J. M. Kuta

Prediction of percent body fat in adult males using dual energy x-ray absorptiometry, skinfolds, and hydrostatic weighing.

The purpose of this study was to compare the prediction of percent body fat (%FAT) by dual energy x-ray absorptiometry (DXA), skinfolds (SF), and hydrostatic weighing (HW) in adult males. Subjects were 35 adult male Caucasians (mean +/- SD; age: 39.1 +/- 14.0 yr, height: 180.6 +/- 5.3 cm, weight: 81.0 +/- 11.1 kg). %FAT, determined by HW with residual volume determined via O2 dilution, served as the criterion. DXA %FAT was determined by the Norland XR-26 (XR-26) bone densitometer and by the SF equations of Jackson and Pollock (JP) (1978), and Lohman (LOH) (1981). Criterion referenced validation included analyzing mean (+/- SD) %FAT values using a one-way ANOVA for significance, comparison of mean differences (MD), correlations (r), standard error of estimates (SEE), and total errors (TE). Significant differences were found between means of each method. The r (0.91) and SEE (3.0 %FAT) for DXA compare favorably with the established SF methods of JP and LOH for predicting %FAT; however, DXA demonstrated the largest MD (3.9 %FAT) and TE (5.2 %FAT). Regression analysis yields HW = 0.79* DXA + 0.56. The results do not support earlier research that found no significant difference between HW and DXA %FAT in males. The study suggests the density of the fat-free body (DFFB) is not constant, and that the variation in bone mineral content affects the DFFB, which contributes to the differences between DXA and HW %FAT. We recommend further research to identify inconsistencies between manufacturers of DXA equipment in prediction of %FAT in males.

A comparison of methods to predict minimal weight in high school wrestlers.

The purpose of this study was to compare the accuracy of body fat determinations and subsequent calculation of minimal weight (MW) by dual energy x-ray absorptiometry (DEXA), bioelectrical impedance (BIA), near-infrared photospectometry (NIR), and anthropometry (LOHMAN). Necessitated by mandatory state minimal weight testing, the methods were cross-validated on 95 Wisconsin high school wrestlers (mean +/- SD; age: 15.1 +/- 1.2 yr, height: 170.4 +/- 7.1 cm, weight: 63.4 +/- 9.8 kg). MW, defined as fat-free body/0.93, determined by hydrostatic weighing (HW) and residual volume via O2 dilution, served as the criterion. The validity of the four selected MW predictions were evaluated against HW by examining mean differences (MD), standard deviation differences (SDD), correlations (r), standard error of estimate (SEE), and total errors (TE). Statistically significant differences were shown between the methods and the criterion by t-tests; however, these were clinically small in Lohman (0.6 kg) and BIA (0.9 kg). TE ranged from 2.25 kg (Lohman) to 6.03 kg (NIR). The results indicated that Lohman skinfold equation provided the most accurate prediction of MW, demonstrating the highest correlation (0.972), lowest MD (0.6 kg), lowest SEE (2.12 kg), and lowest TE (2.25 kg) of the methods evaluated.

Cross-Validation of Methods to Predict Body Fat in African-American and Caucasian Collegiate Football Players

Eight skinfold (SF) equations and bioelectrical impedance analysis (BIA) were cross-validated in 71 Division IA college football players. Criterion percent body fat (%FAT) was determined by hydrostatic weighing (HW) and computed from body density (BD) for African Americans (n = 28) and Caucasians (n = 43). Results were analyzed by method, with position and race effects examined simultaneously using a two-way ANOVA. Analysis included computation of mean difference (MD), correlation (r), standard error of estimate (SEE), and total error (TE). Skinfolds had MDs ranging from -1.8 to 2.9%, correlations from .85 to .93, SEEs from 2.3 to 3.2%, and TEs from 2.3 to 4.2%. Bioelectrical impedance analysis was significantly different from HW and yielded the highest MD (3.8%), lowest correlation (r = .78), highest SEE (3.9%), and highest TE (5.4%). The Jackson and Pollock (1978) SF equation provided the most valid prediction of HW-determined %FAT in a racially mixed sample of college football players, demonstrating the highest correlation, lowest SEE and TE, and an intercept and slope not significantly different than 0.0 and 1.0, respectively.