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#87709 - 03/08/07 12:47 AM Re: Survival Myths [Re: Russ]
Lasd02 Offline
Member

Registered: 12/14/05
Posts: 130
Loc: Pasadena, Calif.

RAS,

One of the articles I linked to above seemed to show that test subjects immersed suddenly in cold water who did not have their heads covered, did in fact show a higher percentage of core temperature drop than those whose heads were covered.

The total heat loss over the bodies surface area didn't change, but the bodies reaction to the sudden cold probably caused the vasoconstriction that changed the core heat loss percentage (I could be misunderstanding the article, I'm not a scientist).

I'm not sure how this could be utilized in a survival situation unless you're willing to lug a Mustang suit around with you!

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#87710 - 03/08/07 12:52 AM Re: Survival Myths [Re: Lasd02]
leeana Offline


Registered: 03/31/06
Posts: 21
Loc: so cal

page 2019 (8 of 18) of

http://www.ms-se.com/pt/pt-core/template-journal/msse/media/1106.pdf

quotes an interesting statement from a study in 1957.

"This means that at –4°C the heat loss from the head may amount to half the total resting heat production of the man."

http://jap.physiology.org/cgi/content/abstract/10/2/235

50% of RESTING heat production.

i think i'll keep my beanie on, thank you very much.

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#87713 - 03/08/07 01:44 AM Re: Survival Myths [Re: leeana]
Lasd02 Offline
Member

Registered: 12/14/05
Posts: 130
Loc: Pasadena, Calif.

Please, by all means keep your beanies on and I will do the same, but let's not do so out of ignorance. I believe the 1957 study you link to is the same one referred to here:

"Dr. Daniel I. Sessler, an anesthesiologist and expert on hypothermia at the University of Louisville medical school, said the popular myth stems from military experiments conducted five decades ago."

The popular myth being the 50% figure. I'm certain at the time, they were using the best techniques and instruments available such as they were. If you want to base your survival decisions on outdated data from 1957 while ignoring the current 10% figure from todays experts, go right ahead...just don't invite me on your next 2 week backcountry campout (yeah, likes that's gonna happen wink



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#87727 - 03/08/07 04:59 AM Re: Caffiene and alcohol [Re: Lasd02]
OldBaldGuy Offline
Geezer

Registered: 09/30/01
Posts: 5695
Loc: Former AFB in CA, recouping fr...
"...The rate of heat loss is relatively the same for any exposed part of the body, not simply the head..."

I just guessing here, but I suspect that most of us who buy into the hat thing do so on the assumption that, while outdoors in the cold, the ONLY part of the body that is exposed is the head, and possibly the hands. Most of us are wearing some form of clothing from the ground up, so if you are getting cold anywhere else, cover that exposed part with a hat, and you will feel warmer...
_________________________
OBG

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#87733 - 03/08/07 06:19 AM Re: Caffiene and alcohol [Re: OldBaldGuy]
Lasd02 Offline
Member

Registered: 12/14/05
Posts: 130
Loc: Pasadena, Calif.

Hey, I buy into the hat thing too, all I'm saying is that it's good to know that when I cover my head, I'm helping to keep in 10% of my bodies heat, not the 70% (or 50%, or 35%, etc.), I had always heard and believed. None of these experts are telling us it's no longer advisable to wear a hat, but isn't it better to know the truth?

If Garmin announced tomorrow that they were terribly sorry but they and all the other GPS manufacturers had been lying for several years, their units are only accurate to 1/4 mile at best, would we stop carrying them? I hope not, if I'm lost I'd rather know where I am to the nearest 1/4 mile than nothing at all, but It sure would be good to know. If ACR's PLB's typical operating life was reduced from 40 hours to 4 hours, would that prevent you from activating it when needed? Of course not, but again it sure would be good to know. 'Nuff said (I hope!).




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#87736 - 03/08/07 07:05 AM Re: Caffiene and alcohol [Re: Lasd02]
Susan Offline
Geezer

Registered: 01/21/04
Posts: 5163
Loc: W. WA
Some of the information from the Wilderness Medicine site seems rather poorly expressed, IMHO.

Did anyone notice the authors of these articles?

