Marginal effects of a large caffeine dose on heat balance during exercise‐heat stress
Abstract
The use of caffeine supplements in athletic and military populations has increased in recent years. Excessive caffeine consumption in conjunction with exercise in a hot environment may predispose individuals to heat illness. 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% VO 2peak 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 (T b) 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 T b 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 T b 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.
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In a study using the same caffeine dose, mean body temperature was significantly higher by 0.27 degrees Celsius one hour after caffeine consumption than with placebo only at the beginning of exercise, whereas no differences between caffeine and placebo were observed with respect to core, skin or mean temperature during exercise.
“Conversely, in another study using the same caffeine dose, mean body temperature was significantly higher (by 0.27 C) one hour after caffeine consumption than with placebo only at the beginning of the exercise (cycling for 30 minutes at 50 % of VO 2peak in a 40 °C and 25 % relative humidity environment), whereas no differences between caffeine and placebo were observed with respect to core, skin”
From Scientific Opinion on the safety of caffeine (2015) · cites this paper as Ely et al., 2011
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- Authors
- Ely, B. R., Ely, M. R., & Cheuvront, S. N.
- Affiliations
- U.S. Army Research Institute of Environmental Medicine (US)
- Venue
- International Journal of Sport Nutrition and Exercise Metabolism
- Publisher
- Human Kinetics
- Published
- 2011-02
- Volume
- 21
- Issue
- 1
- Pages
- 65-70
- ISSN
- 1526-484X (ISSN-L)
- 1543-2742
- OpenAlex
- W2146917559
- Semantic Scholar
- 749ab70663f7df5e0d89480575a9a0546d7586f2
- Cited by
- 33
- References
- 34
- Citations by year
- 2025: 4 · 2024: 5 · 2022: 3 · 2021: 3 · 2020: 1 · 2019: 2 · 2018: 2 · 2017: 1 · 2016: 2 · 2015: 2 · 2014: 3 · 2013: 2 · 2012: 1
- FWCI
- 1.53
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- International Journal of Sport Nutrition and Exercise Metabolism (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Physiology › Thermoregulation and physiological responses
- Health Sciences › Medicine › Pharmacology › Coffee research and impacts
- Health Sciences › Medicine › Rehabilitation › Exercise and Physiological Responses
- Keywords
- caffeine, heat balance, heat stress, exercise in the heat, heat-related illness, body temperature, thermogenesis, thermal energy storage, thermal comfort, military personnel, endurance performance
- MeSH terms
- Adolescent, Adult, Body Temperature Regulation, Caffeine, Central Nervous System Agents, Double-Blind Method, Hot Temperature, Humans, Male, Oxygen Consumption, Stress, Physiological, Exercise, Young Adult
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