When properly prepared, running in cold weather can be enjoyable. Get caught without proper preparation, however, and one risks hypothermia and frostbite. The cold dry air of winter can also exacerbate symptoms of exercise induced bronchospasm, a relatively common condition in runners. Proper preparation along with a recognition of the early signs of cold related illnesses will help minimize problems associated with exercise in the cold.

While exercising in cold weather, our bodies attempt to maintain our core temperature by shunting blood away from the periphery, thus minimizing heat loss. Mild hypothermia is heralded by goose pimples and shivering as our bodies attempt to raise our metabolic rates to increase our core temperature. Moderate hypothermia will result in muscular fatigue, poor coordination, numbness and disorientation. Severe hypothermia can result ultimately in cardiovascular failure. Treatment of hypothermia requires prompt recognition and treatment as mild hypothermia can progress to a more severe situation if not addressed early. Athletes should be removed from cold, wet, or windy conditions. Wet clothing should be removed, and rewarming commenced with warm blankets and ingestion of warm fluids. If the athlete's condition does not improve, transportation to a medical facility should be arranged.

Frostbite is actual freezing of tissues secondary to exposure to the extreme cold. It most commonly occurs in the peripheral limbs and on the exposed areas of the face (cheeks, ears, and tip of the nose). Patients with superficial frostbite complain of burning local pain and paresthesias (tingling). The skin may initially be pale, but will become red with warming. Superficial blisters may be present. Superficial frostbite can be treated by local thawing. The most reliable method is direct contact with body heat (such as putting your hands in your underarms). The injured area should not be rubbed as skin sloughing may occur. Thawing should not commence, however, unless it can be ensured that refreezing will not occur. Subsequent freezing and rethawing can result in a more serious injury. Deep frostbite is initially very painful, and then tissues become numb. The affected area appears as a frozen block of hard, white tissue. Areas of gangrene may occur in severe cases. Treatment of deep frostbite includes rapid rewarming in a hot water bath. Since rewarming of deep frostbite is painful and the condition is often associated with infection, transport to a medical facility should be arranged as quickly as possible. Radiant heat (such as from a fire or radiator) should be avoided as burns may occur.

As with so many other conditions in sportsmedicine, our best offense (treatment) is a good defense (preparation!). Following the guidelines below will help minimize risk for cold related illness and will maximize our enjoyment and performance during our training runs:

1. Dress in layers of loose, lightweight clothing. The first layer of clothing (closest to the body) should be made of polyester or polypropylene which will "wick" sweat away from the body. Subsequent layers should be loose and breathable-fleece is a good choice. Cotton should be minimized as it can allow sweat buildup. The outer layer should be wind and water resistant, thus protecting from wind, rain, and snow. When in doubt, add the extra layer. You can always remove a layer if you warm up, but you will regret not having it if you start freezing with several miles to go.

2. Protect your head and extremities. Wearing a hat is essential as up to 50% of body heat can be lost though the head. Gloves are important to prevent exposure to the hands. These, too, can be removed if you get warm, but you'll regret not having them if needed. Mittens are better on colder days as they will keep the hands even warmer. Sunglasses and sunblock are important to protect the face, especially when there is glare from snow. Guys-remember to insulate the privates, which are prone to cold and frostbite. Forget this once and it will be your only time!

3. Take time to warm up and stretch before increasing intensity during training runs.

4. Remember to stay well hydrated and fed. It is easy to forget that we are sweating in the cold, and therefore we may not recognize the need to hydrate and fuel when running in the cold. Hydration and refueling are important to prevent bonking in addition to helping us maintain body temperature.

5. Plan your courses so that you can ensure staying warm and dry. Avoid courses that take you away from shelter, especially on wet windy days. Consider several shorter loops which will allow you to add or remove layers of clothing more easily or even seek shelter indoors if necessary.

6. Runners with exercise induced bronchospasm should attempt to warm air such as with a scarf or mask. A prolonged warmup prior to hard running can help minimize symptoms. Carry your inhaler if you use one, should it become necessary.

Following the above guidelines will help minimize problems associated with cold weather exercise and allow you to get the most out of your training.

Stay warm. I'll see you on the roads!

Bob Wilder, MD, FACSM

Dr. Wilder is an Associate Professor of Physical Medicine & Rehabilitation at the University of Virginia and Medical Director of The Runner's Clinic at UVa. He is Team Physician for UVa's Cross-Country and Track & Field Teams, a Fellow of the American College of Sportsmedicine, and Co-Editor of The Textbook of Running Medicine.