Estimation of body density in adolescent athletes.

Abstract

National samples of 141 male and 133 female highly-trained adolescent athletes were studied to derive anthropometric-based equations predicting body density. Anthropometric measures included skinfold thicknesses at seven sites, circumferences at 14 sites, and diameters at nine sites. Criterion measures of body density were determined by underwater weighing with corrections for residual lung volume based on the oxygen dilution method. Variable selection procedures included factor analysis followed by forward-stepping regression and polynomial analysis. For both the male and female samples, two quadratic equations utilizing either the sum of three or seven skinfold measures were derived. Within the male sample, high validity coefficients (R = 0.81 0.82) and low standard errors (SEE = 0.0055 0.0056 g-ml !) were shown with these equations. Similar results were demonstrated with the equations for females (R = 0.82 and SEE = 0.0060 g-ml~ l). Crossvalidation on independent samples of male (n = 66) and female (n = 46) adolescent athletes further confirmed these findings. In the cross-validation sample of males, predicted scores were highly correlated with actual body density (r = 0.86 0.87) and the total error of prediction ranged from 0.0057 to 0.0061 g-ml~ l. Among the females, these values were r = 0.82 0.83 and total error = 0.0058 to 0.0063 g*ml-1. These results indicate that within reasonable limits of error, the sum of three or seven skinfolds may be used to make estimates of the body density of adolescent male or female athletes. Appraisal of body composition can serve as a valuable aspect characterizing either the status of preparation for competitive athletic participation or the nature of biological variations differentiating athletes from other groups. There are a variety of techniques for such appraisal, but in many instances the use of anthropometric measures to estimate body composition serves as the only practical means available. However, while a large number of equations have been derived to relate measures of circumferences, diameters, and/or skinfold thicknesses into estimates of body density, relative fat, or other aspects of body composition, most have been found to be population-specific in nature (Flint et al. 1977; Katch and Michael, 1969; Lohman, 1981; Jackson and Pollock, 1977). In this regard, most equations are limited to estimation of characteristics in groups similar to the original derivation samples. A previous study of Center for Youth Fitness and Sports Research, University of Nebraska, .Lincoln, Nebraska 68588-0138 Human Biology, September 1984, Vol. 56, No. 3, pp. 439-448. © Wayne State University Press, 1984 This content downloaded from 157.55.39.116 on Sat, 11 Jun 2016 05:54:09 UTC All use subject to http://about.jstor.org/terms 440 William G. Thorland, et al. young athletes has shown that large errors in estimation of body density result when equations which were derived from general populations are applied to more highly conditioned subjects (Thorland et al. 1984). With the absence of any anthropometric technique designed to estimate the body density of adolescent participants of different sports, the present study was conducted to generate such new equations and to determine their cross-validity on other young athletes. Methods and Materials