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Marginal effects of a large caffeine dose on heat balance during exercise-heat stress.
MedLine Citation:
PMID:  21411837     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
PURPOSE: To examine heat balance induced by a large dose of caffeine during exercise in a hot environment.
METHODS: Ten men, not heat acclimated and not habitual caffeine users, consumed either caffeine (CAF; 9 mg/kg) or placebo (PLA) before performing cycle-ergometer exercise for 30 min at 50% VO2peak in a 40 °C, 25% relative humidity environment while body temperature (core and skin) and ratings of thermal comfort (TC) were monitored. Heat-exchange variables were calculated using partitional calorimetry and thermometry.
RESULTS: Mean body temperature (Tb) was higher (p < .05) with CAF (37.18 ± 0.15 °C) than with PLA (36.93 ± 0.15 °C) at the start of exercise. Heat production was slightly higher (~8 W, p < .05) with CAF. There were no differences in heat storage, dry heat gains, TC, or Tb during exercise.
CONCLUSIONS: A caffeine dose of 9 mg/kg does not appreciably alter heat balance during work in a hot environment. The small increase in Tb observed with CAF was undetected by the participants and is unlikely to increase physiological strain sufficiently to affect endurance performance or risk of heat illness.
Authors:
Brett R Ely; Matthew R Ely; Samuel N Cheuvront
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  International journal of sport nutrition and exercise metabolism     Volume:  21     ISSN:  1526-484X     ISO Abbreviation:  Int J Sport Nutr Exerc Metab     Publication Date:  2011 Feb 
Date Detail:
Created Date:  2011-03-17     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100939812     Medline TA:  Int J Sport Nutr Exerc Metab     Country:  United States    
Other Details:
Languages:  eng     Pagination:  65-70     Citation Subset:  IM    
Affiliation:
Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Natick, MA.
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