Scientists have clarified how much heat a person can endure

A new study by scientists at the University of Ottawa shows: the limits of our ability to regulate body temperature in heat are lower than previously thought. This is an important finding in an era of global warming.

Read more: Robert D. Meade et al, Validating new limits for human thermoregulation, Proceedings of the National Academy of Sciences(2025). DOI: 10.1073/pnas.2421281122

The study was conducted at the Human and Environmental Physiology Laboratory (HEPRU). Its results were published in the journal Proceedings of the National Academy of Sciences. The scientists found that in many parts of the world, heat and humidity are already approaching limits beyond which the human body can no longer cope with overheating.

We confirmed that previous models overestimated the body's ability to regulate temperature in extreme heat," says Professor Glen Kenny, one of the study's leaders.

To find out the real limits of thermoregulation, the team of scientists used a proven method - the so-called "heat steps". The experiment involved 12 volunteers who were exposed to high temperatures and humidity in stages. Each participant then returned to the lab to spend up to nine hours in conditions above their individual limit - at 42°C and 57 per cent humidity. This corresponds to a "perceived temperature" (humidex) of around 62°C.

The results were unequivocal: the participants' body temperatures rose inexorably and many were unable to complete the full experiment. This was the first scientific confirmation that the limits defined by the methods of past decades were indeed underestimated.

The study also emphasises how dangerous prolonged exposure to heat becomes.

Our findings confirm: the body experiences serious physiological stress even at temperatures previously considered acceptable," says one of the authors, Dr Robert Mead.

These data have already begun to be used in climate models. They are helping to better assess health risks and develop heat adaptation measures, from building "cooler" urban spaces to new recommendations for health services.