"You can exercise safely in any kind of weather," says Diana Nyad, "as long as you take certain measures to accommodate yourself to extremes in temperature."
Among her suggestions for cold-weather training:
* Dress right. You're going to perspire no matter how cold it is outside, so layer your clothing and peel off outer layers when you get too warm or add as a shield if a wind comes up. Try: polypropylene undershirt, short-sleeved T-shirt, thin cotton turtleneck, sweater (optional) covered with parka or windbreaker. Wear a flat-knit 100 percent wool hat, down mittens with silk-glove liners and thin inner socks overlaid with wool socks.
* Minimize chill. Map out your route so you're facing the wind at the beginning of a run, and have it at your back on the way home.
* Eat wisely. You need more calories during cold weather. Carbohydrates such as natural fruits are preferable to simple sugars like candy. Avoid drinking liquor outdoors. It doesn't warm you up -- it just seems to -- and can dull your senses so much you'll fail to recognize warning signs of cold-weather hazards.
* Recognize warning signs. A body part suffering from frostbite looks white, feels hard and rigid, is painful at first and then numb. Thaw the area in warm water at 100 to 108 F, but not above 112 F. Hypothermia occurs when body temperature drops dangerously below normal, and can result in death. Warning signs include slurred speech, loss of coordination, skin redness, shivering and confusion. Raise the temperature with blankets, other people's warm bodies or a warm bath.