The human body may lose the ability to rid of excessive heat and stop functioning optimally when outside temperatures reach beyond 40 degrees Celsius (104 Fahrenheit), according to new research from the University of Roehampton in England.
The thermoneutral zone is a range of temperatures in which the body doesn’t have to increase its metabolic rate or exert more energy to maintain its ideal core temperature of 37℃elsius or 98.6 Fahrenheit.
Studies show that the zone’s lower limit is 28℃ or 82.4F. Below this, the body expends more energy to maintain its ideal temperature. One of the keys ways it does this is by shivering — when key muscle groups involuntarily contract to produce heat.
At higher temperatures, the human body uses other mechanisms to cool down, such as sweating and vasodilation of blood vessels at the skin surface to increase heat loss.
However, while the thermoneutral zone’s lower range has been established, its upper limit is still uncertain.
One study suggests that the upper limit may stand at around 32℃ (89.6F) as this is when human body starts to sweat. Another study, however, noted that the metabolic rate starts to increase at 40℃ (104F).
Further research into the upper limit of the thermoneutral zone could inform policies on working conditions, sports, medication, and international travel.
As a follow-up study of a 2021 investigation, researchers at the University of Roehampton in England conducted a second set of experiments to investigate the upper limit of the thermoneutral zone.
They found that the thermoneutral zone’s upper limit likely lies between 40℃ (104F) and 50℃ (122F).
