Body Fluid Redistribution Affects Dual-Energy X-Ray Absorptiometry Body Composition Scores

Dual-energy X-ray absorptiometry (DXA) is considered a gold standard for bone and body composition assessment. However, methodological factors might impact the validity and reliability of the recordings. The effect of exercise-induced body fluid changes on DXA body composition scores has not been systematically studied. PURPOSE: To determine DXA changes following exercise-induced body fluid redistribution in Hispanic males. METHODS: Participants (n = 30, age = 20.8 ± 3.8 yr., weight = 67.1 ± 12.0 kg, height = 170.6 ± 6.6 cm, BMI = 23.0 ± 3.9 kg·m2) randomly completed 30-min upper-body exercise (UBE) at 70% of heart rate reserve (HRR), 30-min lower-body exercise (LBE) at 70% HRR, and 30-min seated control (CTRL). Body composition was determined by DXA before and after the interventions. Repeated-measures 3x2 ANOVA studied interactions between experimental conditions and body composition variables. Reliability included the coefficient of variability (CV). RESULTS: Mean differences were found on UBE tissue fat (M = 0.35 ± 0.12%; p = 0.007), region fat (M = 0.32 ± 0.11%; p = 0.008), lean mass (M = 0.27 ± 0.01 kg; p ≤ 0.0001), and total mass (M = 0.27 ± 0.05 kg; p ≤ 0.0001). Mean tissue differences were found for the total body in the CTRL (M = 0.10 ± 0.04 kg; p = 0.008), UBE (M = 0.19 ± 0.03 kg; p ≤ 0.0001), and LBE (M = 0.31 ± 0.04 kg; p ≤ 0.0001) conditions. Reliability scores were high within experimental conditions (CV = 0.2% to 16.2%). Only 19% of the body composition variables showed CV ≥ 10%. CONCLUSION: Body fluid redistribution during exercise elicited small and consistent changes in DXA body composition scores in males.