In the know about H2O.

You're panting after practicing 32 fouettes at least 32 times. You reflexively reach for your water bottle, but wait--how much should you drink and when should you drink it? And did you know that too much fluid is actually as harmful as too little? On one hand, lack of adequate hydration makes you tired, irritable, and unable to properly digest--all factors that negatively affect performance. On the other, too much water can produce virtually the same symptoms. Water intake is a balancing act, and these tips will help you find the right balance.

Julie O'Connell, a physical therapist and consultant for the Joffrey Ballet and Hubbard Street Dance Chicago, says the amount of water a dancer drinks needs to be calibrated individually. "The hard part about giving a standard number is that a dancer's need is based on their metabolic rate," she says. "What and how much you drink depend on the intensity of your workout, your body weight, and your sweat rate."

Dancers are elite athletes who need water before and during exercising. When you have a mid-rehearsal break, you should have a bottle at the ready. "As quickly as we sweat, we need to replenish the fluid balance to prevent our bodies from going into dehydration" says O'Connell. One trick she recommends is drinking room temperature water, which is easier for the body to absorb than cold water.

But there also can be a tendency toward drinking too much. Dr. Arthur Siegel, assistant clinical professor of medicine at Harvard Medical School, began studying "water intoxication" in relation to runners, but says the warning signs apply to dancers, too. The syndrome occurs when athletes drink too much, causing an imbalance of salt and water in the body. A dancer who is overhydrated runs the risk of experiencing a drop in the blood's sodium level, which can lead to headaches, nausea, vomiting, weakness, and dizziness, and in some eases seizures and collapse--almost the same symptoms as dehydration.

Siegel feels some dancers may "tank up" on water to suppress their appetites. But that extra fluid can lead to temporary weight gain. "Dancers should know that sweat loss is proportional to intensity of exercise, and they can replace that loss with water." Replacing in excess of what you sweat can create problems. "If there is a decrease in urine production, or they gain weight or experience muscle injury," he says, "they need to drink less."

How you replace the sweat matters, too. "Plain water is better than nothing, but sports drinks are probably best," says Dr. Richard Gibbs, supervising physician for the San Francisco Ballet. Gibbs notes that if you're sweating a lot, water can make you lose your desire to drink, while sports drinks have a small amount of glucose and electrolytes that allow fast, proper absorption, and give the body a signal of persisting thirst if it needs more fluid.

Gibbs recommends drinking Gatorade for intense, high energy periods of rehearsal or performance. "It's right on the money with the electrolyte and glucose content," he notes. Dancers used to have to dilute it because the percentage of glucose was too high, but Gibbs says it's been reformulated with less glucose to a more drinkable blend.

If you want the benefits of sports drinks but prefer something natural, try coconut water. Full of unprocessed sugars, salts, and vitamins, it helps ward off fatigue, and contains more potassium than most sports and energy drinks. Gibbs does not recommend drinking most fruit juices, since they are too concentrated to quickly replenish lost minerals and fluids. "If you have to use juice, add water," he says. He also warns against trying to hydrate with sodas, since many contain caffeine, a diuretic, not to mention sugar and chemicals.

According to Gibbs, colorless or pale urine is a sign you've had enough fluids. He believes that for every pound a dancer loses during a workout or performance, they should drink two to three cups of fluid for replacement. He also says that if you sweat a lot, a cup of liquid every half hour is the generally accepted measure.

In the end, everyone has a different metabolism. What another dancer does may not work for your physique. Speak with a nutritionist to explore how much and what you should drink for your physiology, and keep a close eye on whether you're drinking too little--or too much.

Nancy Alfaro is a New York-based former dancer who writes frequently on dance.