Comparing Bioelectrical Impedance Analysis To Air Displacement Plethysmography For Body Composition Assessment In Female Athletes

Abstract

PURPOSE: To compare bioelectrical impedance analysis (BIA) and air displacement plethysmography (ADP) for body composition assessment in female collegiate athletes. METHODS: Retrospective review of body composition data for 61 NCAA female collegiate athletes (basketball n = 14, soccer n = 31, volleyball n = 16), measured by BIA and ADP on the same day. Paired t-tests, effect size using Cohen’s d, Pearson’s correlation, and Bland-Altman plots were used to compare percent body fat (%BF) and fat-free mass (FFM) measurements from BIA and ADP for the whole sample, and within sports. RESULTS: The sample included 61 female athletes ages 18-25 years (x̅ = 19.5 ± 1.4 years), with heights ranging from 160-190.5 cm (x̅ = 172.3 ± 8.9 cm), %BF measures ranging from 6.0-38.5% (x̅ = 21.3 ± 6.3%) for ADP and 13.4-36.0% for BIA (x̅ = 22.5 ± 4.7%) and FFM measures ranging from 36.2-69.3 kg (x̅ = 53.4 ± 6.8 kg) for ADP, and 38.8-63.8 kg for BIA (x̅ = 52.4 ± 5.8 kg). Overall, BIA and ADP had strong positive correlations for %BF (r = 0.67) and FFM (r = 0.891). BIA significantly underestimated FFM when compared to ADP (mean difference [MD] = -0.99 kg, p = 0.016, d = -0.32), while no significant difference was observed in %BF (MD = 1.17%, p = 0.056, d = 0.25). Linear regression on the Bland-Altman plots revealed small but significant negative trends for both %BF (β = -0.34, p = 0.004) and FFM (β = -0.166, p = 0.01) estimation by BIA in the total sample. This indicates possible proportional bias, in which BIA is more likely to overestimate %BF and FFM at low values, and underestimate %BF and FFM at high values. When comparing sports, BIA significantly overestimated %BF (MD = 5.42%, p = 0.001, d = 1.14) and underestimated FFM (MD = -3.71 kg, p = 0.001, d = -1.07) for basketball players and significantly underestimated %BF (MD = -2.06%, p = 0.04, d = -0.56) in volleyball players, when compared to ADP. No significant measurement differences were found in soccer players. CONCLUSIONS: BIA gives comparable body composition results to ADP for soccer players, but gives conflicting results regarding over and underestimation of %BF and FFM in basketball and volleyball players. Conflicting conclusions based on sport may indicate the need for specialized equations when extrapolating body composition measures using BIA for athletes at the higher and lower ends of the spectrum of %BF and FFM.