Body Composition And Bone Mineral Density Of Middle distance And Long-distance Elite Female Runners Do Not Differ

Abstract

PURPOSE The purpose of this study was to compare the body composition and bone mineral density of elite female middle-distance runners (MDR) and long distance runners (LDR) to determine if either group is at higher risk for musculoskeletal injury. METHODS Athletes studied were 23 LDR and 24 MDR elite level runners (NCAA Div. I or USATF National Championships participants). LDR athletes competed at distances from 5,000 m through the marathon, whereas MDR athletes competed at 800 m through 3,000 m. Over a several-year period, these runners were assessed in the Laboratory for Elite Athlete Performance at Georgia State University using a protocol approved by the University's IRB. Bone mineral density (BMD) was assessed via a full body scan using a LUNAR DPXL densitometer (DEXA), with total body, leg and spine BMDs derived from this scan. Body composition was assessed using both DEXA fat percentage and the fat percentage calculated from the total of 7 skinfold measurements applied to the Jackson, Pollock, and Ward formula (MSSE 12:175 182, 1980). From these data, ratios of total and lean body mass to bone density were calculated in the two groups of runners to further assess stress-fracture risk RESULTS Mean values ± SEE for the LDR and MDR groups were similar for height (165.7 ± 1.15 vs. 167.5 ± 0.66 cm), weight (53.3 ± 0.88 vs. 53.3 ± 0.78 kg), skinfold fat percentage (12.9 ± 0.31 vs. 12.5 ± 0.37), and DEXA fat percentage (13.2 ± 0.57 vs. 12.3 ± 0.59), but the LDR athletes were older (27.0 ± 0.87 vs. 24.6 ± 0.80 yr; P = 0.002). Also similar were mean values ± SEE (gm/cm2) for the LDR and MDR groups regarding total BMD (1.168 ± 0.014 vs 1.181 ± 0.009), spine BMD (1.109 ± 0.020 vs. 1.121 ± 0.018) and leg bone BMD (1.293 ± 0.019 vs. 1.318 ± 0.012). Stress fracture risk appears to be similar, as seen by nonsignificant differences between the LDR and MDR groups in the mean values ± SEE of total, leg, and spine BMD, and the ratios between lean body mass and total bone density (39.8 ± 0.68 vs. 39.5 ± 0.49), total body mass and total bone density 45.7 ± 0.82 vs. 45.1 ± 0.53), lean body mass and leg bone density (36.0 ± 0.64 vs. 35.4 ± 0.43), and total body mass and leg bone density (41.3 ± 0.77 vs. 40.5 ± 0.49). CONCLUSIONS Although the two groups of elite female distance runners train differently (more mileage, less intensity for LDR; the reverse for MDR), the net skeletal and body composition response to training is similar.