Many distance runners use the winter months to establish a solid base of high mileage.

Running in cold weather is possible--and even comfortable--because of the built-in protective mechanisms brought into operation by your body. Sixty-one percent of the fuel your body burns goes into heat production, and the remaining 39 percent drives your muscles.

If you exercise hard enough to increase your metabolism tenfold, you'll produce ten times as much heat but will not change this ratio of heat and muscle distribution.

When dressing for cold weather runs, it is most important to utilize a layered clothing method. This method is most efficient because air--an excellent insulator--is trapped between layers.

It should be remembered that even in the coldest weather, vigorous exercise can cause you to sweat heavily.

Regarding footwear, consider waterproof shoes. The waterproof protection will keep your feet dry and allows a breathable network for internal moisture to be released. One shoe to consider that I am using is the Brooks Ghost, which is made with Gor-tex membrane for waterproof protection.

I also find that I wear pretty much the same shoes in winter that I've been using year-round, but the shoes are sprayed with heavy-duty silicone to keep out the moisture. There is a real danger with frostbite of the feet when shoes get wet.

Here's one final cold weather running tip: Plot your course so that you run against the wind on your way out, and with the wind on your way home.

Otherwise you will form sweat on your body at the beginning of your run, and the wind will blow through your clothes on the way back, causing the sweat to evaporate and make you feel colder.

Dr. Robert Weiss is a Fairfield-native and has a sports-podiatry practice in Darien. He is a former marathon runner and was a member of the Medical Advisory Committee of the 1984 and the 1988 Olympic Trials.