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Health Options
Alan Titchenal |
Triathletes pique curiosity
of scientistsThe Kona Ironman World Triathlon Championship, the Superbowl of triathlons, took place Saturday. About 1,500 of the best triathletes from around the world spent a very long day in the Kona heat to complete a 2.4-mile swim, then ride a bicycle for 112 miles and, finally, run a 26.2-mile marathon. It is interesting to ask, "Why do they do this?" You might get 1,500 different answers.
But scientists are asking, "How do they do this?" Their research is beginning to paint a picture of the demands placed on triathletes. Although they might be considered extreme athletes, lessons we learn from them could well apply to those who are only moderately active.
Question: How many calories does a triathlete burn in an Ironman event?
Answer: The typical female triathlete expends 8,000 to 9,000 calories to swim, bike and run her way through the event. Due to a greater body weight, the average man expends 9,500 to 10,500 calories.
Q: How much weight is lost?
A: During a single day of an Ironman triathlon, athletes commonly lose 5 to 6 pounds. On average this includes about 13 ounces of body fat and 20 ounces of carbohydrate drawn from stores in the muscles and liver, for a total of about 2 pounds. The other 3 to 4 pounds is water loss.
Q: How much water is lost?
A: This varies tremendously. A typical rate of water loss in sweat is about one liter per hour while biking and running -- usually for about 12 hours. So that amounts to about three gallons total during the event.
Q: How much do Ironman triathletes eat and drink in the event?
A: Plenty, but not enough in calories to equal what they use up. Both males and females usually take in a little less than half of what they burn, typically 3,000 to 4,000 calories. Most of this comes from the carbohydrate in sports drinks and a variety of foods. So more than half the energy used to complete the triathlon is derived from the supply stored in their bodies.
Most drink enough fluids to replace all but about one to two liters of sweat loss. This amount of net water loss still allows them to stay normally hydrated.
Q: How much salt is lost?
A: The amount of salt in sweat varies from one person to another. A reasonable estimate is about 30 grams, or six teaspoons, lost. Obviously, a low-salt diet could backfire on an Ironman triathlete.
Q: Would nutritional supplements be helpful or harmful?
A: In 2002, 19 Ironman participants were given 800 IU of vitamin E for two months. Dr. David Nieman from Appalachian State University was surprised to find greater signs of oxidative stress and inflammation among these athletes than in 17 who took a placebo. Clearly, much remains to be learned about the benefits and risks of supplements.
See the Columnists section for some past articles.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, UH-Manoa. Dr. Dobbs also works with the University Health Services and prepares the nutritional analyses marked with an asterisk in this section.