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Consuming caffeine before exercise may increase physiological strain, including hyperventilation and decreased cerebral blood flow, under the heat. However, researchers at University of Tsukuba found that consuming caffeine during exercise may enhance performance in the latter stages of prolonged exercise in the heat without worsening physiological strain.

Tsukuba, Japan—Caffeine, which is present in various foods and beverages, is widely known to improve exercise performance. However, these ergogenic effects may not be observed under hot conditions. Previously, a research group found that caffeine consumption before exercise in the heat increases physiological strain, including excessive breathing associated with elevated core body temperature (hyperthermia-induced hyperventilation) and decreased cerebral blood flow. These physiological responses are attributed to a rapid increase in the blood caffeine concentration before exercise, which diminishes the ergogenic effects of caffeine.

In this study, researchers investigated the effects of intake of moderate doses of caffeine during exercise on performance during prolonged exercise in the heat in healthy young men and women. The results showed that blood caffeine levels gradually increased during exercise, and the duration of high-intensity exercise performed at the end of exercise was prolonged. In addition, the rating of perceived exertion was lower immediately before high-intensity exercise. By contrast, caffeine intake did not worsen hyperthermia-induced hyperventilation and cerebral hypoperfusion during exercise.

These findings indicate that consuming caffeine during exercise may be an effective strategy for improving exercise performance during prolonged exercise in the heat. Moreover, this approach does not worsen physiological strain at corresponding time points compared with a no-caffeine condition. However, caffeine intake resulted in greater cardiorespiratory and temperature strain at the end of exercise because of the improved exercise performance.

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This study was supported by Ministry of Education, Culture, Sports, Science and Technology in Japan (grant number: 22H00499).

Original Paper

Title of original paper:

In-exercise caffeine improves exercise performance in the heat without exacerbating hyperventilation and brain hypoperfusion

Journal:

Medicine & Science in Sports & Exercise

DOI:

10.1249/MSS.0000000000003792

Correspondence

Associate Professor FUJII Naoto
Researcher KATAGIRI Akira
Institute of Health and Sport Sciences, University of Tsukuba

Related Link

Institute of Health and Sport Sciences