You've probably grown so accustomed to seeing people running and cycling through your neighborhood that it might come as a surprise that virtually every major fitness poll consistently ranks swimming as America's most popular participatory sport. Not only are more people swimming in an increasing number of backyard and community pools, but athletes from other sports are finding it a great way to maintain their conditioning during the off-season, to rehabilitate injuries and improve flexibility.

With 102 million adult participants, swimming is "the nation's favorite leisure time activity," reported a 1982 Nielson study of sports participation. Swimming also led the 1984 sports census taken by Sporting Goods Dealer magazine, with 96 million adult participants.

On the physical side, regular swimming produces the benefits associated with any aerobic exercise: improved cardiovascular fitness, a more efficient heart, reduced blood pressure, and so on. Plus, it adds a few touches of its own.

Since swimmers are horizontal in the water, the heart doesn't have to pump against gravity as it would during running. This makes swimming an excellent exercise for those who are out of shape or beset by circulatory problems. The elderly and people with joint problems often find water's suspension properties particularly forgiving.

Add to that swimming's low injury rate, its kindness toward tight or aching joints and its "sensory deprivation" trance, and you have a sport elevated beyond what the land-locked might dismiss as monotony into a floating meditation.

You've heard a lot about the physical and psychological benefits of exercise, and swimming may excel at the latter better than anything else going. Some suggest that rolling around in a liquid environment, surrounded yet weightless, is as "back to the womb" as one can get. Not so farfetched when you realize that water, whether it's a lakefront or a drive along the ocean, is keenly associated with "getting away from it all."

Consider also that the U.S. space program, back in the 1950s, did research on the effects of long periods of time spent with little sensory imput. When volunteers were placed in flotation tanks in completely dark, soundproof laboratories, scientists expected brain activity to shut down in the absence of external stimuli. Instead, to their surprise, many of the volunteers reported vivid sensory flooding. When unburdened, the mind could come alive on its own.

Pool swimmers experience silence, monotonous visual surroundings, the steady and lulling rhythm of stroke and kick, and a profound weightlessness -- a marvelous, hypnotic refuge.

Having sung the Zen praises of the sport, one should -- as with any earthly enthrallment -- enjoy the ineffable qualities but not be blind to the more mundane truisms.

For example, contrary to popular thought, swimming is not the best overall sport going, and its very meditative allure can give the illusion of fulfilling basic aerobic requirements when in fact you haven't pushed as hard as was necessary to achieve aerobic benefits. Water can impart a lingering briskness and refreshment that is sometimes exclusive of getting the pulse rate up into the proper range.

As for the "total body exercise" myth, if you're using your arms and legs equally, it's a good indication that your stroke is way off-base. Your legs should be kicking in a steady rhythm, with the lion's share of propulsive power coming from your arms and upper back. Cross-country skiing is much more of an "all-around" winner, since it puts upper- and lower-body strength practically on parity.

There are plenty of other myths about swimming, too, such as the belief that it's a super calorie burner. Actually, it isn't as high-octane a fat-fighter as running.

Also, most people assume that if you're able to swim farther and farther, it means you're getting better and better. But increasing yardage each week or month doesn't necessarily mean you're improving. As your piano teacher probably warned you, imperfect practice only leads to imperfect performance. You do not "iron out" mistakes as you go along.

Instead of working on distance, you must work either on speed or technique to train your body to get more efficient. Rather than slopping along for 40 minutes instead of your usual 30, it's better to cut down to 20 minutes and swim faster or to concentrate on improving your stroke.

Since swimming relies so heavily on technique, in fact, mindless tacking on of distance might lead to slower times. It's a good idea to have two swimming goals: short and fast, and long and slow. The short and fast swims help your body increase its ability to use oxygen efficiently; the long and slow teaches your body how to burn its fat more efficiently.

Keeping Count

One of the biggest blocks to achieving fitness goals -- through swimming or any exercise -- is boredom. An activity that starts out as fun may lose its luster after several weeks of workouts.

But there are a number of tricks of the swimmer's trade to make you remember why you fell in love with the sport in the first place.

For example, let's say you've been swimming for a few months now, loping back and forth during the "open swim" times at your local pool. You put in 20 (or 50 or 80) lengths at a time -- or fairly close to that, anyway, because frankly it's easy to lose count and let the water lull you into a sense of "automatic pilot." You hate to admit it, but you're getting a little bored, not to mention frustrated, because your swimming is going nowhere.

One good motivator -- for the beginner or the veteran -- is to sign up for swim lessons at your local Y, community or college pool. Classes are often sponsored for all levels of skill. Technique is so crucial to swimming that you'll save yourself a lot of backtracking and grief by learning proper arm-and-leg coordination at the outset.

Most beginning swimmers make the mistake of flailing away fast and furiously instead of maximizing stroke efficiency. How you cover those 50 lengths is every bit as important as struggling along.

Watch world-class competitors in the pool -- they stretch long and powerfully to get the most out of each armstroke. Relax, reach and follow through each stroke as you swim.

Another way to add excitement to workouts is as simple as a new method of counting your laps.

