Adequate fluid intake before, during, and after exercise is necessary for health and optimal performance. Athletes should drink enough fluid to alleviate their fluid losses. One way to estimate fluid losses are to compare pre and post ride body weights.
Endurance athletes, especially those who train in hot and humid weather conditions, constantly risk dehydration. The risk becomes greater the longer an athlete is working, and when athletes train or compete more than once a day. Dehydration decreases exercise performance it most situations.
Fluid Loss During Exercise
Most fluid loss during exercise is from sweating. Fluid losses per hour range from one- half liter to two or more liters of fluid (16 oz to 64+ oz) depending upon heat, exercise intensity, and individual physiology. It is reasonable to estimate that the body loses one liter of fluid per hour of cycling in temperate (70o F) conditions.
Example: If the body loses about one liter (32 oz, 1 quart) of fluids per hour of cycling, then after four hours of cycling about four liters (128 oz, 1 gallon) of fluids may be lost. Although in temperate conditions this may take four hours, in high heat (over 90oF) conditions, this can occur in less than a couple of hours.
How Much do Athletes Need to Drink?
Before: Drink 400 mL to 600 mL (14 oz to 22 oz) of fluid two to three hours before exercise.
During: Drink 150 mL to 350 mL (6 oz to 12 oz) of fluid every 15 to 20 minutes depending on duration, intensity, tolerance, and temperature. A six percent carbohydrate solution with approximately 300 mg of sodium per 16-ounces helps refuel and replace lost sodium (see the next page).
After: Drink at least 500 mL (16 oz) of fluid for every pound of body weight lost during exercise. If fluid losses are high, adding salt to fluids and foods will help with rehydration.
Bottom Line
Athletes often do not consume enough fluids during exercise to balance fluid losses. Health and performance may suffer. Drink adequate fluids to replace sweat losses during exercise.