This study examined whether the predictive accuracy of agespecific bioelectrical impedance (BIA) equations was improved when estimated fat-free body (FFR,,,) was corrected for the influence of FFB size on whole body resistance (WBR) and residual errors of prediction for 152 women, ages 20-72 years. The criterion measure of FFB (FFBHU) was obtained from hydrostatic weighing at residual volume (RV). FFB,, was predicted from age-specific equations. Each subject's FFB,,, was then adjusted for the relationship between FFB and residual scores using the Lohman et al. (1990) correction factor (Lohman TG, Going SB, Hewitt MJ, Williams DP 11990 I Med. Sci. Sports Exerc. 22:S109 [abst,ract]): FFB,,*, = (mean FFB reference sample -FFB,,) x 0.18 + FFBLIIA. Sample reference means were 45.0, 45.3, and 38.8 kg, respectively, for women 20-29 years, 3 0 4 9 years, and 50-70 years of age. The predictive accuracy of the unadjusted (FFBBTA) and adjusted (FFR,,)
BIA estimates was analyzed for the total sample and each age group. For the total sample, r', standard error of estimate (SEE), and root mean square error (RMSE) were, respectively, 0.82,2.5 kg, and 2.5 kg for FFB,,.
Corresponding values for FFB, , were, respectively, 0.81, 2.5 kg, and 2.6 kg. Across age groups, r2s ranged from 0.66-0.88, and the SEES and RMSEs were between 2.0 kg-2.8 kg. The relationship between FFRII, and residual scores (ry,reJ was significant (P < 0.05) for all age groups. The ry,rea