For example, instead of lolling back and forth for 66 lengths -- a swimmer's mile in a 25 yard pool -- break the swim into 11-10-9-8-7-6-5-4-3-2-1 lengths. First swim 11 lengths, counting them backwards (11, 10, 9, etc.) Then rest for 15 to 30 seconds. Now swim 10 lengths, counting backwards. Rest for 15 to 30 seconds. Continue by swimming nine lengths, then eight, etc. By the time you've swum your last lap, you'll have completed 66 lengths. And instead of losing track and losing interest by counting from 1 to 66, the decreasing numbers will give you incentive as you tire.

Another form of "broken swim" is the pyramid. Pyramids are a method of training in which you increase and then decrease the number of lengths you swim at a time. For example: Let's say you want to swim 36 lengths, or 900 yards. Do a "six pyramid" by swimming one length, resting five to 10 seconds, followed by two lengths (or 50 yards in a standard 25-yard pool), rest, three lengths, rest, four lengths, rest, five lengths, rest, six lengths (or 150 yards), rest, and then work your way back down.

When doing a "six pyramid" (1-2-3-4-5-6-5-4-3-2-1), you may be tired when you hit six, but the decreasing numbers will give you a psychological edge to keep pushing harder. It's simply a more efficient way of counting laps.

Ladders are similar to pyramids, except that each "rung" equals several lengths, usually expressed in yards (100 yards is four lengths, for example). If you want to swim 64 lengths, or 1,600 yards, try swimming it as a ladder in the following way:

100, 200, 300, 400, 300, 200, 100, for a total of 1,600 yards, or 64 lengths. Swim four lengths and then rest 15-30 seconds, followed by eight lengths (rest), 12 lengths (rest), 16 lengths (rest), 12 lengths again (rest), eight lengths (rest), and finally four lengths. Congratulations! You've just used your pool time in a much more accurate and vital way than if you'd counted from 1 to 64.

Clocks and Equipment

Speedplay is another workout motivator. Try changing your pace every now and then to vary intensity. For example, if you're swimming 20 lengths, try surging, or going all-out, every fourth length.

If your pool has a large clock with a minute and second hand that is clearly visible, try establishing your own "personal bests" or private meets by testing yourself against the clock. Try swimming a prescribed distance a specified number of times on a constant time interval.

For example, to swim 500 yards (back and forth 10 times in a 25-yard pool), pick a suitable time and repeat each 50 yards within a specified time limit. Let's say you can swim 50 yards comfortably but slightly pushed in one minute. You would then use one minute as your interval time. When the second hand hits 60 on the pace clock, push off and swim to the opposite wall and back. How long did it take you? Fifty-five seconds? You then have five seconds to rest before the second hand hits the clock's 60, whereupon you should push off again and aim to get back to your starting place before it hits 60 again. Try to complete 10 such intervals, always leaving on the clock's 60.

Keep in mind that these times and distances are only hypothetical. If 10 lengths is all you can manage, that's fine. You can still apply the "different counting" principals. Swim 4-3-2-1, resting between each segment. If it takes you two minutes to swim 50 yards, give yourself an interval time of 2:15 and try five sets. You'll be surprised how quickly your swimming improves.

Even if you don't like the idea of using the clock or competing, whether with yourself or with the rest of the dolphins in your lane, you'll eventually need to inject variety and excitement into your aquatic bouts. The above methods are the time-tested ways to turn humdrum back-and-forth into real events. Other methods include adding some swim equipment into the mix:

*Kickboards keep your upper body afloat and allow you to practice your footwork. Try kicking for 10 minutes straight -- it's a lot tougher than it sounds. The board allows you to isolate your leg muscles and develop a better sense of balance and propulsion. Think of starting your kick from the abdomen and hips rather than your knees. Relax those ankles.

*Pull-buoys are two styrofoam cylinders held together by a strap that you may find poolside next to the kickboards. Hold them between your thighs to support your hips, and off you go. Your kick will be practically nonexistent, which allows you to concentrate on your arm strength and pulling technique.

Slow down and concentrate on the way you're stroking through the water -- pull-buoys often reveal a myriad of mistakes. Try mixing some kicking and pulling lengths or drills into your regular swimming for variety and more finely honed strength building.

*Fins can help you develop increased ankle flexibility, but don't become dependent on them.

*Tubes can be twisted around the feet to prevent kicking entirely, and work your arms.

*Paddles help you work on your stroke because they'll overload the shoulder muscles and fall off your hands if your stroke is incorrect. Use them judiciously under a coach's direction.

*Tether systems may be anything from a single rope around the swimmer's waist and a starting block to an elastic piece of surgical tubing to a complicated system of weights and pulleys. It's the best way for a good swimmer to get a workout in a small backyard pool, but be careful. They've been known to break and cause injuries. One backyard pool remedy might be simply to hold onto the side and kick, and then add some pull-buoy lengths for good measure.

Whether you opt for pyramids and intervals or kickboards and pull-buoys or some combination, the secret to making swimming a lifelong adventure is to stay challenged. Set goals for yourself, join a masters group box, Page 15 or take occasional breaks from your sport when needed to keep it fresh. Why not intersperse your pool workouts with running or train for a triathlon?

Water is a healing medium, and the health and confidence swimming imparts is like no other sport around. It's at once invigorating and tranquilizing. Take the plunge.