It's OK You Can Play When It's Cold Outside
Dr. Donald Kirkendall
For Active.com
Exercise in the cold presents a smaller risk for injury than exercise in extrememe heat due to brief exposure, nearby shelter, protective clothing and the heat generated during exercise. There is more risk to exercising in the heat because we operate much closer to our boiling point.
Spectators at cold-weather events have more of a problem than the athletes. Cross-county skiing races have been contested at temperatures approaching minus 30 degrees F with no trouble for the athletes--not so for race officials and spectators.
In the cold, the body tries to preserve heat. Blood vessels in the skin narrow, diverting blood from the cool skin to the warmer depths of the body. Shivering--alternate coordinated contractions of opposing muscles to generate heat--is a protective mechanism. Hormones that elevate the metabolic rate--and thereby body heat--may be released. The most obvious response, goosebumps (piloerection), produces insignificant amounts of heat.
Layering clothing can help control heat when it comes to exercise. The closest layer to the skin should wick sweat away from the skin. Each additional layer traps a little air that is warmed by the body and helps keep us comfortable.
The layers nearest the skin should be as dry as possible. Any trapped moisture exposed to the cold will make us colder. As for the spectators, I am always amazed that news programs tell spectators to "layer up'" before going to watch a game in the cold. Any hunter knows that when you sit in the cold, wear a wicking garment next to the skin, then bulk up. A spectator who layers clothing like the athletes will get cold.
Athletes rarely need more than four layers on their torso and two on their legs, then gloves and a hat. If possible, the outer garment should have a zipper or button front. Adding or removing hats, gloves and opening or closing the outer shirt can control body temperature quite well. As a rule of thumb, dress for exercise as though the outside temperature was 10 degrees F warmer than it really is.
Some common questions about cold-weather exercise:
Can the lungs ever freeze when exercising in the cold? No. The air warms very quickly on its way to the lungs.
How much heat is lost through the head? The lower the temperature, the greater the heat loss through the scalp. At rest, about 30 percent of body heat is lost through the head. During exercise, about 19 percent of heat loss is through the scalp. When out training or jogging, use a hat to keep heat in, and carry it as you get warm.
Is performance decreased in the cold? Exercise in cold air does not seem to have any affect on performance. Actually, for some endurance situations, working in the cold is better because the body doesn't have to work as hard at ridding itself of heat.
What is wind chill? The wind chill index represents a rate of cooling on exposed skin. The greater the wind chill, the faster the exposed skin will cool. For most people, the only place wind chill is felt is the face, as the rest of the body is covered. Most wind chill charts show little danger when the air temperature is 20 degrees F or greater.
Danger zones begin when the wind-chill index is minus 20 degrees or less. In the Southeast, we have little concern for this; our New England or Great Lakes relatives, on the other hand, do. The legendary 1967 "Ice Bowl game in Green Bay was played in wind chills of around minus 50 degrees F.
If the temperature is above freezing, wind chill is not an issue regardless of what the weather forecaster says. If it is 40 degrees F outside with a wind chill of 20 degrees F, water will not freeze, neither will your skin.
What about hypothermia and frostbite? Hypothermia is a condition when the core temperature is 95 degrees F or less: a medical emergency. Frostbite is when the skin freezes. There is the threat of frostbite when the air temperature is 0 degrees F and a wind speed of 10 mph or greater. For flesh to freeze in one minute, the conditions need to be very severe like minus 43 degrees F with a 10 mph wind.
What affects our tolerance to cold? One factor is body surface area to weight ratio. The smaller person requires more heat to maintain temperature than a large person. Fat is a natural insulator. Young adults are more tolerant of cold than older adults, but children are less tolerant of cold than adults. Fit people are more tolerant of the cold.
Who is better in the cold men or women? If all factors are equal--body surface area/weight ratio, age, fitness, body fat levels, energy expenditure--there is little difference between men and women for skin and core body temperatures.