It's true, rigorous exercise can keep our bodies warm for hours after we stop. Why? That's what Gina Kolata tries to reveal in a recent Personal Best column. Trouble is, no one really knows why. One theory, put forth by Glenn Kenny, a professor in the School of Human Kinetics at the University of Ottawa, claims simply that the body has a hard time getting rid of all the heat generated by exercise. Kenny says his research disproves the widespread (and optimistic) conviction that our metabolism remains elevated after exercise and we therefor continue to burn calories. Another researcher, one who worked with hardcore athletes–sprinters– found that their metabolism did remain elevated for as long as seven hours after exercise, and suggests that the robust metabolism could be keeping his athletes warm. Maybe. Finally, Kolata offers this explanation to why we remain warm hours after exercise: "It might be caused by…the body’s efforts to repair subtle tissue damage from all that exercise. The immune system can kick in, and so can enzymes that repair muscles and require heat-producing energy."
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Saturday, April 19, 2025
confirm this theory with a mechanical engineer, our body is mostly water. water absorbs heat like a large sponge and as the body works out the heat is stored. i’m sure it would take hours to convect that heat off, plus the metabolism slowly resets adding to the heat
Depends on how much the average body temperature can be increased.
The sensible heat capacity of 150 lbs of water is 150 BTUs/degree F or about 38 food calories/F.
With 0.4m^2 exposed skin, say the face, arms and legs, and an air-skin heat transfer coefficient of 15 watts/m^2-C, it will take at least 150 watts [138 cal/hr] to keep the skin temp a comfortable 80 F when the air temp. is 40F.
That’s at least twice the calories it takes to sit in a chair.
To store enough sensible heat the average body temp. would have to be raised 4 degrees for each hour the body remains warm after the exercise.
The temperature of most of the body is precisely regulated so the hands and feet will have to _really_ increase in temperature to make up the difference.
The only explanation as to why a body will stay warm hours after exercise is due to an increase in metabolism.
Bret Cahill
Most of the body temperature is precisely regulated and there just isn’t a whole lot of sensible heat capacity available in warm hands and feet.
It must be some increase in metabolism. That should be easy to measure from a CO2 or O2 balance.
Now maybe if the athletes ingested a lot of parafin that melted at 99 F they could exploit the latent heat as it resolidified to stay warm . . .
Bret Cahill
It seems to make some sense that the heat is generated from the muscle’s. And the area’s of the body that are used to shed the heat are area’s that have little to no muscle, like the head, feet, and hands. There must be a lot of friction going on in the muscle as it is being used, as well as when rebuilding itself from that use. So muscle creates the heat, and the water stores that heat.