WATER

Water is essential for athletes. At rest, athletes need at least two quarts of fluid daily. An adequate supply of water is necessary for control of body tempature during exercise, for energy production, and for elimination of waste products from metabolism. Dehydration - the loss of body water - impairs exercise performance and increases the risk of heat injury.

Consuming adequate fluid before, during, and after exercise is vital for safeguarding health and optimizing athletic performance. Athletes should drink 14 to 22 ounces of fluid two to three hours before exercise. During exercise, athletes should drink 6 to 12 ounces of fluid every 15 to 20 minutes. Fluid intake should closely match the fluid loss from sweating to avoid the detrimental effects of dehydration. After exercise, athletes should drink at least 16 to 24 ounces of fluid to replace every pound of body weight lost during exercise. Replacing lost fluids as quickly as possible after running will speed up your recovery.

Thirst is not an adequate guide to fluid replacement. Rule of thumb:

IF YOU ARE THIRSTY, YOU ARE ALREADY DEHYDRATED

Most athletes replace only 50 percent of their fluid loss during exercise. Athletes should replace fluids by drinking according to a time schedule rather than in response to thirst.

There are 2 excellent options-water and carbohydrate replacement drinks. The advantage of replacement drinks with approximately 4-6% carbohydrate is that they are absorbed as quickly as water, and also provide energy. Sports drinks containing carbohydrate and sodium are recommended during intense exercise lasting longer than an hour. The carbohydrate helps to delay fatigue, improve fluid absorption, and replace glycogen following exercise. The sodium helps to stimulate thirst, increase voluntary fluid intake, and enhance fluid retention.

THE DANGERS OF DEHYDRATION

Summer is here, along with the twin menaces of heat and humidity. Running in the heat can quickly lead to dehydration, which ranks up there with dobermans among runners' worst enemies. Dehydration hurts your performance, and slows your ability to recover for the next workout. Continuing to run when dehydrated can lead to heat stroke and death.

To better understand the dangers of dehydration, let's take a look at what happens in the body when you run on a warm day. First, your body automatically sends more blood to the skin for evaporative cooling, leaving less oxygen-rich blood going to your leg muscles. Second, the warmer it is, the more you sweat, and the more your blood volume decreases. Less blood returns to your heart, so it pumps less blood per contraction. Your heart rate must increase, therefore, to pump the same amount of blood. The result is that you cannot maintain as fast a pace on a warm day.

Worst of all, dehydration tends to catch you unawares. If you replace a little less fluid than you lose each day, after a few days you will run poorly but may not know why. Exercise physiologist and marathoner Larry Armstrong, Ph.D., induced dehydration equal to 2% of body weight in runners and observed a 6% decrease in speed over 5K or 10K. That's a 3% decline in performance for each 1% decrease in bodyweight due to dehydration.

It is not unusual to lose 3-4 pounds of water per hour when running on a warm day. At this rate, after 2 hours a 150 pound runner would lose 6-8 pounds, representing a 4-5% loss in bodyweight and a 10-15% decrement in performance. That's about an extra 1 minute per mile. Losing more than 4-5% of your bodyweight, however, could do even more serious damage to your body.