Caffeine Exacerbates Hyperventilation and Reductions in Cerebral Blood Flow in Physically Fit Men Exercising in the Heat.
Blood Flow Velocity
/ drug effects
Blood Pressure
/ physiology
Body Temperature
/ drug effects
Caffeine
/ pharmacology
Cardiac Output
/ physiology
Central Nervous System Stimulants
/ pharmacology
Cerebrovascular Circulation
/ drug effects
Cross-Over Studies
Heart Rate
/ physiology
Hot Temperature
Humans
Hyperthermia
/ complications
Hyperventilation
/ drug therapy
Male
Middle Cerebral Artery
/ physiology
Physical Exertion
/ physiology
Physical Fitness
/ physiology
Placebos
Respiration
Single-Blind Method
Stroke Volume
/ physiology
Young Adult
Journal
Medicine and science in sports and exercise
ISSN: 1530-0315
Titre abrégé: Med Sci Sports Exerc
Pays: United States
ID NLM: 8005433
Informations de publication
Date de publication:
01 04 2021
01 04 2021
Historique:
pubmed:
13
10
2020
medline:
29
6
2021
entrez:
12
10
2020
Statut:
ppublish
Résumé
Caffeine is an exercise performance enhancer widely used by individuals engaged in training or competition under heat-stressed conditions. Caffeine ingestion during exercise in the heat is believed to be safe because it does not greatly affect body temperature responses, heart rate, or body fluid status. However, it remains unknown whether caffeine affects hyperthermia-induced hyperventilation or reductions in the cerebral blood flow index. We tested the hypothesis that under conditions inducing severe hyperthermia, caffeine exacerbates hyperthermia-induced hyperventilation and reduces the cerebral blood flow index during exercise. Using a randomized, single-blind, crossover design, 12 physically active healthy young men (23 ± 2 yr) consumed a moderate dose of caffeine (5 mg·kg-1) or placebo in the heat (37°C). Approximately 60 min after the ingestion, they cycled for ~45 min at a workload equal to ~55% of their predetermined peak oxygen uptake (moderate intensity) until their core temperature increased to 2.0°C above its preexercise baseline level. In both trials, ventilation increased and the cerebral blood flow index assessed by middle cerebral artery mean blood velocity decreased as core temperature rose during exercise (P < 0.05), indicating that hyperthermia-induced hyperventilation and lowering of the cerebral blood flow occurred. When core temperature was elevated by 1.5°C or more (P < 0.05), ventilation was higher and the cerebral blood flow was lower throughout the caffeine trial than the placebo trial (P < 0.05). A moderate dose of caffeine exacerbates hyperthermia-induced hyperventilation and reductions in the cerebral blood flow index during exercise in the heat with severe hyperthermia.
Identifiants
pubmed: 33044440
pii: 00005768-202104000-00020
doi: 10.1249/MSS.0000000000002537
doi:
Substances chimiques
Central Nervous System Stimulants
0
Placebos
0
Caffeine
3G6A5W338E
Types de publication
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
845-852Informations de copyright
Copyright © 2020 by the American College of Sports Medicine.
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