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baloo_the_bear t1_izb0vj6 wrote

Metabolic activity continuously produces heat as a byproduct. Without a method of dissipating that heat, a person would quickly overheat and die.

Normal responses to hyperthermia include vasodilation and sweating as methods to facilitate heat transfer out of the body, but if the surrounding environment is already ‘too hot’ to allow dissipation the heat is trapped in the body and core temperature rises.

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perrochon t1_izb3wsy wrote

Just to add some napkin physics....

A human is producing ~100 watts of power at rest. Water's specific heat capacity is 4.186J/g. Humans consist of much water. Heating a 75kg bag of water 1 degree C using 100W takes 52 minutes.

https://www.google.com/search?q=4.184+joules%2Fg+*+75kg+%2F+100+watt

Normal body temperature is ~37C, life threatening is ~40C. ~41C starts irreversible protein denaturation. So give or take 4 hours to serious damage.

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NakoL1 t1_izb94r0 wrote

also of note if anyone's interested, is that 100W over 24 hours is 2.4 kWh or 8,640 kJ or 2,065 kcal

obviously the actual metabolic rate varies greatly, from around 60-70W or so during deep sleep to >1,000W during intense exercise. As well as between different people

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