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Winter Harm: Cold Dangers

Cold can harm in subtle and quick ways, so it pays to be prepared.

I had only myself to blame. After a beautiful day of snowshoeing on Red Mountain Pass near Ouray, Colorado, I felt awful. By the time we returned to the car, the underside of my nose was sunburned, my skin was cold and clammy with sweat, and my shoulders were cramped from hunching them against the wind biting through my fleece. To add insult to injury, my husband kept making jokes about my chattering teeth.

Luckily this was just a day outing; if it had been an overnight excursion, my poor cold-weather management could have put me in serious trouble. The good news is that such winter consequences are easily avoided once you understand how cold affects your body.

Frigid, blustery, wet winter weather robs your body of precious heat four sneaky ways: through radiation, conduction, convection, and evaporation.

Radiation

In a house, radiators get hot and warm the air around them. Insulated walls hold in the heat and prevent the warm air from drifting off into the cold night. In the backcountry, appropriate clothing (see “Conduction” below for examples) and a good sleeping bag hold in the heat produced by your body. Just remember, if you wear the wrong kind of clothing or expose your skin, you’ll lose more heat through radiation as the temperature drops.

Radiation beater: Use your head. You’ve probably heard that up to 70 percent of your body heat can be lost through an uncovered noggin. While this of course depends on lots of variables, including your hairline and the clothing you’re wearing, the point is worth stressing. The scalp is well supplied with lots of heat-shedding blood vessels, and it lacks insulating layers of fat to keep that heat inside. The bottom line: Put on a hat when you start to feel chilled. Rick Curtis, director of the Outdoor Education Program at Princeton University and author of Backpacker’s Field Manual: A Comprehensive Guide to Mastering Backcountry Skills (1998; Three Rivers Press, 1-800-733-3000; $14.95) suggests choosing one with “idiot strings” that tie under the neck. “If you overheat, push it off your head and leave it tied so it won’t blow away or get lost,” he recommends.

Conduction

This one occurs when your body contacts something that’s colder than you are, like when you wrap your hands around an icy water bottle or fuel canister. The result is that the object immediately sucks heat from your body. Conduction normally accounts for about 2 percent of overall heat loss. Since water conducts heat much more efficiently than air does, wet clothes can bleed your body’s warmth up to 25 times faster than if those same clothes were dry.

Conduction beater: “Anticipate sweat production,” says Murray Hamlet, director of research plans and operations for the Army Research Institute for Environmental Medicine in Natick, Massachusetts. “If you know you’ll be hiking uphill, take off some clothes before you start. Keep your skin a little cold all the time (while moving).” The key is layering: a hydrophobic (water-hating) inner layer, an insulation layer or two, plus a windproof outer layer. “Look for clothes with zippers,” adds Curtis, “so you can vent to prevent perspiration.”

To maintain dry feet, Hamlet recommends antiperspirant. “Apply it three times a day for a week (before a trip), then once or twice a day” while backpacking. And even though we’ve said it before, it bears repeating: Shun cotton-it’s a water-retaining heat-drainer. Stick with synthetics or wool for winter wear.

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