Evaluation Of A Urine Color Chart To Determine Hydration Status

Abstract

Body water balance is routinely challenged during exercise, particularly during exercise in the heat. Objective hydration assessment in athletes is essential for optimal performance and, more importantly, for prevention of heat injuries. Selection of an appropriate hydration assessment method is dependent on a number of variables, including cost, time, and required skill. Urine osmolality (U-OSMO) and urine specific gravity (USG) are valid and reliable indicators of hydration status under most conditions. However, U-OSMO and USG are laboratory tests which are costly and require time and technical skill. PURPOSE: The purpose of this study was to compare U-OSMO and USG to values determined using a Urine Color Chart (U-COL). METHODS: Urine samples were obtained from ten healthy, athletic, male subjects (age: 19.3 ± 1.25 yrs; height: 180.0 ± 7.77 cm; weight: 78.67 ± 9.17 kg; VO2max: 46.32 ± 4.47 mls/kg/min) under two conditions: EUHY, a well-hydrated condition and HYPOHY, under conditions of moderate (-3.96 % ± 0.63 body weight) hypohydration. U-OSMO was determined by freezing point depression (model 5002, Precision Instruments, Natick, MA); USG was determined by refractometry (model 5711-2021, Schuco International, London, UK). RESULTS: Results indicate high positive correlations between U-COL and known reliable indicators of hydration assessment, U-OSMO and USG: U-OSMO vs. U-COL (r = 0.847) and USG vs. U-COL (r = 0.737). CONCLUSION: The high positive correlations between U-COL and U-OSMO, as well as U-COL and USG indicate that U-COL is an accurate tool for hydration assessment in field settings. U-COL is not an appropriate tool, however, in laboratory and/or clinical settings where greater accuracy and precision is required. Because U-COL is simple, quick, and easy to administer, it is a very useful tool for increasing awareness of hydration assessment, especially in naïve populations.