Extreme Heat: Human Metabolic Rates Soar at 104-122°F

Researchers have identified an upper critical temperature (UCT) for humans, likely between 104-122°F, which causes a rise in resting metabolic rate in hot and humid conditions. The study reveals significant differences in cardiovascular responses to heat between sexes, as well as variations across age and physical fitness levels. Understanding these temperature thresholds and individual variations can have implications for working conditions, sports, medicine, and international travel. Ongoing research is also investigating how heart function is affected by temperatures above the UCT.