Caffeine ingestion compromises thermoregulation and does not improve cycling time to exhaustion in the heat amongst males.
Caffeine supplementation
Endurance performance
Ergogenic
Heat
Thermoregulation
Journal
European journal of applied physiology
ISSN: 1439-6327
Titre abrégé: Eur J Appl Physiol
Pays: Germany
ID NLM: 100954790
Informations de publication
Date de publication:
03 Apr 2024
03 Apr 2024
Historique:
received:
24
07
2023
accepted:
04
03
2024
medline:
3
4
2024
pubmed:
3
4
2024
entrez:
3
4
2024
Statut:
aheadofprint
Résumé
Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. In a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). There was no effect of caffeine supplementation on cycling time to exhaustion (TTE) (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate (WBSR) by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P < 0.001) compared to placebo. Core temperature was higher by 0.6% (P = 0.013) but thermal comfort decreased by - 18.3% (P = 0.040), in the caffeine condition, with no changes in rate of perceived exertion (P > 0.05). The greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.
Identifiants
pubmed: 38568259
doi: 10.1007/s00421-024-05460-z
pii: 10.1007/s00421-024-05460-z
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Informations de copyright
© 2024. The Author(s).
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