Caffeine, Fluid-Electrolyte Balance, Temperature Regulation, and Exercise-Heat Tolerance

Lawrence E. Armstrong; Douglas J. Casa; Carl M. Maresh; Matthew S. Ganio

Disclosures

Exerc Sport Sci Rev. 2007;35(3):135-140. 

In This Article

Temperature Regulation and Exercise-heat Tolerance

Although few studies have evaluated the influence of environmental temperature on caffeine effects or on exercise-heat tolerance, Table 3 presents such data from studies conducted in mild-to-hot environments. Regarding temperature regulation, rectal and skin temperatures (columns 3 and 4) represent heat storage in central and peripheral tissues. Metabolic rate and sweat rate (column 5) relate to heat production and heat loss, respectively. Heart rate reflects circulatory strain during heat exposure, and exercise duration is a classic index of heat tolerance.

The six studies in Table 3 present a unified message: caffeine intake (vs control) exerts little or no influence on human thermal balance, circulatory strain, and exercise time to exhaustion. Thus, restricting dietary intake of caffeine is not scientifically and physiologically supported. This conclusion includes running, cycling, and prolonged walking in mild-to-hot environments. Despite these results, most of these studies provide low statistical power because of small sample size; some did not use subjects as their own controls. Additional studies should examine exercise in a hot environment.

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