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THE EFFECT OF FLUID AVAILABILITY ON CONSUMED FLUID VOLUME AND PERCEPTUAL THIRST MEASURES DURING AEROBIC EXERCISE

Abstract

Shealyn G. Sullivan, Luke W. Dobbins, Rebecca R. Rogers, Tyler D. Williams, Mallory R. Marshall, Joseph A. Pederson, Christopher G. Ballmann, FACSM, Courteney L. Benjamin. Samford University, Homewood, AL.

BACKGROUND: Ad libitum fluid intake is a common hydration practice during exercise. Fluid availability is a factor thought to influence fluid intake. However, it is currently unknown if readily available fluid will impact fluid intake behavior and gastrointestinal (GI) issues that are often associated with increased fluid intake. PURPOSE: The purpose of this study was to determine if ad libitum verses periodic fluid intake influences water consumption and GI distress during exercise. METHODS: Male and female NCAA Cross Country athletes (n = 11; age = 20 ± 1 y) participated in this counterbalanced cross-over study. Each participant completed a moderate intensity 10-km run on two separate occasions. In one trial, participants had unlimited availability to fluid to consume ad libitum (AL). In the other trial, participants consumed fluid periodically at stations placed every 3.2 km (PER). Assurance of euhydration prior to each trial was confirmed via urine specific gravity (USG) and urine color. Subjective perceptions of thirst and gastric fullness were assessed pre- and post-exercise via Likert questioning and a visual analog scale, respectively. RESULTS: Participants started each trial euhydrated (AL = 1.009 USG ± 0.009; PER = 1.009 USG ± 0.009; urine color AL = 3 ± 1; urine color PER = 2 ± 1). Fluid volume consumption was significantly higher during the AL condition compared to PER (p = 0.05). Thirst significantly increased from pre to post run regardless of treatment (p<0.001), however, there were no differences between the groups (p = 0.492). Feelings of fullness did not change pre-post trial (p = 0.304) or between trials (p = 0.958). CONCLUSIONS: Increased fluid availability allows for increased fluid consumption without the negative experience of GI discomfort. Individuals should consider having regularly available fluid during exercise to increase the volume of fluid consumed and mitigate dehydration.

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