Determinants of Forearm Bone Mineral Density among Early Adolescents Female Gymnasts and Swimmers

Purpose: Bone mineral density (BMD) and bone mineral content (BMC) undergo significant changes during life. Amongathletes, skeletal health is one of the key elements determining the length and quality of a sports career.Methods: This study aims to identify and compare the key determinants of forearm BMD among early adolescent femalegymnasts (G), swimmers (S), and a non-training group (N), with a focus on training type, nutritional factors, fracture history,and anthropometric characteristics that may influence bone health during critical periods of growth and development. Itexamined 45 girls aged 10.70 ± .90 years. BMD and BMC of the forearm in the distal (dis) and proximal (prox) segments weremeasured by densitometry. Dairy consumption and eating habits were assessed by means of a nutritional interview. Basicsomatic measurements were carried out. Somatic maturation status, and puberty rate were determined.Results: All the analyzed bone parameters were significantly higher in group G compared to S and N (η2> .14; large effect;P< .001). Significantly more often, BMD below normal was recorded in groups S and N vs G. ANCOVA covariance analysiswas used to assess the strength of the relationship between forearm bone parameters and biological variables, nutritionalvariables, and physical activity. The results of covariance analyses showed that BMD dis was significantly influenced bysomatic maturation status, and physical activity (adj. R²= .65; P< .001). A Similar interaction was shown for BMC prox (adj.R²= .51; P< .001). BMD prox was significantly influenced by physical activity (adj. R²= .60; P< .001). A Similar interaction wasshown for BMC dis (adj. R²= .38; P< .01). Z-score was significantly influenced by dairy products (n/day) and physical activity(adj. R²= .54; P< .001).Conclusions: Physical activity, especially high-impact gymnastic training, turned out to be the strongest determinant of boneparameters of the forearm in girls.