A simple method to assess acute hydration status in humans has been recently proposed, but several question remain regarding its reliability, validity, and practicality.
PURPOSE: To establish the reliability of a simple method to assess euhydration, that is, to assess whether this method can be used as a consistent indicator of hydration status of a person. In addition, we sought to assess whether exercise has an effect on urine volume when euhydration is maintained and a standard volume of water is ingested.
METHODS: Five healthy, physically active men and five women, 22.5 ± 2.3 years old (mean ± standard deviation) reported to the laboratory after fasting for 10 hours or more on three occasions, separated by seven days. For the two identical resting conditions (EuA and EuB), they remained at rest in a seated position for 45 minutes. For the exercise (EuExer) condition, participants exercised intermittently in an environmental chamber (average temperature and relative humidity = 32 ± 3° C and 65 ± 7%, respectively) for a period of 45 minutes, drinking water to match sweat losses; the order of treatments was randomized. Upon finishing the treatment period, they ingested a volume of water equivalent to 1.43% BM in 30 minutes. Urine was collected henceforth every 30 minutes for 3 hours.
RESULTS: Urine volume was slightly higher for EuExer (1205 ± 399.5 mL) than for EuB (1072.2 ± 413.1 mL) (p= 0.049), but not different from EuA (1068 ± 382.87mLp = 0. 18); the two resting conditions were nearly identical (p= 1.0), and they were strongly correlated (r = 0.849, p = 0.001).
CONCLUSIONS: This method, besides simple, proved to be consistent in our measurements, so it can be used with the assurance that the measurements are valid and reliable.
