± 0.17 and 1.27 ± 1.36 mmol/L, t-test: 2.78, p < 0.01. Serum-phosphorus levels were lower in athletes with 25(OH)D sufficiency (t-test: 2.31, p = 0.03). The 25(OH)D was not correlated to BMD (Pearson's r = -0.18, -0.14, -0.28, all p > 0.05, for total sample, gymnasts and swimmers, respectively). Although 25(OH)D was not correlated with BMD, in further investigations other assays of vitamin-D status (i.e. the bioavailability of the vitamin-D) should be included.