Don't let winter run you down. (New Year's Resolutions).

January brings an unfortunate coincidence for "lapsed" runners: New Year's resolutions, replete with their high hopes of again establishing a running program, coupled with the least pleasant weather in which to find yourself outdoors. Still, there are new reasons every day to train throughout the colder months. What was once an excuse to wait until spring looks now like a reason to get out into the cold.

If you're prone to respiratory infection, winter can be a time of increased vulnerability. Whether viral or bacterial in nature, these illnesses range from the mild sore throat or common cold to debilitating bouts of influenza or bronchitis. However, several studies show that moderate physical activity may improve the immune system and reduce the risk of both upper and lower respiratory infection.

The adaptive immune systems of 10 competitive cross-country skiers were recently compared to 10 moderately trained skiers and 10 untrained healthy controls. Similar to winter running, cross-country skiing is an outdoor, cold-weather pursuit. Over the course of two months. moderately trained cross-country skiers showed a significantly increased production of interferons. These glycoproteins are instrumental in fighting viral infections and are therefore associated with a stronger immune system. The controls did not experience any such increase. Interestingly, the T-cell counts of the competitive skiers decreased, the weakened immunity being attributed to repeated bouts of intense exercise. The data suggests that the immune system benefits most from moderate endurance training.

Another investigation examined differences in upper respiratory tract infection (URTI) risk between 547 physically inactive and moderately active healthy adults aged 20 to 70 years. They reported URTI events at 90-day intervals for one year. Adjusting for a number of potential confounds including age, anxiety level and diet, URTI risk was reduced by about 20% in those who maintained a moderate level of exercise. Similarly, a third study showed that moderate physical activity in older adults lowered the risk of both upper and lower respiratory infection. The unreliability of many self-diagnosed URTIs has contributed to the controversy surrounding the link between exercise and increased immunity, however, and more research is needed.

If your New Year's resolutions have you energized for a fresh crack at the roads, here are some tips to get you started and, more importantly, keep you going.

Dress down. Try to avoid piling on excessive layers of heavy clothing. You should feel chilly at the outset of any cold weather run. You will generate heat along the way, and soon enough become surprisingly comfortable in your environment. Just try to remember the upwind legs of your route will always feel much colder than the downwind legs. Avoid cotton garments on winter runs; they retain water, which conducts heat away from your body much faster than air. Wool, on the other hand, wicks sweat away from your body and retains heat even when wet. Synthetic fabrics such as fleece offer a lightweight way to keep moisture at a minimum, and consequently warmth at a maximum. See Running & FitNews, Dec 2001, for more details on layering clothing.

Slow down. Ice accumulates in shaded areas, so run with caution. Road space is limited when plowed snow accumulates, and cars have decreased visibility with less daylight and frosted or foggy windows. Fall back on an indoor exercise when the weather tells you running outside is foolish. Remember at some temperatures, bundling up will be necessary. Expect a sluggish running pace under all the layers. You'll feel and run encumbered, which will decrease your flexibility. The cold weather itself will contribute to muscle stiffness that makes injury far more likely than in warmer months. So be sure to warm up thoroughly and carefully.

Cool down. Walk and stretch for several minutes after completing a run. If it's truly arctic in the great outdoors, devote 10 minutes to stretching indoors, giving those muscles all they need to make tomorrows run easier.

Drink up. Remember heat isn't the only factor contributing to dehydration. Your body loses water vapor through respiration. Don't take the fact that you are sweating less (and aren't thirsty) as evidence that you aren't losing fluids. Drink as you would in warmer weather--dehydration will lower your immune system. If you're feeling under the weather, listen to your body. Some runners find that at the onset of a cold, running can often counter the lethargy they feel. ARA Editorial Board Member Randy Eichner, M.D., uses a "neck check": if symptoms are from the neck up, give it a try. If necessary, cut your mileage in half. Below-the-neck symptoms like a deep cough or general aches mean rest. And don't run with a fever; heart inflammation and other complications can occur.

Sign up. If you're shy about stepping out in the brisk winter months, use a race as a winter support group. If you've signed up, you'll show up. You can literally get a lot of mileage out of the fact that you'll want to train for the race or you'll feel miserable running it.

Lighten up. Don't expect too much from your winter race times. A 20 m.p.h. headwind will cause a 10:00 miler to lose 60 to 90 seconds per mile, and an 8:00 miler to lose 45 to 60 seconds per mile. Conversely (and perhaps cruelly), an equivalent tailwind's benefit will only be half the time-cost of such a headwind. Avoid injury, and use the new year as a chance to re-examine your fitness priorities. If you're still sticking to your January resolutions in March, by April you'll be shedding minutes off that 5K time, like so much winter clothing.

(Alberto Salazar's Guide to Road Racing by Alberto Salazar with Richard A. Lovett, McGraw-Hill, Blacklick, OH, 2003, 286 pp. $16.95; Med. Sci. Sport Exerc., 2002, Vol. 34, No. 8, pp. 1242-1248; Int'l Journal Sports Med., 2001, Vol. 22, No. 1, pp. 52-59; Home Care Provider, 1998, Vol. 3, No. 1, pp. 41-46)