The purpose of the present study was to evaluate the differences in the body composition estimate of highly trained male athletes by three different methods: dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and skinfold thickness measurement (SFT). METHODS: The study occurred during a non-intensive training period. The measurements were performed at the Human Physiology laboratory. Participants: forty-three male athletes (19 waterpolo, 9 judo, 15 karate) who exercised regularly at least three hours per day, six days per week. Measurements: DXA, BIA and SFT measurements of percentage fat mass (%FM) and the amount of fat-free mass (FFM) were performed. Statistical analyses: the different %FM estimates by the three methods were compared using a one-way ANOVA, with posthoc Bonferroni test when values were significantly different. The same test was used to compare FFM values. The coefficient of variation (CV%=100xSD/mean) was calculated for each methods. Methodological differences among the various methods were analysed with the method of Bland-Altman. RESULTS: ANOVA test showed significant differences among the three methods. In particular, DXA significantly (p<0.001) overestimated %FM (12.4+/-4.1%) and underestimate FFM (67.0+/-6.9 kg) respect to SFT (7.8+/-0.9 % and 71.0+/-8.2 kg) and BIA (9.9+/-1.4% and 69.4+/-7.9 kg). Also Bland-Altman comparison among the estimates indicated wide differences between methods. CONCLUSIONS: DXA provides different body composition estimates than those derived from skinfold thickness measurement and BIA, so that the methods should not be used interchangeably.
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