Mon. Jul 22nd, 2024

Heat exposure over an extended period of time can be fatal

The higher limit of the human body’s thermoneutral zone was the subject of an experiment.

According to recent research from the University of Roehampton in England, when outside temperatures exceed 40 degrees Celsius (104 degrees Fahrenheit), the human body may stop operating properly and lose the ability to expel excessive heat. The latest study was recently presented at the Society for Experimental Biology‘s annual meeting in Edinburgh, Scotland.

Global heat waves right now are getting close to, if not over, these thresholds.

Because almost all of the body’s produced sweat evaporates, cooling the body, in hot, dry conditions, wet-bulb temperatures are not a good indicator of what the essential environmental limitations are. However, the amount of perspiration that humans can produce is limited, and the hotter the air, the more heat we produce.

Effects on human body:

The top limit of the thermoneutral zone was the subject of a second set of studies carried out by scientists at the University of Roehampton in England. Investigators discovered that the thermoneutral zone’s top boundary most likely lies between 104°F and 122F (40 to 50 degrees Celsius).

A temperature range known as the thermoneutral zone allows the body to maintain its optimal core temperature of 37°C or 98.6°F without having to raise its metabolic rate or use more energy.
According to studies, the zone’s lowest temperature is 28 °C (82.4 °F).

According to one study, the highest limit may be around 32°C (89.6F), which is the temperature at which people begin to perspire. However, according to a different study, the metabolic rate begins to rise at 40°C (104°F).

Conduct of the study:

The researchers enlisted 13 healthy participants between the ages of 23 and 58 for the study. There were seven female contestants.

Each subject spent an hour relaxing while being exposed to five different temperatures.The researchers measured a number of parameters during each condition and at baseline, such as body and skin temperatures, blood pressure, sweating rate, heart rate, breathing rate, volume of air inhaled and exhaled per minute, and movement levels.


At 40°C (104F) and 25% RAH, the participants’ metabolic rate increased by 35%, while at 40°C (104F) and 50% RAH, it climbed by 48%.

Although the metabolic rate was not greater in the 50°C and 25% RAH condition compared to the 40°C and 25% RAH condition, it was 56% higher than baseline in the 50°C (122F) and 50% RAH condition.

At the 40°C-25% RAH condition, the increase in metabolic rate was not followed by a rise in body temperature. Participants in the 50°C-50% RAH condition, however, noticed a 1°C (1.8 Farenheit) increase in core body temperature. These results, according to the researchers, imply that the body can expel heat at 40 °C (104 °F), but not at 50 °C (122 °F).

The subjects in the 50°C-50% RAH group sweated 74% more and had a 64% higher heart rate than baseline, according to the study.They added that participants in the 50°C-50% RAH group experienced higher myocardial workload compared to baseline, suggesting their hearts needed more oxygen to sustain peak performance. In addition, their capacity to breathe grew by 78% per minute and their breathing rate increased by 23%.

The scientists found that drinking water did not make the body cool under any of the circumstances.

By Parvathy Sukumaran

Parvathy Sukumaran is a Content Creator and Editor at JustCare Health. She is an Educator and a Language Lecturer. She holds a Bachelor's Degree in Education and an M.A in English Literature. She is passionate about writing, archaeology, music and cooking.

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