NICKOLS-RICHARDSON, S. M., C. M. MODLESKY, P. J. O'CONNOR, and R. D. LEWIS. Premenarcheal gymnasts possess higher bone mineral density than controls. Med. Sci. Sports Exerc., Vol. 32, No. 1, pp. 63-69, 2000.
Purpose: The purpose of this study was to examine bone mineral density (BMD), body composition, dietary intake, physical activity, and energy expenditure (EE) in premenarcheal gymnasts (N = 16; age = 10.5 ± 1.5 yr) in comparison to age- (± 0.35 yr), height- (± 2.6 cm), and weight- (± 1.5 kg) matched controls (N = 16; age = 10.5 ± 1.3 yr). It was hypothesized that premenarcheal gymnasts would have higher BMD, fat-free soft tissue (FFST) mass, physical activity, and EE, but lower fat mass, percent body fat, and dietary intake than controls.
Methods: Dual energy x-ray absorptiometry was used to measure whole body, femur, and lumbar spine (L1-4) BMD, FFST, and fat mass. Three-day diet records were used to estimate mean daily dietary energy, macronutrient, and calcium intakes. Physical activity and EE were estimated by the Seven-Day Physical Activity Recall.
Results: The BMD means of the gymnasts were significantly higher (P < 0.05) than controls at all sites, except whole body, as were lumbar spine and femoral neck bone mineral apparent densities, despite lower protein intake expressed per kg FFST mass. Fat mass was significantly lower in gymnasts versus controls (P < 0.01) as was percent body fat (P < 0.001). Very hard physical activity during weekdays (P < 0.0001) and estimated EE (P < 0.01) were significantly higher in gymnasts compared with controls.
Conclusion: Premenarcheal gymnasts have higher BMD than age-, height-, and weight-matched controls.
Women in their mid-30s who formerly competed in college gymnastics have higher bone mineral density (BMD) than women who never participated in artistic women's gymnastics (17). Female college gymnasts possess higher BMD compared with college-age female nonathletes (16,23,24). Moreover, college gymnasts exhibit high BMD despite menstrual cycle disruptions (16,28) as well as energy and calcium intakes below the Recommended Dietary Allowances (RDA) for their age group (16,23). These studies show that participation in competitive women's artistic gymnastics for a decade or longer is associated with the development of high BMD.
The exact reasons for high BMD in college age and older former college gymnasts are unclear. It seems unlikely that high BMD can be accounted for by higher nutrient intakes by gymnasts because there is evidence that gymnasts report lower calcium and total energy intake than comparison groups (16,23). Regular gymnastics training may increase BMD because these activities present the skeleton with high-impact mechanical loads. Alternatively, it is possible that individuals who either gravitate toward participation in gymnastics or those who are able to adhere to the rigorous training without a career-ending injury are genetically prone toward possessing either higher BMD or the biological mechanisms for higher BMD (16).
Because of the evidence of high BMD in young adult gymnasts, insight into the potential role of early gymnastics training on BMD can be obtained by studying child gymnasts who have neither trained for as many years as college gymnasts nor have experienced menarche. Accordingly, the purpose of the present investigation was to test whether premenarcheal female gymnasts possess higher BMD compared with age-, height-, and weight-matched nongymnast controls. Matching of gymnasts and controls was conducted to control for the influence of these variables on BMD as it has been shown that older, taller, and heavier children possess higher BMD compared with younger, shorter, and lighter children (32). Factors with potential relevance to BMD were also assessed, including body composition, dietary intake of energy, macronutrients, and calcium, physical activity, and energy expenditure (EE). It was hypothesized that premenarcheal gymnasts would have higher BMD, fat-free soft tissue (FFST) mass, physical activity, and EE, but lower fat mass, percent body fat, and dietary intakes than controls.