With cold weather, icy streets and shorter days, it’s easy to find an excuse to stay inside during the winter months. That’s presumably why Americans on average get about half an hour less daily physical activity at this time of year.
But not everyone has a choice. Elite winter athletes and military personnel in northern postings stay active no matter how low the mercury drops — and the scientists who work with them continue to learn new things about how to do so safely, effectively and even comfortably.
Here’s what their latest findings can teach the rest of us about staying active outdoors through the winter.
You will get used to the cold.
The good news is that your perception of temperature changes with the seasons. “When we get that first bit of cold air, it feels awful,” said John Castellani, a physiologist at the U.S. Army Research Institute of Environmental Medicine in Massachusetts. “And then in March, you get that same temperature and it feels like it’s time to go play golf.”
These changes start happening within about ten days of exposure, Dr. Castellani said. But they’re only skin deep: You feel less cold, but for the most part you don’t get any better at keeping your core temperature up or your extremities warm.
Military researchers have gone to great lengths trying to help soldiers adapt to winter weather, with little success. A few people — the polar swimmer Lewis Pugh, for one — have demonstrated extraordinary cold tolerance, but they seem to be outliers. “I don’t dispute what they can do,” said Stephen Cheung, an environmental physiologist at Brock University in Canada. “But I don’t think there are lessons that we can learn from them and apply to ourselves.”
In one of Dr. Cheung’s studies, volunteers dunked their hands in 46-degree water for half an hour each day. After 15 days, their fingers felt less cold during the test. But their skin actually dropped to a lower temperature, a paradoxical response that could inadvertently raise the risk of frostbite. The takeaway: Even in March, when the cold feels less biting, keep dressing appropriately.
Winter workouts really are harder.
It simply takes more energy to sustain a given pace in the cold, according to a new analysis by Dr. Castellani and his colleagues. That means exercise feels harder and raises your risk of hitting the wall or getting dehydrated during long workouts.
That’s partly because your muscles don’t work as well when they’re cold, meaning that you have to recruit more muscle fibers for longer to generate a given force. But there are also more prosaic reasons. Winter clothing and footwear are heavier, and there’s added friction between clothing layers. On slippery surfaces, Dr. Castellani noted, “even the act of trying to walk gingerly increases energy expenditure.”
Add up those contributions, and you might be burning 10 percent more energy during a winter hike or bike ride than you would in warmer weather, Dr. Cheung said. That means you should adjust your pace and expectations accordingly.
Just feeling cold might hurt your performance, too. Dr. Cheung has found that standing around in workout clothes in 32-degree air ahead of a cycling test lowered endurance by 30 percent. That’s a good argument for staying warm until the moment you’re ready to start exercising.
You won’t actually freeze your lungs.
Your airways are fully capable of warming even Arctic air before it gets to your lungs. But there’s a closely related problem.
“Cold air is always dry air,” said Michael Kennedy, an exercise physiologist at the University of Alberta who has worked extensively with cross-country skiers. The amount of moisture that air can hold halves with every 20-degree drop in temperature; when you get down to 5 degrees, the air is essentially moisture-free. That dryness irritates your airways, especially if you’re breathing hard for a prolonged period.
As a result, many winter exercisers experience respiratory symptoms like wheezing, coughing, excess mucus and chest tightness during and after workouts. And it’s not just athletes, Dr. Kennedy pointed out: As many as one in five people among the general population report similar symptoms.
The best countermeasure is covering your mouth, which slows airflow and recaptures some of the moisture in your exhaled breath. Dr. Kennedy wears a thin merino-wool balaclava for subfreezing workouts, and switches to a specialized breathing mask when it dips below 15 degrees. A simpler alternative is to wear a neck gaiter and rotate it periodically as it ices up.
Wear a hat. (And a coat!)
In the 1950s, researchers found that about half of your body’s natural heat production could escape through your head if you didn’t cover it. That factoid remains a staple of parental advice, though Dr. Castellani pointed out that the subjects in those studies were wearing winter clothing on the rest of their body. You can’t just walk around naked with a hat on and expect to stay warm.
Your body does pump a disproportionate amount of warm blood to your face and head to keep your brain warm. In one of Dr. Castellani’s studies, covering the face with a balaclava and goggles kept volunteers’ fingers slightly warmer and more comfortable. But other research has suggested that keeping your core warm is another key to keeping your hands and feet from getting cold. In other words, you need a whole outfit, not just a great hat, nice mittens or a puffy jacket.
Still, there’s an unavoidable truth about winter workout attire, Dr. Cheung said: “You can’t be properly dressed for both standing around and for exercising.” If you’re comfortable standing around, you’ll overheat when you start moving. Once you start sweating, your damp clothing will leak heat up to twice as quickly — and you’ll have the unpleasant “hydrosensation” of wet fabric against your skin.
The secret to a successful winter workout, then, might be to accept five minutes of initial discomfort, knowing that you’ll feel better once you warm up. In some ways, that’s a better deal than muggy midsummer workouts, Dr. Cheung said.
“You can only take off so many clothes in the heat,” he pointed out. “In the cold, you can put on as many layers as you want.”
