Is bioelectrical impedance spectroscopy accurate in estimating total body water and its compartments in elite...

Bioelectrical impedance spectroscopy (BIS) provides an affordable assessment of the body's various water compartments: total body water (TBW), extracellular water (ECW) and intracellular water (ICW). However, little is known of its validity in athletes.

To validate TBW, ECW and ICW by BIS in elite male and female Portuguese athletes using dilution techniques (i.e. deuterium and bromide dilution) as criterion methods.

Sixty-two athletes (18.5 ± 4.1 years) had TBW, ECW and ICW assessed by BIS during their respective pre-season.

BIS significantly under-estimated TBW by 1.0 ± 1.7 kg and ICW by 0.9 ± 1.9 kg in relation to the criterion methods, with no differences observed for ECW. The values for the concordance correlation coefficient were 0.98 for TBW and ECW and 0.95 for ICW. Bland-Altman analyses revealed no bias for the various water compartments, with the 95% confidence intervals ranging from - 4.8 to 2.6 kg for TBW, - 1.5 to 1.6 kg for ECW and - 4.5 to 2.7 kg for ICW.

Overall, these findings demonstrate the validity of BIS as a valid tool in the assessment of TBW and its compartments in both male and female athletes.