Dehydration is the most common performance-sapping mistake that athletes make, but it's also the most preventable. Here are some guidelines to help athletes stay well hydrated. Remember that everyone sweats differently and therefore needs to drink a different amount of fluid during exercise.

DO

Start exercise well hydrated

Drink 2-3 cups (475-700 ml) of fluid 2-3 hours before exercise to allow excess fluid to be lost as urine. About one-half hour before exercise, drink 5-10 oz (150-300 ml). There is no benefit to hyperhydration, so don't drink excessively.

Weigh yourself

The best way to determine if you'd had enough to drink during a workout is to check to see how much weight you've lost. Minimal weight loss means that you've done a good job staying hydrated. Remember that weight loss during an exercise session is water loss, not fat loss, and must be replaced.

Drink during exercise

Most athletes find it helpful to drink every 10 to 20 minutes during a workout. Heavy sweaters can benefit from drinking more often (e.g., every 10 minutes) and light sweaters should drink less often (every 20+ minutes).

Ingest sodium during exercise

The best time to begin replacing the sodium lost in sweat is during exercise. That's one reason why a good sports drink is better than plain water.

Follow your own plan

Everybody sweats differently, so everybody needs a drinking plan tailored to his or her individual needs.

Drink plenty during meals

If you weren't able to drink enough during practice to keep from losing weight, be sure to drink enough before the next practice. Mealtime is the best time to do that because of the ease of drinking and the sodium that comes along with food.

DON'T

Don't rely solely on water

Drinking only water keeps you from replacing the electrolytes lost in sweat and from ingesting    performance boosting carbohydrates that help you train longer and stronger. Excessive water drinking can lead to dangerous electrolyte disturbances.

Don't overdrink

Water is definitely a good thing, but you can get too much of a good thing. Drinking large amounts of fluid is not only unnecessary, but can be downright dangerous. Bloated stomach, puffy fingers and ankles, a bad headache, and confusion are warning signs of hyponatremia.

Don't gain weight during exercise

A sure sign of drinking too much is weight gain during exercise. If you weigh more after practice than you did before, that means that you drank more than you needed. Be sure to cut back the next time so that you don't gain weight.

Don't restrict salt in your diet

Ample salt (sodium chloride) in the diet is essential to replace the salt lost in sweat. Because athletes sweat a lot, their need for salt is much greater than for non-athletes.

Don't use dehydration to lose weight

Restricting fluid intake during exercise impairs performance and increases the risk of heat-related problems. Dehydration should be kept to a minimum by following a wise fluid-replacement plan.

Don't delay drinking during exercise

Stick to a drinking schedule so that you avoid dehydration early in exercise. Once dehydrated, it's next to impossible to catch up to what your body needs because dehydration actually slows the speed at which fluid exits the stomach.