Slade Trillgon
T.R.I.A.D
75
   |
Posted - 2011.12.13 17:36:00 -
[1] - Quote
Adunh Slavy wrote: When air is warmer, it can hold a lot more moisture, that "sweat" has someplace to go, the moisture can escape your blankets/sheets and go into the warm air. When the air is cooler above your blankets, the water can not evaporate as easily, so it stays.
This is the same reason that there is dew and frost in the morning. During the night, the air temp drops, the water is forced out of the air and is deposited on the ground.
All that nice warm air under your blankets, in winter, holds all that water, sooner or later it gets saturated and it begins to "rain" under the blankets and leaves you all sweaty.
To give a name to the process described above.
Evaporative cooling, http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/sweat.html, is a very efficient way to cool the body. Bedding, sheets, and a shirt will keep the cool dry air from flowing over the body and wicking the moisture off the skin. This is why when working in the summer heat that you should not switch over to dry clothing during breaks as you have to then re-soak all that fabric before you start cooling the body at max efficiency. The rate at which you burn calories is effected highly by the ambient temperature.
As for the burning calories by shivering question, I found the following post, http://www.thenakedscientists.com/forum/index.php?topic=3326.0, which simplifies the concept pretty nicely.
Chris wrote: Shivering is a very efficient form of heat production which involves burning energy in muscles to release heat and so warm up the body.
As you know, muscles can only contract and so they're arranged in antagonistic pairs around joints; that is, one muscle moves the joint in one direction whilst its opposite number moves the joint back the other way.
During a movement one of the pair of muscles is activated whilst its antagonistic partner is switched off until just before the correct joint position is achieved.
But when you shiver both muscles are activated simultaneously so that they work against each other. As a result there is little of no net movement of the joint, but a huge amount of energy is burned. As muscles are only about 20% efficient i.e. 80% of the energy they burn turns into heat, this is a very good way to warm the body.
However, I agree with you that shivering is probably not as good at burning energy as sprinting.
Chris
EDIT: All that being said, if you are shivering to the point that it is buring off a high number of calories it is likely that you will not be sleeping very well, which I believe to a very good reason not to do this. Just do an extra half hour of vigorous activity each day and you will be close to the same energy expinditure
Slade |