Bioelectrical Impedance Vector Analysis (BIVA) for Assessment of Hydration Status: A Comparison Between Endurance and Strength University Athletes

Abstract

Background: Adequate hydration is essential for athletes specifically before and after training, during competitions and in extreme conditions. Hydration assessment is performed using a variety of tools, and the combination of several techniques is recommended to accurately measure water losses and gains that greatly impact athletes’ performance.

Aim: The aim of this study is to assess the validity of bioelectrical impedance vector analysis (BIVA) as a tool for measuring hydration status in endurance and strength athletes pre- and post- training by plotting vectors variation by gender and sport and comparing it to reference methods.

Methods: 148 athletes (n=64) endurance and (n=84) strength divided between (n=90) males: (n=54) strength, (n=36) endurance and (n=58) females: (n=29) strength, (n=29) endurance, were evaluated on one experimental day, pre and post training. Urine samples were collected in the morning, prior to and after training for analysis of color and specific gravity (USG). Body weight changes were measured, sweat rate was calculated, and bioelectrical impedance analysis was performed prior to and post training to track changes in bioelectrical variables (R = resistance; Xc = reactance; Z = impedance vector; and PA = phase angle). Reference ellipses were plotted using data of 200 healthy non-athletic individuals equally divided between males and females.

Results: A strong agreement was noted between raw bioelectrical values standardized for height: Xc/h, R/h and Z, PA with each of USG and sweat rate. (p>0.05) The sensitivity of classic BIVA in detecting minor changes in hydration status is confirmed both graphically and statistically. No significant difference was observed in urine specific gravity values at different timepoints. The distribution pattern of raw bioelectrical values before and after training did not significantly change in the studied groups of athletes. R/h and Z statistically significantly decreased post-training in both genders and sports types. Male athletes exhibited a specific BIA vector distribution in comparison with the reference population and were slightly more hydrated than female athletes.

Conclusion: Bioelectrical variables (R, Xc, Z, and PA) assessment is gaining significant attention for the purpose of monitoring hydration levels in both healthy and unwell individuals. The impact of hydration on sports performance is undeniable, necessitating the development of easy and practical monitoring methods to ensure athletes can consistently perform at their peak.