"These myths are explained and debunked by Dr. Murray Hamlet, DMV, Dr. Gordon Giesbrecht, PHD, and Frank Hubbell, DO."

Dr. Murray Hamlet, DMV (apparently, more properly, DVM), is a veterinarian who received his degree from Washington State University.

Dr. Gordon Giesbrecht, Ph.D is a professor at the University of Manitoba in Winnipeg, Manitoba, Canada, where he operates the Laboratory for Exercise and Environmental Medicine.

Frank Hubbell, DO is a Doctor of Osteopathic Medicine, and is the founder of SOLO (Stonehearth Open Learning Opportunities in Conway, NH).

A vet, a teacher and a doctor... why is the vet listed first?

Sue

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#87738 - 03/08/07 07:57 AM Wear a Hat When Your Feet are Cold [Re: Lasd02]
JCWohlschlag Offline
Some guy who wandered in…
Old Hand

Registered: 11/26/06
Posts: 724
Loc: Dallas, Pennsylvania, United S...
As for the “myth” about putting on a hat when your feet are cold, I sincerely doubt that it’s so cut-and-dry.

For one, if you’re cold, a large majority of your warm blood will be constricted into your core and head. So, where exactly are you losing most of your heat then? It may be true that you lose heat evenly when your body temperature is normal, but once your body temperature starts dropping, you’ll lose more heat from where the blood concentrates. If your feet are cold, it’s probably because the blood went somewhere else.

Secondly, I’ve seen only a little bit of discussion about hair. If you’re considering surface area to be the most significant factor, your hair increases your head’s surface area dramatically. In calm weather, your hair may be able to create a nice insulating layer. In more harsh weather, where this “myth” actually comes to practical use, the wind will be blowing your hair around so much that it may actually start acting as a heatsink.

Somehow I find more credibility in the various thermal images I’ve seen showing people in cold weather. These images normally show people in winter clothes as a dark colored body with a big, bright spot depicting their head. So, where are they losing the most body heat from then? This “myth” needs to be looked at in the big picture, as applied to people who are in a survival situation and are cold. If the norm for this scenario were to be naked, then maybe the difference in heat loss between your head and the rest of your body wouldn’t be significant. However, being naked is not the norm, and if you’re naked in the cold, you have bigger problems that to grab a hat. The myth simply means, in all its glory, “Don’t forget your hat.”
_________________________
“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin

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#87743 - 03/08/07 01:35 PM Re: Caffiene and alcohol [Re: OldBaldGuy]
frenchy Offline
Veteran

Registered: 12/18/02
Posts: 1320
Loc: France
I am - painfully - trying to understand this thread ...
and starting to wonder ...

"Did I miss something or what ?... Am I supposed to hike buck (sp?) naked (like that guy, doing exactly that in Great Britain... when he is not serving time in jail for exhibition !!! ), with only a hat on my head ?????"
(see my avatar ?!!)

I guess, then I would loose much more heat from other body parts .. blush blush

My own take (not a scientific one, I fear ..) on that "heat loss from head" stuff was (up to now...) that if you are normally dressed and wear NO HAT, then a great deal of heat is lost from the head area.
Covering your head might help keeping warm, more than adding a layer elsewhere.
OTOH, in the dead of winter, adding a parka over a simple T-shirt might beat the hat thing as far as rate of heat loss is concerned.... grin grin

___________________________

Edited :

Oooopsss... I had not read all the recent posts.
Looks like Raydarkhorse, or JCWohlschlag also said about the same thing, if differently ...


Edited by frenchy (03/08/07 01:40 PM)
_________________________
Alain

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#87758 - 03/08/07 03:43 PM Re: Caffiene and alcohol [Re: frenchy]
OldBaldGuy Offline
Geezer

Registered: 09/30/01
Posts: 5695
Loc: Former AFB in CA, recouping fr...
Yup, I think that as far as this topic goes, we have again reached the beating a dead horse stage...
_________________________
OBG

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#87761 - 03/08/07 03:56 PM Re: Caffiene and alcohol [Re: Susan]
Misanthrope Offline
Member

Registered: 09/08/05
Posts: 156
Loc: Chicago burbs
Thanks, Susan. I should have jumped on that myself. Always consider the source.

M
_________________________
I hear voices....And they don't like you.

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