Validity of “Generalized” Equations for Body Composition Analysis in Women Athletes

Abstract

Equations by Jackson, Pollock, and Ward (1980) and by Durnin and Womersly (1974) for estimating body density (BD) from skinfolds (SF) purportedly overcome the criticism of “population specificity” by taking into account age and the curvilinear relationship between SFs and BD. Selected equations were validated on 79 women athletes against %fat and fat(kg) measured by underwater weighing. Equations by Sloan, Burt, and Blyth (1962), Wilmore and Behnke (1970), and Katch and McArdle (1973) were also evaluated to compare the newer equations to older ones. The mean estimate of %fat by one equation by Jackson et al. utilizing the sum of triceps, abdomen, suprailiac and thigh SF was the same as the true value (20.1%) and correlated .795 (SEE ± 3.27 total error 3.23). Regression analysis showed it to have acceptable accuracy over the range of sample values (10.3–34.0%). The Durnin-Womersly equations overestimated %fat by 3.9 to 4.4% and were not acceptable. For the older equations, the mean Sloan et al. estimate (20.8 %Fat) was not significantly different from the true value and correlated .779 (SEE ± 3.37 total error 3.47). Regression analysis showed it to overestimate fat in leaner subjects and to underestimate it in fatter ones, making it unacceptable. The Wilmore-Behnke equation overestimated %fat by 4.3%. Equations by Jackson et al., using the sum of triceps, suprailiac and thigh skinfolds, and by Katch and McArdle were shown to be acceptable if the ordinate values were adjusted (1.0994921 to 1.1074921 and 1.08347 to 1.09147 respectively) to account for the higher density of women athletes.