GRAND BAHAMA ISLAND -- I shouldn't tell you this, but I'm in my hammock, pad in hand, basking in the island sun filtering through the banyan tree. It's 78 degrees, our low for the day. As winter approaches, the low may get down to 68. Brrrr.

A reliable source tells me it gets much colder in the D.C. area, which in all likelihood will discourage your fitness pursuits, right? And probably tempt you to settle into your recliner, flick on the TV, and watch someone else do the running and exercise for the duration of winter, right? In your heart you know that giving in to such temptation leads straight to a new wardrobe in larger sizes next spring, the creeping fat syndrome.

Which means you must exercise in the cold, move to warmer climes or be a little more innovative and careful in your workout routines. Whichever, I hope these suggestions will make your workouts a little more livable.

Exercising Safely in Cold Weather First, dress properly for cold weather. Whether you are walking, jogging, biking or simply playing a sport, wear layers of light clothes rather than one heavy garment. Layers trap warm air better and allow you to peel them off as needed as you warm up.

Since you lose a lot of heat from your head, remember to wear a cap. A cap (or earmuffs) also prevents frozen ears and the intense ear pain that many people get when they run or bike in cold weather. Gloves or mittens will do the same for frozen hands.

You may think you look funny loping along the canal path in short pants, hat, and mittens, but personally I wouldn't mind looking like Opus at a Halloween party if it prevented frostbite.

Dehydration, interestingly enough, can also be a problem in cold weather. We're used to thinking "Drink plenty of water" in hot weather, but may fail to do so when the weather is cooler because we aren't sweating as much. But as cold air is breathed in, it's warmed by the trachea and lungs and it draws moisture from these tissues. That's why you get that raw, dry feeling in your mouth and throat when you run in cold weather. So remember to drink cool water before and during exercise even in winter.

If you're still swimming in an outdoor pool, remember that water cooler than body temperature draws heat away from the body. Consequently, swimming in cold water produces prolific heat loss even when exercising vigorously.

Even 80-degree water quickly drains heat from your body. But 60-degree water -- and a lot of pools get colder than that -- can put you in shock in minutes.

If your outdoor pool is heated, the temperature of the air above it makes no difference. But if your pool is not heated, the water may still be too cold even on a balmy fall day in the high 60s. Consider getting a "shortie" wet suit from a scuba shop. Shorties don't have arms or legs, but keep you warm enough to keep on swimming for many extra weeks. Get a 3/8- or 1/4-inch suit, depending on your chill factor.

Other Winter Cautions Because winter days are shorter, many of you have to exercise after dark. And too many of you do it in the road without adequate safety gear. I almost made an angel of a young woman wearing a blue sweat suit while she jogged in the road the other night. Please run off-road on sidewalks and jogging paths if possible and always wear a reflective vest. If you bike, don't count on your pedal reflectors to protect you, either. Buy a vest and wear your helmet.

If you have any type of heart condition, even if your doctor has said it's okay to exercise, make sure it's okay in really cold weather. Several studies show that breathing cold air promotes chest pain in some people with existing heart problems.

Take It Indoors If all this makes your favorite chair ever more enticing, move your workout indoors, at least on the very coldest days. Here are some ideas.

Try mall walking. Some shopping malls are even sponsoring "mall walkers" by opening the center before stores open. But you don't need a special program to put in a few miles after work. Just leave the wallet and credit cards at home.

Try stair climbing. Stairs give you a great aerobic workout, though the scenery can be a little dull. Any building two stories tall or higher usually has the equipment. In shorter buildings you can walk a stair and hall circuit -- up the stairs, through the hall, down the second set of stairs, through the hall, repeat. In taller buildings you can add flights.

Join a gym for the winter. Many gyms and fitness centers offer membership on a monthly basis. You can get in your aerobic workout on the treadmill, stationary bicycle or indoor pool. And why not muster up the courage to try an aerobic dance class? Most groups offer classes designed specifically for winter dancers.

Get a workout in the water. Even if you don't swim, you can get a great workout in a pool. Here are several exercises that you can try in waist- to chest-deep water:

Stride Hops. Standing with your hands on your hips, jump up slightly and come down with your left leg forward and your right leg back. Jump up again, reversing position of legs. Try to move your legs as far forward and backward as possible. Work up to two minutes of continuous hopping.

Toe bounces. Hold on to the edge of the pool if you need to steady yourself, and stand on your toes. Repeat. Gradually increase your upward push until you are bouncing off the bottom. Work up to two minutes.

Walking twists. In waist-deep water, with your fingers laced behind your neck, walk forward and twist your body, touching your left elbow to your right knee, right elbow to left knee. Raise your knees high enough that your face doesn't go under water.

Standing crawl. This is a standing version of the swimming crawl. In chest-deep water, reach out with your right hand and pull it through the water as deep as possible. As your right hand reaches your thigh ready to be pulled out, your left hand should be entering the water.

Don't quit with these exercises, either. Use water as a medium to duplicate any movement. If you like to dance, do it in water and increase your work level. Are you a jog-walker? Do it in the shallow end of the pool. Be creative.

And when you want to learn more water exercises, get a copy of Aqua Dynamics, a booklet published by the President's Council on Physical Fitness and available from the Government Printing Office (Washington, D.C. 20402-9325) for $3.75, stock No. 040-000-00360-6.