Castellani was lead author of a 2006 position paper from the American College of Sports Medicine on exercising in the cold.
The big question was, Is it ever too cold Castellani said. The answer is no. People go to the poles, people are out there when its minus-50 degrees, people do incredible things, and safely. There really isnt a point where you can tell people it is not safe anymore.
Timothy Noakes, an exercise physiologist at the University of Cape Town in South Africa who was a reviewer of that position paper, even supervised a swimmer, Lewis Gordon Pugh, who swam 1 km (or .62 miles) in 19 minutes at the North Pole last July, in water that was between 29 and 32 degrees.
The problem with exercising in the cold, exercise physiologists say, is that people may be hobbled by myths that lead them to overdress or to stop moving, risky things to do.
Some worry that cold air will injure their lungs or elicit asthma symptoms. Or they are convinced that they are more susceptible to injury when it is cold and that they have to move more slowly.
But lungs are not damaged by cold, said Kenneth W Rundell, the director of respiratory research and the human physiology laboratory at Marywood University in Scranton, Pa. No matter how cold the air is, by the time it reaches your lungs, it is body temperature, he explained.
Some people complain that they get exercise-induced asthma from the cold. But that sort of irritation of the respiratory tract is caused by dryness, not cold, Rundell said. Cold air just happens not to hold much water and is quite dry, he said. Youd have the same effect exercising in air that was equally dry but warm.
Rundell and Tina Evans, a PhD candidate, showed this a few years ago in a study designed to dispel what Rundell called the myth that cold air can induce asthma. Volunteers with exercise-induced asthma, whose airways tended to narrow after exercise in the cold, breathed cold air or room temperature air that was equally dry. Their airways narrowed in response to the dryness of the air, not its temperature, Rundell said.
People with this problem should see a respiratory specialist and take medication when they exercise in dry air, Rundell said. And, he added, you might want to use a balaclava, so your exhaled breath can moisten the air you breathe.
Another myth is that you have to acclimatise to cold, just as you do to heat. Its true that peoples bodies adapt to hot weather and that adaptation makes people feel better when they exercise in the heat. It also improves performance. With heat adaptation, you sweat more profusely, your sweat is less salty and your blood volume increases.
But exercise physiologists find only modest adaptation to cold. The bodys main responses to cold constricting blood vessels near the skin, shunting blood to the bodys core and shivering do not improve if you spend more time in the cold. Nor are the physically fit any better at adaptation than the sedentary.
Right now, were not sure if there is any degree of habituation, said Robert Kenefick, a research physiologist at the Army Research Institute of Environmental Medicine.
Of course there are hazards like hypothermia. Hypothermia can happen suddenly in icy water, with the swimmers core temperature plummeting, and the fear was that Pugh might pass out and sink before he could be rescued. The biggest risk of hypothermia comes with a combination of wet and cold. That is because water transfers heat from the body 70 times more efficiently than air.
Hypothermia begins to set in when the bodys core temperature falls to 95 degrees. That elicits shivering and a rise in blood pressure. But if your temperature drops to 85, you lose consciousness, and if it goes much lower, you can die. The trick to avoiding hypothermia is to keep moving, Noakes said.
One mistake winter exercisers make is wearing too much clothing. You dont want to sweat profusely because you overdressed. You should feel cool before you start exercising, Castellani said. You should not feel comfortable. That means, Noakes said, that even in temperatures as low as 10 to minus-20 degrees, a runner probably needs to wear no more than a track suit, mittens or gloves and a hat.
NY Times / Gina Kolata