Watch out, Gatorade. There's a new genre of sports drinks that may someday give you competition. Marketers know that when performance is an obsession and when the difference between winning and losing is small, athletes will look for any edge, no matter what the cost.

While these latest drinks may have a valid purpose, they won't turn you into Walter Payton. And while some trainers believe that plain, inexpensive water is the best replenishment for an athlete, the new drinks are probably better for you than all the beers you may be downing while watching the Super Bowl today.

Not meant to replace food, the new drinks are being touted for their ability to slow down muscle glycogen depletion and extend endurance. Unlike products such as Gatorade, which are primarily made from simple sugars and electrolytes (sodium and potassium), the new drinks are made from glucose polymers -- small chains of glucose molecules that fall somewhere between a simple glucose unit and a complex starch.

Sort of a fluid version of potatoes, the drinks are a quick fix for carbo-loaders who don't have the time during intensive training -- or the capacity -- for pasta pig-outs.

Sold primarily in powdered form to which water is added, some of these products are already being used by professional sports teams, college and high school athletic departments and in fitness clubs. The Washington Capitals and Georgetown, George Mason and George Washington universities are among the Washington-area teams using Exceed, a product made by Ross Laboratories, a subsidiary of Abbott, the huge pharmaceutical company.

Coca-Cola is test-marketing a product called Max via sporting goods stores and health food sections of supermarkets in Houston and Denver. Vitex, a California company, sells two products -- Bodyfuel 450 to cycling teams and bike stores and Bodyfuel 100 to health clubs.

While these products are still limited and specialized in distribution, their manufacturers someday hope to hit the sports-enthusiast market, cashing in on a fitness craze that could reap hefty financial rewards.

Although the value of any supplementary products is controversial -- with one side claiming uselessness at the expense of the buyer, the other claiming usefulness, whether psychological or physical -- there is at least one area in which sports experts agree: For athletes, there is nothing more important for the body than replacing water.

According to Ellen Coleman, a registered dietitian, sports physiologist and program director of the Riverside Cardiac Fitness Center in Riverside, Calif., athletes need a constant supply of fluid to maintain a constant sweating rate. In a complex chain reaction, when the body becomes dehydrated, body temperature starts climbing, heart rate increases and exercise becomes more difficult, Coleman said.

The key, said David Costill, director of the Human Performance Lab at Ball State University, is to get people to drink more than their demand for thirst dictates; most people will satisfy their thirst long before they are normally hydrated. People are obviously more inclined to drink something that tastes good; thus the popularity of flavored drinks as a substitute for water.

But what is also important when it comes to fluids is the rate at which the fluids empty from the stomach and supply nourishment to the bloodstream, Coleman said. Simple sugars slow the rate of stomach emptying.

What the new drinks promise is fluid replacement with rapid stomach-emptying time, plus the advantage of supplying more carbohydrates for the amount of fluid than simple sugars. According to Keith Wheeler, manager of research and education for sports nutrition at Ross Laboratories, carbohydrates are found in the body in the form of glucose (stored in the blood) and glycogen (stored in the liver and muscles).

During short term, anaerobic exercise, the body does not depend on glycogen stores. But during moderate, prolonged exercise such as cycling, basketball, soccer or distance running and especially during high-intensity exercise such as sprinting, glycogen is used as an energy source for the muscles. Fatigue occurs when these stores are used up, wrote Wheeler in NSCA (National Strength and Conditioning Association) Journal.

Aside from saving these stores via endurance training, which conditions the body to use fat as an alternate energy source, another way to delay muscle fatigue is by increasing the amount of glycogen available to the muscle, according to Wheeler. Thus, the popularity of carbohydrate loading -- consuming high amounts of carbohydrate-containing food to increase muscle glycogen before an endurance event.

But some athletes see limitations to carbo-loading. Coleman, who said that she advocates a balanced diet before supplementing with glucose polymers, believes that athletes often get full before they have eaten enough carbohydrates. For instance, if a male marathon runner must eat 5,000 calories for his fill of carbohydrates, he may get full after 3,500, Coleman said.

In addition, Wheeler said that carbohydrates from food take longer to reach the bloodstream than those from fluids. Ninety percent of a pint of Exceed is emptied through the stomach in 30 minutes, he said. If an athlete were to ingest an equal amount of carbohydrates from potatoes, it would take three or four hours to digest and get into the bloodstream, Wheeler said.

Dan Riley, strength trainer for the Redskins, who has not yet seen the glucose polymer products, is skeptical about any supplementation. The questions one should ask, said Riley, are, "Is this essential?" and "Will it enhance performance?"

The manufacturers say yes, at least as far as the latter question goes. Tests on stationary bicycles performed in lab settings by Ross Labs have shown that supplementing with a glucose polymer enabled cyclists to work 33 minutes longer before they reached the point of fatigue than non-supplemented individuals. And studies performed with the U.S. national bicycling team showed that on a bike course, riders who received Exceed instead of water finished 2 1/2 minutes faster. (In the blind test, the riders served as their own control group, doing the course twice, once with water and once with Exceed.) Wheeler said Ross Labs has also performed tests, inserting tubes down the stomachs of athletes, that showed that Exceed empties through the stomach as fast as water.

But Michelle Hamilton, product manager for Coca-Cola's Max, said that the company's research doesn't back up any claim that any carbohydrate drink empties through the stomach as fast as water. In addition, Hamilton said, Coca-Cola is not making any claims about specific percentages of improved endurance. There are too many variables among athletes and in exercising conditions, Hamilton said, such as how the athlete slept or the day's temperature. What the company does say is that Max can improve performance by rehydrating you correctly and rebuilding your energy stores quickly, Hamilton said.

While Riley cautioned against relying on testimony from successful athletes and emphasized the psychological power of many supplements, area sports teams and departments using Exceed seem pleased with the results.

Rod Langway, captain of the Capitals, drinks Exceed every day at practice, as well as before games, during intermission and after games. On the day of a game, he will typically eat an eight-ounce steak and spaghetti before he goes to sleep in the afternoon, he said. And when he gets up, he'll usually have an english muffin, peanut butter and three cups of coffee. (Some studies have shown that caffeine stimulates fat utilization and spares muscle glycogen. The school is still out on whether it enhances endurance capability.) When he gets to the arena, he'll down another two to three cups of coffee and maybe a banana and an orange before the game that night.

Frank Novakoski, athletic trainer at George Mason University, said that while he's not "a big believer in these drinks," Rob Muzzio, two-time NCAA decathlon champion, drinks a couple of quarts of Exceed prior to events, as well as during the 45-minute intervals between them. Although Novakoski said it is difficult to measure just how effective the product is, he says that Muzzio feels good the second day of the decathlon, one of the most grueling athletic events.

Doug Huffman, head trainer at Georgetown University, said that all the teams at that university use Exceed. And although Huffman believes that water is just as effective, he said that the key is fluid replacement, and that players can more easily consume large amounts of liquids that have more taste than water.

Aside from the glucose polymer drinks, there are a host of other sports drinks cropping up on the shelves of health food and sporting goods stores with names and packaging that look like something out of a Superman comic book. The idea of marketing sports drinks is nothing new; the well-known milk-based nutritional supplement Nutrament was being passed around locker rooms 25 years ago.

And, in fact, it still is. The New England Patriots had 60 cases of Nutrament delivered to their hotel in New Orleans. But in the end, all the wonder drinks don't mean anything when it comes to winning unless there's a good foundation. Said Bill Jarvis of the National Council Against Health Fraud, "It's training and natural abilities that make the difference."