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Sam R. Moore, Hannah E. Cabre, Amanda N. Gordon, Abbie E. Smith-Ryan, FACSM. University of North Carolina at Chapel Hill, Chapel Hill, NC.

BACKGROUND: Physical activity consisting of high mechanical stress has shown a positive relationship with bone mineral density (BMD) in female athletic populations. Menarche after the age of 12 can lead to lower fat mass and BMD into adulthood; the effect of delayed menarche on lean mass (LM) is unknown. The purpose of this study was to characterize and evaluate the relationship between age of menarche, BMD, and fat free mass index (FFMI), in Division I collegiate female gymnasts. METHODS: Twenty-two competitive Division I female gymnasts (Mean±Standard Deviation [SD]: Age: 19.1±1.2 yrs; Height: 161.5±6.3 cm; Weight: 61. 7±8.4 kg; FFMI: 18.3±1.2 kg/m 2) participated in a survey (North American Menopause Society Validated Questionnaire) to assess age of menarche and a whole body DXA scan (GE Lunar iDXA) to measure BMD and LM. BMD percentile was evaluated using National Health and Nutrition Examination Survey (NHANES). FFMI was calculated from DXA-derived LM and bone mineral content (BMC), FFMI (kg/m^ 2)= LM (kg)+ BMC (kg)/Height^ 2 (m^ 2). Bivariate correlations were used to analyze the trength of the relationship between menarche, BMD, FFMI, and BMD percentile. RESULTS: Age of menarche (15.4±1.5 yrs; range-13 to 19 yrs) was negatively associated with BMD (r=-0.045; p= 0.851) and BMD percentile (r=-0.435; p= 0.055), although neither were significant. There was no significant relationship between FFMI and age of menarche (r= 0.194 p= 0.412 …