Thermoregulatory effects of caffeine ingestion during submaximal exercise in men.

Dunagan N, Greenleaf JE, Cisar CJ.
Aviat Space Environ Med 1998; 69:1178­81.

Abstract

Background: The exclusive effect of caffeine ingestion on exercise thermoregulation is unclear; data indicate that caffeine may have a positive effect, a negative effect, or no effect. Methods: Rectal (TRE) and mean skin (¯TSK) temperatures, skin heat conductance (HSK), and sweat rate (MSW) were measured during 30 min of rest and subsequent 70 min of submaximal cycle-ergometer exercise (67% VO₂PEAK) in 11 aerobically conditioned men (mean ± SD 29 ± 6 yr, 49 ± 6 mL · min^-1 · kg^-1VO₂PEAK) under two conditions: a caffeine (10 mg · kg^-1) ingestion (CI) session and a noncaffeine ingestion (NCI) control session. Results: There were no significant differences in physiological or thermoregulatory parameters during exercise: ¯X (±SE) end exercise levels for the NCI and CI sessions, respectively, were VO₂ = 2.50 ± 0.09 vs. 2.55 ± 0.09 L · min^-1; heart rate = 145 ± 7 vs. 145 ± 5 bpm; HSK = 30 ± 3 vs. 28 ± 3 kcal · m^-2 · h^-1 · °C^-1; ·MSW = 393 ± 35 vs. 378 ± 36 g · m^-2 · h^-1; and TRE = 38.3 ± 0.2 vs. 38.4 ± 0.1°C. Control ¯TSK was lower than that for CI by 0.4 to 0.5°C at rest and during exercise. Conclusion: Ingestion of a high level (10 mg · kg^-1) of caffeine has no effect on skin heat conductance, sweating, or the rate of increase and final level of rectal temperature during moderate, submaximal leg exercise.

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Table of Contents for Volume 69, Number 12 of the ASEM journal.