How hot is too hot for the human body to function?

New evidence suggests the human body may stop functioning when the temperatures outside climb from 40 to 50 degrees Celsius. The normal human body temperature is 37 degrees Celsius.

The latest research was presented at the annual Society for Experimental Biology conference in Edinburgh, Scotland, on July 6. While the first set of experiments related to the human body's temperature was published in the journal National Library of Medicine in 2021, the second set of experiments mainly focused on heat and heart activity.

The scientists at the University of Roehampton, England said that if the temperatures rise higher, then people may start breathing heavily and their heart rates may go up.

"People are typically quite good at acclimating to heat, up to a point," said Lewis Halsey, a professor of life and health sciences at the University of Roehampton in England who conducted the research, according to NBC News.

While the first set of experiments measured people's resting metabolic rates, core temperatures, blood pressure, heart rates and breathing rates, the second one tries to find the upper limit that overwhelms the human body's refences against heat.

The study showed that at 40 degrees Celsius and 25 per cent humidity, participants' metabolic rates increased by an average of 35 per cent compared to the baseline, but their core body temperatures did not go up.

However, at 50 degrees Celsius and 50 per cent humidity, people's core temperatures rose by an average of 1 degree Celsius. People's metabolic rates also rose by 56 per cent, and their heart rates went up by 64 per cent.

Previous studies have shown that the maximum temperature that the human body can handle is 42.3 degrees Celsius. And when it goes above this, it could denature proteins and cause irreparable damage to the brain.