Hydration Strategies

No level of low body water is acceptable for achieving optimal athletic performance and endurance, so athletes must develop personal strategies for maintaining optimal body water while exercising. Imagine a full glass of water represents your body in a state of optimal hydration. When not exercising, it's like having a pinhole in the bottom of the glass. The water level will drop, but only at a very slow rate and at a pace that makes it easy for you to maintain an optimal hydration state. Because the water level drops so slowly, drinking an occasional glass of water or other fluid is an adequate means of maintaining hydration state. Now consider what happens when you exercise, which is equivalent to putting a pencil hole in the bottom of the glass: The rate of water loss is much faster. Within even a short period of time, the amount of water loss could be enough to affect exercise performance and endurance. Waiting to drink in this situation is not a reasonable option. If the frequency of drinking when not exercising is once every 2 hours, then the frequency of drinking during exercise should be once every 10 to 15 minutes. Water is lost so quickly during exercise that it becomes difficult, if not impossible, to replace the amount of water being lost and virtually impossible to increase body water while exercising. Waiting too long between drinks causes body water to decrease such that it cannot be adequately replaced. If you wait to drink you may be able to maintain the body's water level at its current state, but that state will be too low.

Without fluid intake, blood volume will quickly drop, sweat rates will drop, and body heat will rise quickly and dangerously, at the rate of approximately 1.8 degrees Fahrenheit (1 degree Celsius) every 5 to 7 minutes. Because it is so difficult to consume sufficient fluids during hard physical work, athletes should develop a fixed drinking schedule. With a loss of 1 liter of water per hour, athletes should find a way to drink 4 cups of water per hour. Athletes losing 2 liters of water per hour need to drink more than 8 cups of water per hour. Of course, it's difficult to know precisely how much water is being lost during activity, but a simple technique can help an athlete estimate how much is lost. One liter of water weighs approximately 2 pounds, and 1 pint of water weighs approximately 1 pound. By knowing these relationships, athletes can estimate how much fluid should be consumed during physical activity by doing the following:

Table 3.7 Effects of Dehydration on Aerobic Endurance Performance

• Hypohydration of >2% leads to decrements in performance.
• Cardiovascular function and temperature regulation are adversely affected.
• Maximal aerobic performance decreases 4 to 8%, with a 3% weight loss during exercise in neutral environments.
• Dehydration and GI distress are evident.
• Fluid and electrolyte balance in muscle cells is disturbed.
• Adverse effects of hyperthermia on mental processes contribute to central fatigue.

1. Write down what time it is just before the exercise session.
2. Write down body weight in pounds. (Preferably, this should be nude weight.)
3. Do the normal exercise, and monitor how much fluid is consumed during the exercise period.
4. Immediately after exercise, take off the sweaty clothing and towel dry. Once dry, write down body weight in pounds. (Again, this should be nude weight.)
5. Write down the current time.
6. Calculate the amount of fluid lost by subtracting ending weight from beginning weight.
7. Calculate exercise time by subtracting ending time from beginning time.
8. The amount of extra fluid that should be consumed during the activity is equivalent to 1 pint (16 ounces) of additional fluid for each pound lost, provided in 10- to 20-minute increments.

Example: If John weighs 4 pounds less after a 2-hour football practice, he should consume an additional 4 pints (8 cups) of fluid during that practice. He was already consuming 2 cups of fluid, so John's total fluid consumption should be 10 cups of fluid per 2-hour practice. In 2 hours there are 12 10-minute time increments, so John has 12 opportunities to consume 10 cups of fluid. Therefore, John should consume 6.5 ounces of fluid, or a bit more than 3/4 of a cup (10÷12 = .8), every 10 minutes or 13 ounces of fluid (about 1.5 cups) every 20 minutes.

Fluid Intake Before Exercise

Fluid Intake During Exercise

Fluid Intake After Exercise