Adaptations of bone to exercise are dependent in part on the magnitude and type of loading stimulus and the timing of the loading exposure across the life cycle. Women's artistic gymnastics and volleyball are Olympic disciplines practiced by millions worldwide, which are characterized by high impact loading (3-6 times the body weight) and muscle strength requirement. The aim of this study was to compare the effect of different impact loading sports on bone quality and body composition of pre-menarcheal girls. A total of 30 pre-pre-menarcheal athletes (aged 11.1±1.33[SD]y) participating in volleyball (n=10) and artistic gymnastics at high (HGYM, n=10) and low (LGYM, n=10) intensity training underwent total body DXA analysis. Output measurements were bone mineral content (BMC), areal bone mineral density (aBMD), fat free soft tissue mass (FFST), fat mass (FM), and percentage FM at the total body and regional level (arms, legs and trunk) as well as specific axial skeleton sites (thoracic and lumbar spine, pelvis). After adjusting for body size, total body composition measurements were all significantly (p<0.01) different in the three groups of pre- pubertal athletes. VOLLEY showed lower BMC and FFST, and greater FM and %FM vs. both HGYM and LGYM. The main difference between LGYM and HGYM was greater %FM in the former. Similar results were found at the regional level (but for similar BMC in the legs) and at lumbar spine and pelvis. Linear regression analysis showed that a model using FFST mass the as independent variable is able to explain more than 90% of variance in total body less head BMC in the whole group of impact loading athletes, whereas introducing %FM in the model did not improve it predictive power at all. The findings of this study provide evidence that greater bone mineral accrual takes place in pre-menarcheal impact loading athletes participating in artistic gymnastics vs. volleyball and the dose of impact loading activity mainly affect %FM; moreover, results suggest that BMC in the weight-bearing skeleton is strongly affected by FFST.
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