Validity of bioelectrical impedance analysis to estimation fat-free mass in the army cadets

Abstract

Abstract: Background: Bioelectrical Impedance Analysis (BIA) is a fast, practical, non-invasive and frequently used method fat-free mass (FFM) estimation. The aims of this study were: to validate predictive equations of BIA to FFM estimation in Army cadets and to develop and validate a specific BIA equation for this population. Methods: A total of 396 males, Brazilian Army cadets, aged 17-24 years were included. It was used eight predictive BIA equations published and a specific equation in FFM estimation, and dual-energy X-ray absorptiometry (DXA) as a reference method. Student's t-test (for paired sample), linear regression analysis and Bland-Altman method were used to test the validity of BIA equations. Results: Predictive BIA equations showed significant differences in FFM compared to DXA (p<0.05) and large limits of agreement by Bland-Altman. Predictive BIA equations explained 68% to 88% of FFM variance. Specific BIA equation showed no significative differences in FFM, compared to DXA values. Conclusion: Published BIA predictive equations showed poor accuracy in this sample. The specific BIA equation, developed in this study, demonstrated validity for this sample, although should be used with caution in samples with large range of FFM. (AU)