Pagnotta, K. D., Casa, D. J., Gavin, K. E., & McDowell, L. M. (2012). Caffeine’s effect on hydration and body temperature during exercise in ?26.6°c environments: A systematic review. Presentation 1584 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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This study analyzed published literature to determine how caffeine effects hydration and core temperature while exercising in a warm or hot environment. Two independent searches were completed in various databases for keywords caffeine, core temperature, and exercise, as well as caffeine hydration status and exercise, using a variety of search terms. Inclusion criteria included original research with human Ss, controlled; counter-balanced hydration strategies; valid measurements of hydration status and core temperature; caffeine dosages of 3-9 mg/kg body mass administered less than three hours prior to exercise; exercise lasting greater than 30 minutes; and environmental conditions greater than or equal to 26.6°C. Quality control was obtained by a PEDro score of greater than or equal to 7 and two independent reviews of each article. Studies were excluded if they included time to exhaustion as the exercise component, the effects of caffeine could not be isolated, or they had no control group. The initial search revealed 342 studies and 49 were further analyzed. 41 studies were excluded for not meeting the inclusionary criteria, leaving eight studies for inclusion. Studies with multiple trials examining various doses of caffeine were counted as separate studies, resulting in a total of 12 possible data sources.

Independent of the mode used to assess, caffeine had no effect on hydration status.

Implication. Caffeine has little to no physiological effect on heat tolerance and hydration status.

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