Effect of caffeine ingestion on fluid balance during exercise in the heat and during recovery

  • Yang Zhang Department of Kinesiology, University of Alabama, Tuscaloosa, USA
  • S J Carter Department of Kinesiology, University of Alabama, Tuscaloosa, USA
  • R E Schumacker Department of Educational Studies in Psychology, Research Methodology, and Counseling, University of Alabama, Tuscaloosa, USA
  • Y H Neggers Department of Human Nutrition, University of Alabama, Tuscaloosa, USA
  • M D Curtner-Smith, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
  • M T Richardson Department of Kinesiology, University of Alabama, Tuscaloosa, USA
  • J M Green Department of Health, Physical Education, and Recreation, University of North Alabama, Florence, USA
  • P A Bishop Department of Kinesiology, University of Alabama, Tuscaloosa, USA
Keywords: Coffee, Diuresis, Hydration, Dehydration

Abstract

Background. The effect of ingestion of a common stimulant, caffeine, on fluid balance during exercise and recovery is not fully known. 

Objectives. To determine the effect of caffeine on fluid balance during exercise in the heat and during a 3-hour recovery period thereafter. 

Methods. In a randomised, controlled design, caffeine-naive participants (N=8) pedalled on a bike to achieve 2.5% baseline body mass loss in a hot environment in four separate conditions: with (C+) or without (C–) caffeine ingestion (6 mg/kg of body mass) prior to exercise, followed by (W+) or without (W–) 100% fluid replenishment (water) of the body mass loss during a 3-hour recovery period (yielding C+W+, C+W–, C–W+ and C–W–, respectively). 

Results. Mean (standard deviation) urine production was not different (p>0.05) regardless of rehydration status: 230 (162) mL (C+W–) v. 168 (77) mL (C–W–); and 713 (201) mL (C+W+) v. 634 (185) mL (C–W+). For the 3-hour recovery, caffeine ingestion caused higher hypohydration during rehydration conditions (p=0.02), but practically the mean difference in the loss of body mass was only 0.2 kg. 

Conclusion. In practical terms, there was no evidence that caffeine ingestion in moderation would impair fluid balance during prolonged exercise in the heat or during 3 hours of recovery.

Author Biographies

Yang Zhang, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
PhD
S J Carter, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
MSc
R E Schumacker, Department of Educational Studies in Psychology, Research Methodology, and Counseling, University of Alabama, Tuscaloosa, USA
PhD
Y H Neggers, Department of Human Nutrition, University of Alabama, Tuscaloosa, USA
PhD
M D Curtner-Smith,, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
EdD
M T Richardson, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
PhD
J M Green, Department of Health, Physical Education, and Recreation, University of North Alabama, Florence, USA
PhD
P A Bishop, Department of Kinesiology, University of Alabama, Tuscaloosa, USA
EdD
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Published
2014-06-15
Section
Articles