Replacement of water losses incurred during exercise, or lost from the body through urination, etc. Rehydration is of particular importance to athletes performing repeated bouts of exercise, and to those performing in sports lasting more than 50 min. Without adequate rehydration athletes become dehydrated and their ability to perform is diminished. Water loss during and after exercise is reflected in a loss of body weight. Each 0.5 kg lost, should be replaced with about 500 ml of fluid. Rehydration is best achieved by replacing electrolytes (especially sodium ions), as well as water. Drinking plain water reduces the thirst stimulus and increases urinary output, both of which delay rehydration. Replacement is best accomplished with a cold drink (8–13 °C), slightly hypotonic, and low in sugar (sugars retard gastric emptying). The optimum sugar concentration depends on the individual, but 7% or less is commonly used. Water replacement should not exceed the maximum absorption rate (about 800 ml h−1). See also hyperhydration, thirst mechanism.
Subjects: Sports and Exercise Medicine.