To analyze the association between body-fluid changes evaluated by bioimpedance vector analysis (BIVA) and dilution techniques over a competitive season in athletes.
Fifty-eight athletes of both sexes (men, age 18.7 ± 4.0 y; women, age 19.2 ± 6.0 y) engaging in different sports were evaluated at the beginning (Pre) and 6 mo after (Post) the competitive season. Deuterium dilution and bromide dilution were used as the criterion methods to assess total body water (TBW) and extracellular water (ECW), respectively; intracellular water (ICW) was calculated as TBW minus ECW. Bioelectrical resistance and reactance were obtained with a phase-sensitive 50-kHz bioelectrical impedance analysis device; BIVA was applied. Dual-energy X-ray absorptiometry was used to assess fat mass and fat-free mass. The athletes were empirically classified considering TBW change (Pre – Post, increase or decrease) according to sex.
Significant mean vector displacements in the Post groups were observed in both sexes. Specifically, reductions in vector length (Z/H) were associated with increases in TBW and ICW (r = –.718, P < .01; r = –.630, P < .01, respectively) and decreases in ECW:ICW ratio (r = .344, P < .05), even after adjusting for age, height, and sex. Phase-angle (PA) variations were positively associated with TBW and ICW (r = .458, P < .01; r = .564, P < .01, respectively) and negatively associated with ECW:ICW (r = –.436, P < .01). PA significantly increased in all the Post groups except in women in whom TBW decreased.
The results suggest that BIVA is a suitable method to obtain a qualitative indication of body-fluid changes during a competitive season in athletes.