2023-07-11 13:47:02
Numerous studies have been carried out on the temperatures preferred by different animal species to keep their metabolic rates to a minimum and therefore their energy consumption low. However, curiously, much less information is available on the upper limits of the neutral thermal zone in humans.
Understanding at what temperatures human metabolism begins to increase and how it varies between people can have important implications in areas such as working conditions, sport, medicine and international travel.. New research is providing fundamental information about how we react in suboptimal environments and how “optimal” differs between people with different characteristics.
Between 40 °C and 50 °C
An ongoing study conducted at the roehampton university in the United Kingdom has revealed the existence of an upper critical temperature for humans, probably between 40°C and 50°C. The authors of this study presented their findings at the SEB 2023 Centenary Conferenceorganized by the Society for Experimental Biology (1). Additional research is currently underway to explain the increase in metabolic energy costs at high temperatures.
The teacher Lewis Halsey and his team have discovered that the resting metabolic rate, which is a measure of how much energy the human body consumes to keep running, may be higher when people are exposed to hot and humid conditions. In addition, they are investigating how temperatures above the critical temperature affect cardiac function and how these effects vary among people with different characteristics, such as age and physical condition.
Responses of Cardiac Function to Heat
“We find significant differences in cardiac function responses to heat between different groups of people, and most interestingly, we also found striking differences between men and women in terms of their cardiovascular responses to heat.”, emphasizes Professor Halsey. The team used a state-of-the-art echocardiograph to carefully measure heart function during the study.
Despite the difficulties associated with using the equipment in hot conditions, experiments continue. The goal is to get a more complete picture of how the body responds to heat stress, its ability to adapt, the limits of these adaptations and, most importantly, how the responses vary from one individual to another. In a world that is constantly warming, this knowledge becomes increasingly important.
References (1) Heating people lying down – what happens at the upper limit of the human thermoneutral zone? Society for Experimental Biology.
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