Steve Brown" <steve_at_brown-web.net> wrote: >> No one seems to know the answer to the first question, about the disappearance of the "ice cream headache" after a few days of exposure to cold water (surprising). The follow up question is this: Does the same type of adaptation, when applied to your whole body, have the potential to delay the onset of hypothermia? >> Steve, I do not have any authoritative, scientific studies at my fingertips to support such adaptation. Two pieces of "evidence" which suggest there may be long-term adaptation: 1. Sometime in the 19th century there was a missionary who got stranded on the coast of Argentina (Patagonia, actually) where the natives habitually hunted and lived in 40-50F air temps, sans clothing or furs. One might surmise the native population had self-selected (evolved) so they could handle this. The missionary survived, and was picked up about a year later, buck naked, and showing no ill effects. 2 There was a careful study done on cold water adaptation several years ago of extremities (fingers and hands, only), in the context of fish filleters who worked the slime line: experienced (read: habituated) filleters could stay on an 8-hour shift of work in 35F water with no loss of function. New employees could only tolerate 20 minutes, and then had to break for half an hour. Gradually, over a period of a month or so, new filleters could increase their tolerance for cold water exposure (hands only) and reach the same plateau as the old hands (pun intended). The tolerance could be maintained indefinitely if workers kept working in cold water. If they quit that, they lost the tolerance about twice as fast as they gained it: in other words, in about two weeks. The weakness in the second piece of "evidence" is that it only involves a small part of the body -- the investigators surmised adaptation mainly circumvented the usual shutdown of blood flow cold hands experience. This would mean those adapted would experience a __greater__ loss of body heat -- and would not increase their overall resistance to hypothermia. However, the study suggests there are adaptive mechanisms that change circulation patterns. If the body can effect a shutdown of peripheral, surfacial circulation, it would decrease the overall heat loss, and tht would delay hypothermia. (Note this is good physics: the outermost layer becomes a better insulator.) And, my personal experience: when I was regularly climbing and X-C-touring back in the 60's and '70's, I found that __for an equivalent set of conditions__ I needed much less insulation at the end of a several-day expedition than at the end. These were short trips of a week or so in subfreezing conditions. I expect that if I had been out expeditioning for 2 months, the cold adaptation would reach a max. In short, I think there is strong anecdotal evidence for adaptation, but I can not cite any quantitative scientific studies to confirm that. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Tue Mar 18 2003 - 22:14:19 PST
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