Effect of mode selection when using leg-to-leg BIA to estimate body fat in collegiate wrestlers.

AIM: When using leg-to-leg bioelectrical impedance analysis (LBIA) to examine body composition, a computer-programmed mode (i.e., standard STD or athletic ATH) must be selected prior to assessment. This study examined the effect of LBIA mode selection on the estimated %BF of collegiate wrestlers. METHODS: Forty hydrated (Usg <1.02) wrestlers had %BF estimated using the ATH mode, which was then compared to the STD mode and hydrostatic weighing (HW), used as the reference method. Mean difference from HW (MD), standard error of estimate (SEE), and pure error (PE) values were calculated for the entire sample and three data subsets according to body mass index (BMI, kg/m(2)): <25 (n=16), 25-29.9 (n=18), and >30 (n=6). RESULTS: The %BF (mean+/-SD) was underestimated by the ATH (12.1+/-4.7) and overestimated by the STD (17.1+/-5.2) mode when compared to HW (14.1+/-6.3) for the entire sample (P<0.05). When examined relative to BMI, the ATH mode accurately estimated %BF in the BMI <25 group (MD=-1.2%, SEE=2.7%, PE=2.8%) and the STD mode accurately estimated %BF in the BMI >30 group (MD=1.5%, SEE=2.4%, PE=2.8%). Both modes inaccurately assessed %BF in the BMI 25-29.9 group with predictive errors >3.5%BF. CONCLUSIONS: The ATH mode is not appropriate for all individuals meeting the definition of athletic. However, the predictive accuracy of LBIA may be improved by selecting the ATH mode when BMI <25 and the STD mode when BMI >30, even when testing athletes.

The effect of acute fluid consumption on measures of impedance and percent body fat using leg-to-leg bioelectrical impedance analysis.

OBJECTIVE: To examine the effect of acute fluid consumption on measures of impedance and percent body fat (%BF) using a common leg-to-leg bioelectrical impedance analyzer system. DESIGN: Cross-sectional design with treatment order determined using a counterbalanced assignment. SETTING: University laboratory. SUBJECTS: In total, 21 recreationally active men (mean age 19.7 +/- 1.0 years; body mass index 24.2 +/- 2.3 kg/m2) volunteered to participate in this study. INTERVENTION: Subjects had their body composition assessed on three separate occasions. After an initial baseline body composition measurement, subjects consumed 591 ml of water (H2O), a carbohydrate/electrolyte drink (CHOE), or received nothing, used as the control (CON). Subjects were reassessed 20, 40, and 60 min after baseline (POST). Urine specific gravity (USG) was recorded at baseline and 60 min POST to assess hydration state. RESULTS: There were no significant changes in impedance or total body water (TBW) for any of the measurement time periods after drinking H2O or a CHOE beverage. Body weight (BW) (P < 0.0001) and %BF (P < 0.02) increased significantly 20 min POST and remained elevated at the 40 and 60 min POST time periods. After drinking, USG significantly decreased (P<0.0001) 60 min POST from baseline. For the CON trial, there were no significant changes in BW, %BF, TBW, or USG over time. CONCLUSIONS: Fluid consumption had no effect on lower-body impedance despite causing significant changes in hydration state. A slight overestimation in %BF (approximately 0.5%) was observed due to increased BW in the H20 and CHOE trials. This finding may have little practical significance when assessing body composition by LBIA.