Jenna M. Burchfield, Matthew S. Ganio, Stavros A. Kavouras, FACSM, J. D. Adams1, Melina A. Gonzalez, & Christian B. Ridings; 1Human Performance Laboratory, Department of Health, Human Performance, and Recreation, University of Arkansas, Fayetteville, Arkansas

Despite the necessity of euhydration, an optimal, user-friendly, accurate hydration assessment technique fails to exist for the general population. PURPOSE: The purpose of this study was to investigate a new hydration assessment technique, which utilizes no equipment or technical expertise to administer. We hypothesized that the number of urine voids over a 24-hr time period correlates to hydration status. METHODS: Forty-seven healthy individuals (n=24 females) participated (age 22±4 years, body mass 76±17 kg, height 1.64±0.27 m, body fat 20.4±8.7%). Participants abstained from caffeine and alcohol during the experiment. Participants were educated on how to record diet, fluid intake, and void output measurements. For 24-hours participants voided at a normal urge into a standard medical-grade container. Participants indicated volume, time, and urge of each void. Ad libitum fluid and food intake also were recorded over the 24 hrs. Total 24-hr urine volume, osmolality, specific gravity (USG), and color were measured. Subjects were classified as euhydrated (USG≤1.020) or hypohydrated (USG>1.020) according to standard criteria. RESULTS: Euhydrated (n=41) versus dehydrated (n=6) individuals had more voids (6±2 versus 4±1, respectively, P=0.02), greater 24-hr urine volume (2007±863 versus 1193±434 ml, P<0.001), lower urine color (2±1 versus 4±1, P<0.001), lower USG (1.012±0.004 versus 1.023±0.003, P<0.001), and lower osmolality (431±143 versus 841±137 mOsm/kgH20, P<0.001). As hypothesized, void number moderately correlated to hydration status as identified by USG (r=0.37, P<0.001), and osmolality (r=0.38, P<0.001). CONCLUSION: Void number positively correlated with USG and urine osmolality. This indicates that individuals with higher void numbers are more hydrated than those with lower void numbers over a 24-hr time period. Using void number as a hydration biomarker could be an optimal technique for the general public to self-assess hydration, considering it is as simple as counting void numbers over a 24-hr period.

Funding provided by the University of Arkansas College of Education & Health Professions and the Office of Research & Economic Development.

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