Rehydration Following Exercise-Induced Dehydration
Condition: Dehydration Related to Exercise
MeSH terms: Dehydration
Study type: Interventional

Summary: 
      Athletes participating in multiple training sessions a day can be at increased risk of
      suboptimal hydration and heat illness during their second training session, especially when
      the environment is hot and humid. With the exception of the absolute volume of water
      delivered by a rehydration beverage, characteristics of the beverage consumed play a role in
      the recovery and completeness of rehydration. The amount of sodium in the beverage has been
      shown to be a primary factor in rehydration. Recently, an effect of the carbohydrate
      concentration of the beverage was been reported, with its effects mediated by the renal
      system in response to elevated serum insulin. The purpose of this study is to compare sodium
      and carbohydrate effects on rehydration and recovery.
    

Detailed description: 
      The effectiveness of beverage composition will be evaluated by modifying the sodium content
      and carbohydrate content of the beverage. Hypothesis: Completeness of rehydration will be
      greater in the beverage with higher sodium concentration. It is also hypothesized that
      electrolyte-carbohydrate beverages will promote rehydration that exceeds that of consuming
      placebo (water). Using a randomized balanced-treatment crossover design, physically trained
      males (18-35 yrs) will participate in intermittent exercise for 85 to 100 minutes in three
      experimental trials of variable intensity training in the heat (30 +/-3 C) followed by a
      rehydration-recovery period. Exercise will be done at varying intensities (intermittent
      intervals) ranging from 50% to nearly 100% of maximum oxygen uptake (max VO2) determined
      prior to the experimental trials. During the 85 to 100 min of exercise, no fluids will be
      given during the trial to elicit an acute reduction in body mass of approximately 2.5 to 3%
      (standardized for each subject). Following exercise, 100% of the volume of fluid lost will be
      replaced with one of the beverages. Beverages will be ingested in six aliquots over a 1-hr
      period given at the end of the trial. Retention of fluid will be calculated by measuring
      volume of urine lost at 30, 60, 135, and 210 min following ingestion of the rehydration
      beverage. The primary outcome variable is the percentage of fluid retained, i.e., the
      difference between volume ingested and cumulative urine produced in 3.5 h as a percentage of
      volume ingested. Body mass, urine specific gravity, total body water, and ratings of vigor
      and affect will be assessed prior to exercise, after exercise in a state of dehydration, and
      at 210 min post-exercise following rehydration. A one-way ANOVA will be used to test the
      hypothesis for rehydration, the primary outcome variable.
    

Intervention name(s): Water with flavoring and non-nutritive sweetener.; High-Na low-CHO beverage; Low-Na high-CHO beverage
Intervention type(s): Other; Other; Other
Intervention description(s): A volume of fluid (water) was given after exercise to return each subject's body mass (to euhydration).; A volume of fluid (high-Na, low-CHO) was given after exercise to return each subject's body mass (to euhydration).; A volume of fluid (low-Na, high-CHO) was given after exercise to return each subject's body mass (to euhydration).
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: dehydration; exercise; rehydration; sodium; water; carbohydrate