Total Body Water Estimations Using Bioimpedance in the Athletic Young Adults

Bioimpedance techniques have the ability to estimate total body water (TBW) using a single frequency prediction equation (BIA), using hundreds of frequencies in complex Cole models (BIS), as well as using multiple-frequencies and prediction equations (MFBIA). However, the ability of the above methods to estimate TBW in athletic populations has not been investigated. PURPOSE: Compare BIA, BIS, and MFBIA estimations in athletic males and females to a criterion deuterium oxide (D2O) TBW measurement. METHODS: Twenty-seven females and fifty-one males between the ages of 14 and 30 participated in the study (19.15 +/3.42yr, 66.50+/11.26kg, 172.94+/9.28cm). Subjects reported to the lab in a fasted and hydrated state and provided a urine sample before ingesting approximately 11 grams of D2O. Four hours later the subjects provided another urine sample for the calculation of TBW using a standard isotope dilution method. During the four hour equilibration period TBW was measured using BIA, MFBIA, and BIS in no particular order. RESULTS: For males, all methods produced nearly identical and high r values (0.869-0.878) as well as low standard error of the estimate (SEE) values (2.96-3.06 L) with BIA producing the only significant mean difference (2.66 L, p 0.05). For females, all methods produced similar and high r values (0.82-0.85) as well as nearly identical and low standard error of the estimate (SEE) values (1.31-1.42 L). BIS significantly (p = 0.041) under estimated TBW (0.793 L) while BIA (0.737 L) and MFBIA (1.27 L) significantly (p < 0.02) over estimated TBW compared to D2O. However, BIS and BIA mean difference, although significant, were less than 1 L. CONCLUSIONS: The added frequencies and complex Cole models of the BIS appeared to improve the validity of TBW estimations compared to D2O in athletic males and females ages 14-30 years. However, all methods demonstrated high r values and low SEE values and have the potential to accurately estimate TBW in the current population. However, based on the current results the BIS method used in the current study demonstrated the most valid estimations of TBW for athletic males and females compared to D2O.