- Researchers investigated when the body starts exerting more energy to keep itself cool at high temperatures.
- They found that this upper-temperature limit lies between 104F (40℃) and 122F (50℃) when the human body stops functioning optimally.
- Further studies are needed to understand how this happens and offer insights as heatwaves and unusually warm temperatures continue to impact regions across the globe.
The human body may lose the ability to rid of excessive heat and stop functioning optimally when outside temperatures reach beyond 104 Fahrenheit (40 degrees Celsius), according to new research.
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 98.6 Fahrenheit or 37℃elsius.
Studies show that the zone’s lower limit is 82.4F or 28℃. 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 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 89.6F (32℃) as this is when humans start to sweat. Another study, however, noted that the metabolic rate starts to increase at 104F (40℃).
A follow up study of a 2021 investigation found that the thermoneutral zone’s upper limit likely lies between 104F (40℃) and 122F (50℃).
The researchers noted that drinking water in each of the conditions did not cool the body.
The findings appear to shed more precise light upon the body’s responses to sustained heat and humidity, and upon both the nature and mechanisms of enhanced metabolic rate that also arise in response to such conditions.
Further research into the upper limit of the thermoneutral zone could inform and affect change for important policies on working conditions, sports, medication, and international travel.
Sources: https://www.medicalnewstoday.com/articles/how-hot-is-too-hot-for-the-human-body-heart-metabolic-rate; National Institutes of Health, https://www.nih.gov
