It's bitter cold outside. You want to go for a run but you need that little push to get you out the door.

You can do it. You just need to know what you're getting into and be prepared with the right stuff.

To stay alive, people must maintain a core body temperature between 75 and 105 degrees. When runners are out in the cold, their bodies will naturally shunt blood toward the critical core and away from extremities. To produce heat, your body will react by shivering. Running will also produce heat, but it may not be enough for persons with low body fat or those who are not hydrated enough.

Two major concerns for runners out in the cold are hypothermia and frostbite.

Hypothermia is a lowering of core body temperature. In mild form you would experience uncontrollable shivering. If core temps continue to drop, shivering stops and you lose coordination. In its severe stage, you experience a loss of reflexes, lack of pain and possibly go into a coma.

Hypothermia can also set in after you stop running, making it important to find a warm place and change into dry clothing.

Two ways to help prevent hypothermia are to run into the wind first and come back with it after you've worked up a sweat. Or have someone drive you out so you can run to your finishing point entirely with the wind.

Frostbite results when skin is exposed to the cold for a long time and blood flow is reduced to your extremities such as fingers, toes, ears and nose. Usually you are so numb you don't notice it. In its true form, people suffer irreversible loss of tissue. In its worst form, you skin creates deep- purple blisters. If the bone freezes, amputation is required.

Now I have freaked you out, there is good news. By layering many of today's latest clothing materials, neither of these circumstances should occur while you're running in sub-freezing temperatures.

The key is layering the right clothing and not overdressing to the point of excessive sweating.

In moderate cold (40 to 50 degrees), one layer is probably adequate. Long-sleeve t-shirts, Lycra lightweight tights and maybe a baseball cap.

In chilly temperatures (25 to 40 degrees), two layers are helpful. Start with an under layer of synthetic fibers such as polypropylene, Coolmax or Thermax in long-sleeve t-shirts, plus heavier tights. Add a lightweight Goretex or windbreaker jacket, plus hat and gloves.

In freezing-cold weather (10 to 15 degrees), try three layers. There are a number of new materials in hats and gloves to use in these temperatures: the best are those that wick away moisture. Try an inner glove topped with a mitten to protect your hands. A balaclava and additional neck covering may be necessary.

To prepare for cold-weather running on snow-covered or slushy pavement, make sure you use something other than cotton socks to wick away moisture. Try double layering socks, but only after you have purchased a pair of shoes that have room for them. Sun block, moisturizers and Vaseline are excellent products to protect your skin, not only from frostbite but to prevent that weathered, worn look.

Finally, a reminder to wear light-colored or reflective outer layers, especially when running in snowfall or dark conditions near motor traffic.

Livonia's Doug Kurtis is no stranger to winter running. He holds world records for the most sub-2:20 marathons (76) and marathon wins (40). He may contacted at dkurtis@earthlink.com. MR