Body composition analysis of female adolescent athletes: comparing six regression equations

This study investigated whether meaningful differences occurred when percentage body fat (%BF) values were estimated for female adolescent athletes using six different regression equations found in the two of which were age-adjusted. Skinfold thickness (SF) and bioelectrical impedance analysis (BIA) measurements were taken prior to training and > or = 2 h postprandial on 29 gymnasts and 25 speed skaters who competed at a minimum of a provincial level. Mean ages were similar (14.3 +/- 1.6 yr, mean +/- SD, vs 14.3 +/- 1.5 yr); however, the speed skaters were taller (162.2 +/- 8.2 cm vs 154.0 +/- 5.0 cm, P < 0.001) and heavier (58.5 +/- 9.5 kg vs 46.0 +/- 7.9 kg, P < 0.001). Analysis of variance of %BF revealed a significant effect of sport (F(1,52) = 39.3, P < 0.001), with gymnasts having lower values. There was also a significant effect of regression equation (F(5,260) = 147.8, P < 0.001), and post-hoc comparisons revealed significant differences between almost all equations. Calculated %BF values ranged from 21.0 +/- 7.7% to 28.1 +/- 3.9% for speed skaters and from 10.3 +/- 5.3% to 22.8 +/- 3.7% for gymnasts. For both sports, the age-adjusted equations for SF and BIA produced the lowest and the highest %BF values, respectively. Our results indicate the need for caution when using field techniques to estimate %BF of female adolescent athletes. We suggest that an appropriate technique and regression equation for use with this group is the Jackson and Pollock quadratic equation for skinfolds, using Lohman's age-adjusted specific constants to correct for lower density of fat-free mass in youths.