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When is it too cold to exercise outdoors?

Estimated read time: 7-8 minutes

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The solstice draws nigh. The dark closes in on morning and night. The temperature settles below freezing and shows few signs of budging.

What easy, convenient excuses for putting an outdoor exercise routine on hiatus. But should you? Consider your options:

1. Put another log on the fire, crawl under the blankets and make like a bear, hibernating until spring. Few people would take you to task; it would probably be their first instinct, too.

2. Take your workout indoors, at a health club.

3. Or you could take a stroll or jog, as did Robert Frost, on the road less taken. The one sparkling from an early frost, as yet untouched by man or beast. The invigorating air jump-starts your brain and body as it hits your lungs.

Winter gives you a chance to try a different sport, such as cross-country skiing or snowshoeing. A day of sleigh riding, especially the time spent trudging the sled UP the hill, will give you quite a workout.

You can also just stick to your favorite exercise, as does year-round cyclist Tanya Wolff, an assistant professor in Washington University's genetics department. She took up cycling to work and for pleasure more than a decade ago in California, "long enough to get spoiled" she said, by the favorable climate. The move to harsh St. Louis winters took a little getting used to.

In addition to commuting, Wolff said she rides in the winter "for pleasure, though you may wonder why it's pleasurable when it's 10 degrees." Her favorite spot is the Berryman Trail, a 24-mile loop through the Mark Twain National Forest about 15 minutes south of Bourbon, Mo.

"It's so much fun that it's worth doing it," she said. "Riding in the woods, there's no windchill. The solitude makes it so peaceful out there. Technically, it's challenging because of the ravines. With the snow, it's pretty."

Tom Wiltsch, a former vice president of the St. Louis Track Club, also welcomes winter.

"I'm a heavy sweater, so those summer runs are tough on me," Wiltsch said. "I feel less fatigued in the winter."

Other die-hards say extreme winter weather is a way to test a runner's commitment. You find a sense of quiet superiority among year-round runners. In fact, the St. Louis Track Club sponsors races it has dubbed the Frostbite Series for those who want a reason to get outside and be smug about it.

The rewards for the well-prepared adventurer are more than worth the effort. Well-prepared, however, is the operative phrase.

"Exercising for health is a controlled stress on the body," said Dr. Michael Cannon, a family practitioner specializing in sports medicine at SLUCare in Des Peres, Mo. "We don't want to increase the stress to the point that we're harming our well-being. When we exercise out in cold, we're adding another stress, so we're increasing our chances of not controlling the stress and causing harm."

Here are the major dangers of exercising in the cold and ways to control the stress:


Hypothermia is reduced body temperature that can cause death. Symptoms include confusion, drowsiness, slurred speech, a drop in blood pressure, shallow breathing and a pinkish tint to the skin.

The key to preventing it is to think of yourself as a triple-layer chocolate cake.

The layer closest to your skin should be a synthetic. Look for polypropylene, or fancy name brands such as ColdGear, Dri-Fit or Coolmax. The base layer should act like a wick and take sweat from the skin to the outer side of the fabric, "where it doesn't touch your skin," Cannon said. "Dry skin stays warmer."

A second layer should be synthetic or wool. The third layer, on the outside, should be wind-resistant, which is a major issue for cyclists. High-end fabrics such as Gore-tex fill the bill, though nylon works well for those on a budget.

"Any air moving across your body will cool you in a big way," Cannon said. "But if you can hold the sweat in the middle layer and keep the layer closest to your body dry, you keep your body heat."

Wiltsch and serious runners tend to wear shorts until the temperature gets into the 30s. A further drop brings out tights, which come in differing degrees of thickness. Some are made of the wicking materials listed above and can be paired with nylon or Gore-tex pants on extremely cold days.

Avoid cotton like the plague. Unlike synthetics, cotton keeps moisture close to skin. Wet skin becomes cold skin, which reduces body temperature and can bring on hypothermia.

Another danger of hypothermia comes when someone overdresses and sweats too much in the process.

"Be comfortable 20 minutes into the run," Wiltsch said. "If you get sweaty, you'll get cold. You're asking for trouble."

The first sign of reduced body temperature, Cannon said, is "someone who feels cold but is no longer shivering. He has a problem that's significant because his body isn't responding as it should."


Extremities are at risk because of one of the body's survival techniques. In cold weather, your body wants to keep its core and vital organs warm. So, when push comes to shove, the midsection hogs most of the blood flow, reducing the supply to feet, hands, ears and nose. Reduce the flow enough, and the extremities freeze. Many people are unaware of the onset of frostbite because their hands and feet are numb from the cold.

There are two types of frostbite. The superficial type, called frost nip, is reversible because it affects the skin only. The skin appears waxy and white. In deep frostbite, purple blisters appear.

The best way to prevent frostbite is to cover everything: a ski cap or earband on the head, gloves or mittens on the hands. Cannon advocates wearing two pairs of socks, though Wiltsch prefers the double-layer models because they also prevent blisters.

Wolff said feet get colder than any part of the body on a winter ride. Cyclists wear a heavy neoprene cover over their shoes, "and sometimes that's still not enough to keep your feet warm," she said.


Often, the risk is higher in winter. When people sweat, they can see that they've lost water and are apt to replenish it. But, as Cannon noted, "with lower humidity in winter, we lose more water through the water vapor in our breath. But we can't see the water we're losing through breathing. So dehydration in the winter is a sneaky danger."

Those who overdress also are prone to lose more fluid than they are aware of. Drink before exercising and every half-hour or so, just as you would at any other time of year.


Roads narrowed by snowpack means less space for runners, cyclists and drivers to share. Often, exercisers are forced into lanes of traffic.

"People are not expecting to see bikes on the road in the cold," Wolff said. "The cyclist is the one that stands to lose the battle, so we have to drive much more defensively."

Ice and snow reduce the traction of tires and shoes, making falls more prevalent. To combat this, runners and walkers can buy crampons that dig into ice and snow, improving traction. In addition, try slowing your pace and shortening your stride.

Cyclists can deflate their tires a bit, which improves grip. Many put away the road bikes, with their skinny tires, and switch to mountain bikes, even if they're commuting to work.

In addition, the shorter days mean that more exercisers wedded to morning or evening runs are forced to run in the dark.


When the temperature difference between the air outside and inside our lungs approaches 100 degrees, the air entering the lungs can't be fully warmed or humidified, which can cause coughing spells or bring on an asthmatic attack.

Which brings up the question of whether there's an absolute temperature for when it's just too cold. When is it time to work out indoors or take the day off?

Wiltsch said he runs until the temperature drops into the single digits. "It really helps if the sun is out, though," he said. "I just feel warmer and more energetic."

Cannon noted that the more important number is the windchill factor.

"Very few people exercising for health should be out there below a windchill factor of zero," he said. "You're not pursuing something that's healthy. We lose the forest for the trees. If we're talking about health, there's nothing healthy about it."

A cyclist traveling at 15 to 20 mph creates his own windchill, or adds to the existing factor. Wolff lives about nine miles from work and remembers her coldest commute, on a day when the temperature was zero with a minus 20 windchill.

"That may be my cutoff," she said.


(c) 2004, St. Louis Post-Dispatch. Distributed by Knight Ridder/Tribune News Service.

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