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Schoenfeld, BJ, Nickerson, BS, Wilborn, CD, Urbina, SL, Hayward, SB, Krieger, J, Aragon, AA, and Tinsley, G. Comparison of multifrequency bioelectrical impedance vs. dual-energy x-ray absorptiometry for assessing body composition changes after participation in a 10-week resistance training program. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to assess the ability of multifrequency bioelectrical impedance analysis (MF-BIA) to determine alterations in total and segmental body composition across a 10-week resistance training (RT) program in comparison with the criterion reference dual-energy X-ray absorptiometry (DXA). Twenty-one young male volunteers (mean ± SD; age = 22.9 ± 3.0 years; height = 175.5 ± 5.9 cm; body mass = 82.9 ± 13.6 kg; body mass index = 26.9 ± 3.6) performed an RT program that included exercises for all major muscle groups. Body composition was assessed using both methods before and after the intervention; change scores were determined by subtracting pre-test values from post-test values for percent body fat ([INCREMENT]%BF), fat mass ([INCREMENT]FM), and fat-free mass ([INCREMENT]FFM). Mean changes were not significantly different when comparing MF-BIA with DXA for [INCREMENT]%BF (-1.05 vs. -1.28%), [INCREMENT]FM (-1.13 vs. -1.19 kg), and FFM (0.10 vs. 0.37 kg, respectively). Both methods showed strong agreement for [INCREMENT]%BF (r = 0.75; standard error of the estimate [SEE] = 1.15%), [INCREMENT]FM (r = 0.84; SEE 1.0 kg), and [INCREMENT]FFM (r = 0.71; SEE of 1.5 kg). The 2 methods were poor predictors of each other in regards to changes in segmental measurements. Our data indicate that MF-BIA is an acceptable alternative for tracking changes in FM and FFM during a combined diet and exercise program in young, athletic men, but segmental lean mass measurements must be interpreted with circumspection.

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The purpose of this study was twofold: 1) compare body volume (BV) estimated from dual energy X-ray absorptiometry (DXA) to BV from a criterion underwater weighing (UWW) with simultaneous residual lung volume (RLV), and 2) compare four-compartment (4C) model body fat percentage (BF%) values when deriving BV via DXA (4C) and UWW (4C) in physically active men and women. One hundred twenty-two adults (62 men and 60 women) who self-reported physical activity levels of at least 1,000 MET·min·wk volunteered to participate (age = 22 ± 5 years). DXA BV was determined with the recent equation from Smith-Ryan et al. while criterion BV was determined from UWW with simultaneous RLV. The mean BV values for DXA were not significant compared with UWW in women (p = .80; constant error [CE] = 0.0L), but were significantly higher in the entire sample and men (both p < .05; CE = 0.3 and 0.7L, respectively). The mean BF% values for 4C were not significant for women (p = .56; CE = -0.3%), but were significantly higher in the entire sample and men (both p < .05; CE = 0.9 and 2.0%, respectively). The standard error of estimate (SEE) ranged from 0.6-1.2L and 3.9-4.2% for BV and BF%, respectively, while the 95% limits of agreement (LOA) ranged from ±1.8-2.5L for BV and ±7.9-8.2% for BF%. 4C can be used for determining group mean BF% in physically active men and women. However, due to the SEEs and 95% LOAs, the current study recommends using UWW with simultaneous RLV for BV in a criterion 4C model when high individual accuracy is desired.