Run Faster... Stay Hydrated!
by Charles Garfinkle, BS, MPT
Sweating is your body's most effective way of cooling itself. When sweat evaporates from your skin, body heat is reduced. While sweating is important, not replacing fluids lost through sweat can lead to poor training, racing, dehydration and heat illness. That's why fluid replacement before, during andafter workouts and competition is crucial. During exercise, the heat produced by working muscles exceeds the heat released by the body, raising body temperature. The rise in body temperature causes an increase in sweating and blood flow to the skin. As a result heat is removed by the evaporation of sweat from the skin, radiated from the body to the cooler surroundings, and is lost by convection to moving air allowing you to cool.
Dehydration
Dehydration can be defined as "Loss of water content and essential body salts (electrolytes)". These are needed for normal body functioning, especially for training and racing. Dehydration is the lack of adequate fluids to carry on normal body functions. Vital organs like the kidneys, brain, and heart can¼t function without a certain minimum of water and salt. Dehydration is one of the most common heat diseases. Very few of us go through life without being dehydrated at some time or another. At times dehydration might be dismissed as a minor "irritation", but it is indeed something that deserves our full attention and warrants timely treatment. Warning signs of dehydration are dizziness or lightheadedness, muscle cramps, nausea, headache, dark urine, sudden fatigue, and dry mouth and throat.
You should drink fluids whenever you start to get thirsty during exercise. True or false? In a recent Consumer Reports survey, nearly 3/4 of the respondents answered wrong. The correct answer is false: You should drink fluids before you get thirsty. By the time you feel thirsty, you're already dehydrated, says Robert Murray, PhD, director of the Gatorade Exercise Physiology Lab in Barrington, IL. And when temperatures rise, so does your risk of dehydration. Here's how to prevent it:
- A. 2 hours before exercise: Drink at least 16 oz.
- B. 1 hour before: Drink at least 8 oz.
- C. During long endurance exercise (i.e., marathon training): Drink at least 4 to 8 oz every 15 to 20 minutes.
- D. After exercise: Drink at least 16 oz.
What to drink? Water, sports drinks, and juices are fine. Skip carbonated or caffeinated beverages; and if you're watching your weight, remember that water is calorie-free.
Research confirms that performance is impaired when an athlete is dehydrated. In long endurance exercises, such as a marathon, a progressive dehydration seems almost inevitable, says Ronald J. Maughan, Ph.D., professor of human physiology at the University of Aberdeen in Scotland. Dehydration occurs when the athlete fails to drink enough fluid to replace the sweat (water) lost during exercise. The resulting decrease in performance is accentuated if the athlete begins training or competing the next day in a state of dehydration, says Maughan. "Rehydration after exercise involves not only replacement of fluids lost in sweat, but also replenishment of electrolytes, primarily sodium." For optimal rehydration, you should drink a carbohydrate-electrolyte drink as soon as possible after training or competing, says Maughan. The carbohydrates and sodium in these drinks provide flavoring that helps to stimulate consumption. The sodium also aids in the retention of the consumed fluids. The result is better hydration, which has performance implications for your next training bout or competition. "Working on an effective recovery strategy," Maughan says, allows your training sessions to be completed with less fatigue and decreases the chance of injury.
Experts agree that sufficient fluid intake during long endurance exercise is preferable to drinking only before training or competition. However, total replacement of sweat lost during exercise is rare among athletes, who typically replenish less than 50% of their sweat during exercise. To help maintain normal stores of body water, an athlete should prehydrate before exercise, says David Lamb, Ph.D., emeritus professor of exercise physiology at The Ohio State University. Prehydrating, says Lamb, will improve cardiovascular function and body temperature regulation when it's impossible to drink enough during exercise. "To avoid dehydration, you should consume water or sports drinks both before and during endurance exercise." To help ensure normal body water stores, drink at least 16 oz of fluid before sleeping the evening before exercise and another 16 oz first thing in the morning, says Lamb. To help "top off" fluid stores, drink another 16 to 32 oz. The type of fluid you consume before exercise is important. Make sure you drink fluids containing small amounts of sodium, such as sports drinks. The sodium in these drinks will cut down fluid losses in excess urination, and better maintain hydration. "Unaccustomed drinking of large amounts of fluid before practice or competition can cause gastrointestinal discomfort," Lamb says, "Practice your hydration regimens during training before trying them in competition."
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For more information, or with questions, please email: PaulR@PainRelief-PT.com