Date of Graduation


Document Type


Degree Name

Bachelor of Science

Degree Level



Health, Human Performance and Recreation


Ganio, Matthew


Washington, Tyrone

Second Reader

Greene, Nicholas


Introduction: It is known that 24-h void number is a valid way to assess hydration status. However, no studies have examined if urinary frequency just during the waking hours (~18 h) is a valid indicator of hydration status. Purpose: This study was conducted in order to determine if void number during only the waking hours was a valid indicator of hydration status compared to total voids over a 24-hour period. Methods: The subjects in this study consisted of 14 males and 18 females 18-80 yrs old who were healthy and not currently taking any body fluid altering medications. This study consisted of three trials, one familiarization and two experimental. Subjects underwent one dehydrated trial in which fluid intake was limited to 500 mL per day and one hydrated trial in which fluid consumption was encouraged. The subjects were asked to collect all urinary voids in jugs at the moment of first urge. For each void, urgency, thirst, and time of day (making note of which voids occurring during the non-waking hours) were recorded on the side of the jug and the level was marked. Results: The number of voids in 24-h while euhydrated and dehydrated was (7 ± 3) and (4 ± 2), respectively. Counting only the waking hour void number yielded a similar void number for both euhydrated and dehydrated (7 ± 3) and (4 ± 2), relative to the 24-h void number (P > 0.05). The only factor that effected void number was hydration status (P2O and 1.012 ± .004, respectively. USG and OSM for the dehydrated trial was 878 ± 133 mOsm/kg H2O and 1.023 ± .003, respectively. Conclusions: It does not matter if an individual counts total number of voids over 24-h or just waking hour voids; there is only a difference in void number when comparing hydration status. This is important because it means that an individual can just count how many voids they have throughout the course of the day (i.e., waking) for an indicator of hydration status. In this study voiding ~7 times during the day was the average for those in a hydrated state, and ~4 for those in the dehydrated state.

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