Fact of the day

Saturday, 5 September 2026

Environmentwell supported · human dataDiscovery of the day

Pooled results from 11 randomised trials in athletes (215 participants, mean age 26.09 years, 91% men) found heat acclimation improved time-trial performance and lowered maximal heart rate by 7 beats per minute, but produced no significant change in VO2max, exercise heart rate, core temperature, mean skin temperature, plasma volume or blood lactate. Changes in thermal comfort and perceived exertion were judged too small to be meaningful.

Study design
Meta-analysis
Journal
J Sports Sci Med
Evidence
well supported

What it shows: Reasonable evidence but thin on the ground: results pooled from 11 trials with 215 athletes between them, and 91% of those athletes were men, so it says little about women. The performance gain was modest and most of the physiological markers people expect heat training to shift did not budge.Meta-analysis · J Sports Sci Med

Physiological Responses to Heat Acclimation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Sports Sci Med 2019Read the study →

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