Student Athletes Have A More Favorable Body Composition And Bone Mineral Density Than Non-athletes

PURPOSE Data on the relative contribution of planned exercise to body composition and BMD of premenopausal black and white African women is scarce. METHODS: Volunteer black and white University female students were recruited into groups according to exercise and race, namely white athletes (WA, n=117) and black athletes (BA, n=50), doing ≥5h/wk of planned weight bearing exercise, as well as white non-athletes (WNA, n=44) and black non-athletes (BNA, n=44) doing ≤1h/wk of planned exercise. Students with a body mass index (BMI) less than 28.0 and not pregnant were included. Exclusion criteria were use of corticosteroids/thiazides for ≥ 6 months and any known bone disease. Alpine spine (APS), femoral neck (FN), total hip (TH), and whole body (WB) BMD as well as body composition were measured with dual energy X-ray absorptiometry. RESULTS: Mean age, weight, height, and BMI for the total group were 20.3±1.8yrs, 60.7±8.6kg, 1.65±0.1m, and 22.1±2.3kg/m2. WA were younger and heavier than both BNA and BA (p less than 0.05). Height differed significantly between all groups with WA the tallest and BNA the shortest [median = 1.67(1.64-1.72)m vs. 1.59(1.54-1.64)m, p less than 0.05]. After adjusting for age and weight BMD were similar between WNA and BNA, as well as WA and BA. WNA had lower BMD at all sites compared to WA (p less than 0.001). BNA had lower BMD at all sites compared to BA [APS= 0.969(0.912-1.028) vs. 1.087(0.991-1.148)g/cm2; FN=0.821(0.773-0.904) vs. 0.951(0.888-1.028)g/cm2; TH=0.926(0.872-1.012) vs. 1.028(0.959-1.099)g/cm2; and WB=1.072(1.003- 1.108) vs. 1.129(1.074-1.180)g/cm2; p less than 0.001)]. Body fat percentage (BF%) was similar between WNA and BNA as well as WA and BA. WNA had significantly higher BF% than WA, and BNA than BA (p less than 0.05). Fat-free mass was similar between WNA and BNA, but lower in BNA compared to both WA and BA [38.3(33.5-42.0)kg vs. 46.4(43.3-49.1)kg and 42.3(39.9-46.7)kg, p less than 0.001). 36.4% WNA and 31.8% BNA had a Z-score between -1.0 and -2.0 at one or more BMD sites compared to 7.7% WA and 10% BA. Positive correlations were found between fat-free mass and height (r=0.7), weight (r=0.8), APS, FN, TH, and WB BMD (r=0.5 for all, p less than 0.05). CONCLUSIONS: Exercise seemed to be the main contributing factor towards a higher BMD and a healthier body composition amongst this group of female students; ethnicity did not seem to play a role