Optimal Racing Performance: Fluid Hydration

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It is difficult to replace water losses during exercise. The following principles will help prevent dehydration during endurance training and racing.

Troy M. Smurawa, M.D.
Member AMSSM

The Most Important Nutrient: Water
The most important nutrient to an endurance athlete is water. Without water an athlete will be in serious trouble trying to train and compete. Water is essential for many functions of the body. The body uses water for metabolic processes, to store energy and to dissipate heat. An athlete loses water at a rate of 1 – 3 liters per hour during exercise through sweating and breathing. Sweat rate is dependent upon acclimatization, conditioning, air temperature, humidity and wind.

Water Loss and Performance
Water loss leads to dehydration and increased body temperature. Weight loss with exercise is a good indication of the amount of water lost. One pound of weight loss equals 450 ml of water loss. Dehydration significantly effects performance. Every liter of water loss causes:

• An increase in heart rate by 8 beats per minute
• A decrease in cardiac output by 1 liter per minute
• An increase in core body temperature by 0.3 degrees Celsius
• A 2-3% loss of body water can lead to a 3-7% decrease in performance.

Principles of Water Replacement
It is difficult to replace water losses during exercise. The maximum amount a person can absorb during exercise is 750 – 1,000 ml per hour. Most athlete drink only about 300 – 500 ml per hour, which leads to a loss of 500 – 1,000 ml per hour. The following principles will help prevent dehydration during endurance training and racing:

1. Pre-hydrate to increase water stores; drink 4 – 5 sixteen-ounce bottles of water or fluid replacement daily.
2. Drink up to 32 ounces of water or fluid replacement one to two hours before competition or training. Drink an additional 16 ounces of fluids immediately before your race or workout.
3. During a race or workout lasting over an hour, replace fluids by drinking 4-6 ounces every 15 to 20 minutes. (24 ounces an hour)
4. In a triathlon, larger volumes of fluid are better tolerated during cycling. Consume larger volumes of fluids while cycling.
5. Cooler liquids are better absorbed during exercising.

6. Find a Sports Medicine Doc! Get in touch with hundreds of sports medicine doctors in your area through the AMSSM. Just go to the search page HERE on the www.amssm.org  website.

   An energy drink with 4-8% carbohydrate is better absorbed
7. Thirst is a poor indicator of dehydration. Your body is already 2-3% dehydrated when you begin to experience thirst. Drink regularly throughout the day and during exercise.
8. Weight loss is a good indicator of fluid losses. Weigh yourself before and after exercise. Replace every pound lost with 450 ml of fluids. Replace your fluids over 24 hours. Decrease your next training session if you are unable to replace lost fluids.
9. The amount and color of your urine is a good indication of your hydration status. Urine should be pale yellow, plentiful and frequent. Dark urine is a sign of dehydration.
10. Develop a plan for fluid replacement. Practice it in training to prepare you for racing. Find out the type of fluid replacement provided at the race and train with it. Trained athletes become better hydrated.

The information, prepared by a member of the American Medical Society for Sports Medicine, is not medical advice and should be used for informational purposes only. Please consult your own physician or health care provider about any opinions or recommendations with respect to your symptoms or medical condition.

 

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date: February 28, 2005