Fluid Replacement Key to Enhanced Physical Activity

Drinking fluids before, during, and after exercise is key to improved health, safety, and physical performance for everyone involved in physical activity, from walkers and gardeners to competitive athletes. In a recently issued statement, the American College of Sports Medicine (ACSM) has concluded that inadequate fluid intake during exercise can be physically harmful and proper rehydration is vital to maintaining cardiovascular health and a safe body temperature.

According to its newest Position Stand, published in the January 1996 issue of ACSM's official journal, Medicine and Science in Sports and Exercise, individuals should eat a nutritionally balanced diet and drink adequate fluids during the 24 hour period before an event. Special attention should be paid to the meal immediately prior to exercise to promote proper hydration before exercise or competition. To avoid or delay the negative effects of dehydration, individuals benefit from fluid intake prior to physical activity. For example, drinking fluids one hour before exercise will help maintain body temperature and lower heart rate.

ACSM recommends individuals drink about 17 ounces (about 500 ml) of fluid approximately 2 hours before exercise to promote adequate hydration and allow time for the excretion of excess ingested water.

During exercise, individuals should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all water lost through sweating (body weight loss) or consume the maximum amount that can be tolerated. ACSM recommends that fluids be near 59-72 degrees F, be readily available, and in a container easy to use for minimal interruption of the exercise routine.

The report emphasizes that individuals typically drink insufficient amounts of fluid to offset sweat losses. To prevent dehydration and premature exhaustion, fluid consumption should equal a rate of two cups of fluid per pound of weight loss. For instance, a person who loses 3-4 pounds of body weight during running or cycling needs to drink 6-8 cups of fluid during exercise to offset the fluid loss.

The Position Stand also suggests the addition of proper amounts of carbohydrates (sugars) and/or electrolytes (primarily sodium) to a fluid replacement solution for exercise events of greater than one hour. Including carbohydrates in the fluid ingested during exercise helps delay fatigue normally associated with physical activity. Either water or sports drinks can be consumed for physical activity lasting less than one hour.

Carbohydrate requirements can be met by drinking roughly 15-32 ounces (about 2-4 cups) per hour of fluids with carbohydrate concentrations in the range of 4-8 percent during physical activity. With this guideline, both fluid and carbohydrate levels can be met simultaneously during prolonged exercise. If the inclusion of electrolytes in the fluid replacement solution enhances taste, then including it is justified because drinking can be maximized. Electrolytes in fluid replacement solutions also reduce the risk of hyponatremia (low sodium level) for those exercising longer than one hour.

In addition to enhancing flavor, adding sugar or other complex carbohydrates in fluid replacement solutions is effective in increasing carbohydrate oxidation, delaying fatigue and improving performance.

The American College of Sports Medicine, headquartered in Indianapolis, Indiana USA, has more than 16,000 members worldwide in almost 60 countries. ACSM's mission is to promote and integrate scientific research, education, and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health, and quality of life.

For more Information Contact:

American College of Sports Medicine
401 W. Michigan Street
Indianapolis IN 46202-3233 USA

Mailing address:
P.O. Box 1440
Indianapolis, IN 46206-1440 USA

Telephone: (317) 637-9200
FAX: (317) 634-7817
Website: http://www.acsm.org