Q: What do you think of performance-enhancing and endurance-enhancing natural drinks?
_ David Fulcher, 40, St. Petersburg
A: Performance-enhancing drinks can be safe, effective and may reduce cramping and injury. During exercise, the body undergoes many physiologic changes.
Think of the body as a car engine. Heat is produced from a running engine just as heat is produced from an exercising body. A car has a radiator which cools the engine and allows the car to run better, faster and longer. Similarly, the body has a radiator mechanism. The body produces sweat, which cools the core temperature. The ideal performance solution must restore the water and electrolytes that the body has lost, and easily be absorbed.
During intense exercise, an athlete can lose 2 to 3 liters per hour, which is 5 to 7 percent of the total body water. In addition to water, sweat contains electrolytes, including sodium, chloride and potassium. However, a replacement fluid is of little value if it cannot be easily absorbed.
When the body is exercising, most of the blood is pumped to the muscles to sustain the activity. Consequently, very little blood flows to the digestive system. Therefore, the absorption rate of fluids is less during exercise than rest. Fluids that contain carbohydrates are absorbed more easily by the body. Also, cold fluids increase the rate of digestion and help bring down the core temperature.
Time of the fluid replenishment is just as important as the fluid. Two to 3 liters of fluid may be lost before feeling thirsty. In a long race or an intense workout, it is difficult to replenish the fluids that have been lost. This is commonly referred to as "hitting the wall."
To enhance performance and endurance, fluids should be consumed prior to a workout. For best results, fluids should contain electrolytes and 2 to 6 percent carbohydrates.
Dr. Koco Eaton is a St. Petersburg orthopedic surgeon, a former basketball player at Columbia University and a graduate of the John Hopkins medical school. You may call in your fitness-related question on our Hey, Doc phone line (893-8301) or by mailing your question to Hey, Doc, c/o St. Petersburg Times Sports, 490 1st Avenue S., St. Petersburg, 33701.