Thermoregulatory responses to exercise in the heat: chronic caffeine intake has no effect

M. Roti; D. J. Casa; A. Pumerantz; G. Watson; D. A. Judelson; J. Dias; K. Ruffin; L. E. Armstrong

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Thermoregulatory responses to exercise in the heat: chronic caffeine intake has no effect

Journal article

Peer reviewed

Thermoregulatory responses to exercise in the heat: chronic caffeine intake has no effect

M. Roti, D. J. Casa, A. Pumerantz, G. Watson, D. A. Judelson, J. Dias, K. Ruffin and L. E. Armstrong

Aviation, space, and environmental medicine, Vol.77(2), pp.124-129

2006

PMID: 16491580

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Abstract

Space life sciences

INTRODUCTION: Authorities advise individuals to refrain from caffeine intake before or during exercise, especially when performed in the heat, due to potential fluid-electrolyte imbalances that exaggerate physiological strain. Yet, military personnel are often deployed to hot environments and must perform under sleep-deprived conditions where caffeine would be an ideal intervention strategy to enhance physical and cognitive performance. PURPOSE: To assess the effects of controlled chronic and acute caffeine ingestion on fluid-electrolyte, physiological and thermoregulatory responses during an exercise heat tolerance test (EHT). METHODS: Subjects were 59 active, college-aged males (mean +/- SE 21.6 +/- 0.4 yr, 177.9 +/- 0.8 cm, 75.4 +/- 1.0 kg, 11.1 +/- 0.7% body fat) who were randomized and stratified by age, bodyweight, and body composition into three groups. All subjects equilibrated caffeine intake at 3 mg x kg(-1) x d(-1) for days 1-6. On days 7-12, they consumed a treatment dose of either 0 (G0), 3 (G3), or 6 (G6) mg x kg(-1) x d(-1). Fluid-electrolyte and physiological measures were made on day 12, 1 h after caffeine intake, during the EHT (90 min walking, 1.56 m x s(-1), 5% grade; dry bulb temperature, 37.7 +/- 0.1 degree C; relative humidity, 56.3 -1.5%). RESULTS: There were no between-group differences (p > 0.05) in plasma, urinary, thermoregulatory, cardiovascular, and perceptual variables across time (pre- vs. post-EHT), although some of these variables increased significantly over time (p < 0.05). EHT time was significantly greater in G3 (86 +/- 2.0 min) vs. GO (75 +/- 3.3 min, p < 0.05). DISCUSSION: Acute caffeine ingestion, in chronically consuming subjects (3 and 6 mg x kg(-1) x d(-1)) did not alter fluid-electrolyte, exercise endurance or thermoregulatory responses during EHT when compared with G0.

Details

Title: Thermoregulatory responses to exercise in the heat: chronic caffeine intake has no effect
Authors/Creators: M. Roti
D. J. Casa
A. Pumerantz
G. Watson
D. A. Judelson
J. Dias
K. Ruffin
L. E. Armstrong
Publication Details: Aviation, space, and environmental medicine, Vol.77(2), pp.124-129
Publisher: Aerospace Medical Association
Identifiers: 991005548868407891
Copyright: © 2006 Aerospace Medical Association
Murdoch Affiliation: College of Health and Education
Language: English
Resource Type: Journal article

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Collaboration types: Domestic collaboration
Citation topics: 1 Clinical & Life Sciences; 1.287 Dietary Stimulants; 1.287.1516 Coffee and Caffeine
Web Of Science research areas: Public, Environmental & Occupational Health; Sport Sciences
ESI research areas: Clinical Medicine