Keeping warm - how the body does it...

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SGL70

Full Member
Dec 1, 2014
613
124
Luleå, Sweden
I thought I should contribute a bit to the forum, with something cold again....I like winter....that is a good thing, since we have so much of it.

It is not the complete human knowledge on how the body works (in the cold), of course. I hope it makes waiting for the bus (and the like) a more pleasant experience :)


Here goes:

Man is a mammal that operates at its best when the surrounding temperature is 27C (in rest). At that temp we don’t sweat or freeze – the body is balanced temperature wise. Our skin temp is at that point approximately 33 – 34C.

The body aims at maintaining a constant core temperature at 37C for the internal organs to work at their best. During winter, adjustments have to be made in order to maintain that temp – Put on clothes, move, eat and drink. But that is not all that is going on. The body has weapons of its own to combat changes in temperature: Blood circulation, Sweating and Shivering. All aimed at protecting the body core: Brain, heart, lungs, liver, kidneys and the spinal cord.

Blood circulation:
The body is quite good at regulate the temperature by letting the blood flow from the core to the surface, or vice versa.
If the core temp is too high, the body sends the blood to the surface to be cooled and thus letting of excess heat. It easily observed as the skin reddens when you are hot.

On the other hand, if the core is too cold, the opposite happens and the surface turns pale. As a consequence, the legs and arms are getting less blood which leads to impaired motor skills. If the temperature in the hands sinks below 15C, they get practically useless – you cannot zip up your jacket or text your buddy.

A lot of heat is lost via the head, as that core part is continuously kept warm. As the brain constantly needs oxygen, it cannot be controlled by shutting down blood flow to preserve heat.
Some interesting numbers: Of the heat loss you experience at -10C, half is lost via the head, if you don’t have a hat on. At -20C, that number is 75%.
In effect: Cold feet? Put a hat on!

Sweating
If the body temperature increases as a result of hard labour or because you have too much clothes on, the blood are redirected to the surface for being cooled. Sometimes, this is not enough to keep the body in balance. At this point you start to sweat and the body tries to make the sweat evaporate from the skin. This requires heat (=draws it from the body) and it lowers the core temperature.
0.5 – 1 liter of sweat is evaporating from the skin per 24 hours when in rest. Even when it is cold.
During hard labour, you could lose 4 liters per hour.

When you are at risk of sweating, you need to adjust the clothing as well as make sure to ventilate out excess heat. This can be done by removing hat and gloves, unbuttoning the short or opening the fly.

The main reason for wanting to sweat as little as possible, is that water molecules are vastly better than air in transferring heat (I have the number 20 times as good, in my head. I do not know where that comes from, though). That kind of heat transfer can in turn cause a rather big drop in core temperature.

Shivering
Shivering is involuntary muscle contractions aimed at raising core temperature. It starts slow and culminates in massive shaking of the whole body.

Shivering is the body’s own protection against (excessive) cooling and it is a really important signal to do something (get indoors, add clothes, eat or drink something warm)


That is all, methinks.


Cheers,
Greger
 

SGL70

Full Member
Dec 1, 2014
613
124
Luleå, Sweden
Thanks folks,

...I have never frozen more than in damp and soggy winter condition...those are the worst imo. Cold and dry is rather easy to deal with...damp...that is another animal.

Cheers
Greger
 

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