- The Washington Times - Wednesday, February 15, 2006

Bob Klein, a Scoutmaster for 18 years, is well-versed on dressing for cold weather. On his many camping and skiing trips with the Boy Scouts, Arlington resident Mr. Klein often wears a Capilene shirt, which has polyester fibers that draw moisture away from the body, a layer of fleece and an insulated parka or nylon windproof shell.

“I would like to say everyone’s going to be dressed in high-tech gear,” Mr. Klein says a few days before one of his troop’s trips. “Some of the kids will have fleece. Some will have big jackets. Some of the smarter ones will have some sort of thermal long underwear.”

The boys in Boy Scout Troop 111 in Arlington bulked up in layers last Friday to ward off the cold while they camped overnight at Camp Highroad in Middleburg, Va. The next day, they participated in the Klondike Derby, a skills competition for Boy Scouts. They kept their heavier clothing in day packs as they pulled sleds from station to station, where they demonstrated their skills in fire building, setting up tents and applying first aid.

“They will be sweating pretty hard, and they don’t want to overdress for that,” Mr. Klein says.

Dressing inappropriately can cause loss of body heat, a byproduct of the metabolic process of burning calories for energy. The clothes may retain moisture or lack the ability to retain body heat, both of which can cool the body.

As body temperature drops, the body cannot work appropriately, and its systems slow down, with hypothermia, frostbite or even death as the end result, says Dr. Eduardo Azziz-Baumgartner, medical epidemiologist for the Centers for Disease Control and Prevention in Atlanta. The normal body temperature of 98.6 degrees Fahrenheit can fluctuate by one degree to remain within range, he says.

“The body has a limited ability to produce heat to compensate for heat loss,” Dr. Azziz-Baumgartner says.

Initially, the body begins to shiver, says Gail W. Jenkins, professor of biology, who teaches anatomy and physiology courses at Montgomery College in Takoma Park/Silver Spring.

“Every time muscles contract, that involves chemical reactions that release heat,” says Ms. Jenkins, who wrote the textbook “Anatomy and Physiology: From Science to Life,” published this year.

At a certain point, however, the body cannot compensate through shivering, says Dr. Jack Guralnik, chief of the laboratory of epidemiology, demography and biometry at the National Institute of Aging of the National Institutes of Health in Bethesda.

“Then, you’re facing hypothermia,” says Dr. Guralnik, whose specialty is epidemiology.

Mild hypothermia, which occurs when the body temperature drops to 95 to 91 degrees, can involve shivering, drowsiness, apathy and poor judgment, Ms. Jenkins says.

With moderate hypothermia, body temperature drops to 91 to 82 degrees, causing the person to no longer feel cold and to stop shivering, Ms. Jenkins says.

“You start to go into a stupor. You don’t have all of your wits about you. You’re not thinking as quickly and clearly as you would if your core body temperature were normal,” she says.

The blood vessels in the periphery of the body, such as in the fingers and toes, constrict to shunt blood to the core to protect the essential organs, Ms. Jenkins says. The heart rate, respiratory rate and blood pressure also decrease, she says.

In the case of severe hypothermia, when the body temperature is less than 82 degrees, the heart and pulse rates slow even further and the muscles become rigid and unable to relax, preventing movement, Ms. Jenkins says. The heart stops beating as the core temperature reaches 70 degrees.

Another condition resulting from prolonged exposure to the cold is frostbite, which can destroy the skin and subcutaneous tissue underneath the skin layer, Ms. Jenkins says. The affected area becomes stiff with mottled or uneven coloring. Most susceptible are the fingers, toes, ears and nose because they have a high surface-area-to-mass ratio and little muscle and fat, she says.

Wearing clothing that protects the body’s core and extremities is an important measure against hypothermia, frostbite and any kind of heat loss, metro-area outdoor recreationalists recommend.

“If you’re going to be active, use a good layering system,” says Eric Stern, assistant manager of Casual Adventure, a family-owned outdoor adventure store in Arlington. “If you’re not going to be active, that’s when you can use a lot of bulky layers that don’t breathe as well, because they can retain heat better.”

Silk and polypropylene, a synthetic nylon material, both have wicking properties to remove moisture from the skin, Mr. Stern says.

Hiker Jim Ward of Burke says he makes sure his base layer of clothing — including his bandana — is able to wick moisture.

“The idea is to stay dry. I would rather be a little bit chilly than wet,” says Mr. Ward, a member of the Potomac Appalachian Trail Club, headquartered in Vienna.

Putting fleece or down on top of the base layer helps retain the body’s heat. The amount of retention will depend on the material’s thickness and loft, or ability to trap air, Mr. Stern says.

Insulators such as Thinsulate, Polarguard or Primaloft are synthetic materials close in warmth factor to down, which has a high loft and insulation ability, Mr. Stern says.

Thinsulate, for example, consists of microfibers that are one-tenth the size of a human hair.

“The large number of microfibers in Thinsulate trap insulating air within the web and block radiation coming from your body,” says Kenneth Cox, technical service specialist for 3M, a manufacturing company in St. Paul, Minn. “Both of those methods mean your general body warmth is not transferred through the clothing, but held closer to your body.”

The top layer over the insulator typically is a shell, such as a waterproof but breathable shell that lets perspiration pass through each layer out into the air or, for high-endurance activities, a soft shell that is stretchable and water- and wind-resistant, Mr. Stern says.

“It’s a much more comfortable layer than a traditional shell,” Mr. Stern says.

Doug Braswell, store manager of the REI store in Baileys Crossroads, recommends starting with long underwear of a wool blend or synthetic materials. The underwear can be worn underneath fleece, down or a wool blend with an outer shell on top, he says.

“You have to pick and choose the kind of layer for your activity. It’s personal choice in a lot of cases,” Mr. Braswell says.

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