Comparison of bone metabolism based on the different ages and competition levels of junior and high school female rhythmic gymnasts

PURPOSE This study was to clarify the effect of age and competition level by measuring bone metabolism markers and bone mineral density measurements of junior high school and high school female rhythmic gymnasts, who restrict their diets to maintain a low body weight, while routinely undertaking long hours of high-intensity exercise, comparing the gymnasts based on their elite/non-elite. METHODS The study investigated 7 junior high school and 12 high school female rhythmic gymnasts. For comparison by competition level, the 7 junior high school gymnasts were separated into 3 gymnasts who competed at national level (junior high school elite), and 4 gymnasts who did not compete at that level (junior high school non-elite), and the 12 high school gymnasts were separated into 7 gymnasts who competed at national level (high school elite) and 5 gymnasts who did not compete at that level (high school non-elite). The measurement items were bone mineral density, bone metabolism markers (undercarboxylated osteocalcin (ucOC), osteocalcin (OC), bone-specific alkaline phosphatase (BAP), calcium (Ca), inorganic phosphorus (P), alkaline phosphatase (ALP), parathyroid hormone (PTH), type 1 collagen cross-linked N-telopeptide (NTx)). We also surveyed the gymnasts' height, weight and nutrition. RESULTS In this study we found: 1) The high school gymnasts who competed at high-level rhythmic gymnastics had good results for bone metabolism markers and bone mineral density. 2) Elite high school gymnasts had restricted diets. 3) Nutritionally, their energy intake and carbohydrate intake was low, but their intake of protein, calcium, iron, vitamin D and vitamin K was good. CONCLUSION The results found that the elite gymnastics showed a higher bone density than the non-elite group that suggests the possibility of inhibiting bone formation in the bone metabolism.