WRITTEN BY RICHARD SEVEN PHOTOGRAPHED BY MIKE SIEGEL

	While experts say plain water is the best aid for keeping your body in top form, sports waters and other sports drinks can be helpful to people doing certain kinds of exercise.

Yet, how much is enough? Too much? Too little? Are you sating your need? Thirst alone can be unreliable.

The rule of thumb, which has come under recent challenge, suggests you should drink 48 to 64 ounces each day. Dr. Emily Cooper of Seattle Performance Medicine takes it a step further. You should drink half your weight in ounces every day. For example, if you weigh 160 pounds, you should drink 80 ounces. And, she says, you should add four more ounces of water for each eight ounces of caffeinated drinks you down. That's just walking-around hydration. Incorporating hydration into a workout is a bit more complicated, and usually overlooked.

For one thing, each of us has a different "sweat rate." The aerobically fit actually sweat more when they exercise because their bodies are working efficiently to cool down, like tuned-up engines. To find your sweat rate, Cooper suggests weighing yourself naked just before beginning an hour of moderate exercise. Don't drink anything during or after the workout. Don't shower; towel-dry perspiration before stepping on the scale again.

How much weight did you lose? One to two pounds is normal. For each pound of sweat you lose, you need to replenish with 16 ounces of water per hour while working out at a similar level.

"It's good to replenish fluids as you exercise," Cooper emphasizes. "Fluids help carry oxygen to the muscles and the heart. For regular exercisers, maintaining a constant supply of water in the body is essential to performance."

Some studies suggest that athletes typically replace only about 50 to 70 percent of the fluid they lose. Dehydration prevents the body from cooling itself, which can lead to muscle fatigue and loss of coordination. In extreme cases, it leads to heat exhaustion or heat stroke. Flooding your body, which is relatively rare, causes problems, too.

Cooper and her staff offer support at various distance races during the year and often see the effects of improper hydration. Some drink too little or too much water. Women tend to over-hydrate, she says, while men tend to drink too little. It gets tricky, though. Heat, exertion and a person's level of fitness all play roles.

She also suggests eating crackers or some other salty snack, such as pretzels, after a workout to replenish sodium, which in turn generates more thirst for the water you need to replenish and helps retain it. Although another contested issue, most experts note that thirst is not always the best indicator of how much fluid and sodium replacement is needed after prolonged exercise and heat exposure, especially among older exercisers.

So-called sports-water drinks have become a huge and growing industry. Cooper says they are a good choice, because besides water, they contain needed carbohydrates and salts. Some sports scientists say the real value of these water products is that they are flavored and induce the athlete to drink more.

Sports-drink makers have invested a lot of money in not only finding the proper flavor but devising catchy image-building names, but some experts say that casual athletes will do fine with plain, old water as long as they pay attention to nutrition.

And there is a difference between sports waters and sports drinks. Sports waters are probably good enough for people working out relatively lightly, and sport drinks, which carry greater concentrations of sodium, are better suited for those people exercising hard and long.

PJ Glassey, owner of the X Gym in downtown Seattle, says plain, pure water is tops.

"Mineral and sparkling water often contain too much sodium," he says. "Soft drinks are even worse. Although their main ingredient is water, less than 10 percent of it will be absorbed because of all the preservatives, dyes, flavoring agents, sugar, sodium and additives.

Here are some general hydration tips, courtesy of McKinley Health Center at the University of Illinois at Urbana-Champaign:

• Drink one to two glasses of water when you get up in the morning.

• Keep a water bottle with you throughout the day.

• Drink one to two cups of fluid 30 minutes before exercise.

• Drink ½ to 1 cup of fluid for each 15 minutes of exercise.

• Replenish lost fluids after workouts (2½ cups for every pound lost).

• Water is fine for lower-intensity exercise lasting 45 minutes or less. Sports drinks are a better option for higher-intensity exercise lasting 45 minutes or more.

Richard Seven is a Pacific Northwest magazine staff writer. Mike Siegel is a Seattle Times staff photographer.

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