Cold Weather's Coming: Is Your Body Ready?

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In November, Prince Harry plans to walk 200 miles to the South Pole as part of a race for charity with disabled veterans. To prepare for the trek, he recently spent 20 hours in a special chamber that was cooled to 30 degrees below zero. Inside, the prince and his team exercised and slept as manmade winds gusted up to 45 miles per hour.

Harry's long night in the freezer may have offered some mental benefits, giving him practice with his gear and confidence that he will be able to survive the trek. But, experts said, enduring one night of cold months before a sub-zero event is unlikely to help anyone’s body prepare for an extended adventure near the poles.

In fact, studies show that it often takes weeks for our bodies to adapt to cold temperatures. Even then, the human body is far worse at acclimatizing to frigid conditions than it is to heat or altitude.

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"Ultimately, we are a heat-adapted species," said Josh Snodgrass, an anthropologist at the University of Oregon, Eugene. "Even populations we think of as quintessentially cold-adapted, like Siberians or the Inuit, are not that far removed from human ancestors that adapted to heat. Our bodies are just not as good at dealing with cold."

Anyone who lives in a seasonal climate goes through the adjustment process every year. After a long, hot summer, the first few chilly days of fall are a shock to the system -- and the feeling is only partly psychological.

When you're not yet used to cool temperatures, your body reacts in several ways. First, it shivers, which is a useful -- if uncomfortable -- way of generating warmth. At the same time, blood vessels that lead to the extremities constrict as the body prioritizes sending blood to the core and keeping the essential organs warm. The result is cold fingers that don’t work as well as they should and aching toes that feel like ice cubes.

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Over time, and that generally means several weeks, the human body adjusts to cold by dulling the shivering response. It also gets quicker at finding a balance between vessel constriction and dilation, allowing both the core and the outer shell of the body to stay warm. This process of habituation helps explain why temperatures that seem shocking in November can actually feel good in March.

Lab experiments -- along with studies of surfers, long-distance swimmers and people who live subsistence lifestyles in extremely cold places -- show that the human body can also adapt in deeper ways when exposure to cold is extreme and long lasting.

After enough time in the cold, for example, resting metabolism ramps up to a higher level so that the body produces more heat. In people exposed to the most extreme chills, like pearl divers in Korea and Japan who regularly plunge into waters as cold as 50 degrees F without a wetsuit, the body actually refines its ability to insulate itself by redistributing heat.

"That's hard to develop and takes a lot of repeated exposures," said Michael Sawka, a physiologist at the Georgia Institute of Technology in Atlanta.