Introduction: Few studies report on validation of body composition changes using the four-compartment model (4C), and no such studies are available in strength training. Here we present such a validation study for the determination of body fat and fat-free mass changes in bodybuilders, who used exercise and androgenic-anabolic steroids.
Methods: The study was carried out with 27 male bodybuilders in a cross-sectional study. Fifteen of these subjects also participated in an intervention program where body composition changes were measured. The 4C model served as the gold standard. The alternative mechanistic methods were underwater weighing (uww), deuterium dilution (dil), three-compartment model incorporating total body water (3Cw), three-compartment model incorporating bone mineral content (3Cb), and descriptive methods, namely dual-energy x-ray absorptiometry (DXA), prediction equations based on body mass index (BMI), skinfold measurement, and bioimpedance analyses.
Results: From the cross-sectional study, it appeared that biases and errors of most mechanistic methods were small (maximal 0.5% BF and 3.4%BF, respectively; exception 3Cb model). The 3Cw model had the lowest error (0.9%BF). The descriptive methods had small biases (exception BMI) but relatively large errors (range: 5.5-8%). Results on body composition changes (intervention study) were comparable with the results from the cross-sectional study.
Conclusions: Using the 4C model as the standard for determination of body fat and fat-free mass, this study revealed that apart from the prediction equation based on BMI and the 3Cb model, all methods gave acceptable group mean values. When accurate measurements on body composition and/or body composition changes on an individual level are needed, only the 3Cw model could serve as an alternative for the 4C method.