- Thirst is NOT a reliable indicator for fluid replacement. If you wait until you are thirsty, odds are you are TOO LATE.
- Heat is a by-product of energy.
- When water is added to an athlete's body, it takes 2-4 hours for all fluid to equilibrate.
- Dehydration affects circulation first and intramuscular water later.
- As dehydration approaches 3% by weight, performance drastically drops off.
- Decreased plasma volume (blood H2O) impairs the body's ability to transport oxygen, affecting work capacity (training and racing!)
- Sodium is the major electrolyte lost in sweating.
- Sodium helps maintain water in intracellular space without inhibiting thirst.
- Dilute carbohydrate solution (5-8%) has been shown to improve endurance performance.
- Glucose polymer and electrolyte (Gatorade) improves endurance more than water.
- Fructose (Coca-Cola / orange juice) does not stimulate as much fluid absorption as glucose.
- Dehydration causes a decrease in blood fluid volume, while training will increase blood volume.
- Acclimatization is best accomplished by progressively increasing the duration and intensity of training in the heat over a 2-week period.
- Heat acclimatization results in:
- Improved Heat Tolerance--the body sweats at a lower temperature.
- Increased Sweating and Evaporation Mechanisms--sweat produced is more dilute and mineral content is conserved.
- Improved Distribution of Sweat--amount of sweat is not necessarily less, but distribution is over the body.
- Lower Skin and Body Temperature--for a given level of work, thus decreasing the amount of blood needed for cooling.
- Training ramifications:
- Drink early and often through exercise in the heat.
- Drink well before the onset of exercise.
- Drink in the days leading up to prolonged exertion in the heat.
- Drink 12-20 ounces of fluid 10-20 minutes prior to competition.
- Running through a mister/shower will not prevent a rise in body temperature during exercise.
- Fluids ingested during exercise should contain 5-8% carbohydrate and small amounts of electrolytes (Gatorade-type replacement fluids).
- Consume 8 ounces of fluid every 15-20 minutes.
- To compete well in an environment, you must train in it.
- Eating should be slowed substantially 4 hours prior to competition.
- Milk slows down the thirst mechanism.
- Athletes lose more iron in hot climates.
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