Re: [Paddlewise] Cold and skills

PeterO wrote:

> That body mass index is surely worth a lot. Differences in body surface area
> to mass ratio don't seem large enough to account for solidly built people
> lasting a day or so in cold water and thinner folks only lasting an hour or
> two. 

Peter, be careful here to avoid lumping people having a mass (of whatever 
source) in with people having a high fat/muscle content.  Muscle is not a 
good insulator, but it does contribute to mass.

> And I wouldn't think body fat is that great an insulator even though
> its sealed with an effective waterproof coating (skin). Really good
> insulators generally rely on trapping pockets of air small enough to avoid
> convective heat transport. 

I believe you are thinking of "really good insulators" here as ones with 
high insulating value compared to their _mass._  In the sea, high mass is 
not a disadvantage, as long as some positive buoyancy is maintained.  I 
suspect an inch of fat is as good an insulator as an inch of goose down, or 
nearly so.  It is our go-light, go-fast mentality which prejudices us 
towards lightweight insulators.  And, for structures, lightweight 
insulators are cheaper (air costs nothing) and work well between structural 
elements (aka walls).  Sea creatures don't need the same structural 
elements bipedal land mammals do ... we have quite a bit of "wasted" bone 
structure for paddling (e.g., legs are pretty useless to paddlers).

> So while thermal insulation is important, strikes me energy stored in fat or
> food could be particularly useful as well and might account for the striking
> difference in cold tolerance. Can fat be metabolised for fuel quickly enough
> to stay warm and might there be enough in larger people to last a day for a
> day or two?

In short, no.  Unlike bears and other similar mammals, we are not able to 
metabolize fat effectively without a carbohydrate input.  And, we do not 
store enough carbohydrate (as glycogen) in our bodies to use much stored 
fat as an energy source.

Peter, I think your skepticism about the insulating value of fat is 
misplaced.  Never mind there is not air trapped in it ... blubber is a very 
good insulator.  Just ask a whale.  Remember, they are mammals, also.

Fat people (what's this "solidly built" euphemism stuff, anyway?) are 
better survivors in cold water for their blubber.

-- 
Blubber Dave (channeling for the Steller sea lion he was three incarnations 
ago)
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