Jones, E. J., Bishop, P. A., Green, J. M., & Richardson, M. T. (2007). Effects of metered vs. bolus water consumption on urine production and rehydration. ACSM Annual Meeting New Orleans, Presentation Number 730.

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This study compared the effects of a rapid bolus and a slower metered water consumption rate on urine production and post-exercise rehydration. Males (N = 8) dehydrated to -2% body weight through moderate exercise in a hot environmentally controlled chamber (35C). Breakfast and lunch were standardized during the eight-hour data collection periods with nutritional intake repeated within Ss one day before the trials. Rehydration was performed using a volume of water equal (100%) of that lost during exercise either as bolus consumption (100% of volume consumed in one hour) or metered consumption (12.5% of volume every 30 minutes for four hours). Collected urine volume was used to assess hydration efficiency (water retained vs. water lost) and net fluid balance at eight hours.

Mean urine outputs were 420 ml for the metered condition and 700 ml for the bolus condition. Hydration efficiency was greater for the metered than the bolus condition.

Implication. Metered fluid replacement in dehydrated individuals results in a better fluid balance than if the replacement were attempted in a large amount over a short period.

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