Reader Question: How much water should I drink while exercising? Should I be using a sports drink?
Susan’s Answer: Whether you are an athlete in training or just starting a fitness program for the first time keeping your body hydrated is very important to the function of our body’s cells and our performance in our sport.
When you are thirsty your body is already dehydrated at the cellular level. It is important to drink water throughout the day to keep our hydration levels up. Dark yellow urine is one indication of dehydration whereas a light and clearer color shows a hydrated body.
- All athletes should consume 400 to 600 ml (about 1 ½ to 2 ½ cups) of fluid two to three hours before exercising. This amount of fluid will help ensure that the athlete is not dehydrated and will allow the athlete enough time to absorb the fluid and comfortably eliminate urine before training or competition begins.
- Athletes who exercise in the heat should consume an additional 250 to 500 ml (1 to 2 cups) within two hours of the onset of exercise.
- Athletes who train or perform more than one hour may choose a carbohydrate beverage (CHO) instead of just water. The concentration of the carbohydrate beverage should not be more than 8%, although some athletes can tolerate higher concentrations.
- Fifteen to 30 min. before exercise, 300 to 500 ml more of a CHO beverage is consumed.
- Consuming a sports beverage before prolonged activity gives the endurance athlete the advantage of being able to delay fatigue (through carbohydrate intake) and prevent dehydration.
Events lasting less then one hour:
- Athletes competing in events lasting less than one hour may not have any opportunity to ingest fluid during the event.
- If competition lasts less than 60 minutes, it is recommended that 180 to 240 ml (¾ to 1 cup) of cold water is consumed every 10 to 15 minutes to prevent dehydration.
- Cold water is an excellent choice because it leaves the stomach faster than room temperature water, is absorbed rapidly, and is well tolerated.
- If the athlete has consumed proper amounts of dietary carbohydrate, muscle and liver glycogen stores should be sufficient for optimal performance, and only water needs to be consumed during exercise.
Exercise more then one hour or high-intensity intermittent exercise for one to four hours:
- Athletes engaging in continuous exercise for more than one hour (such as marathon runners) or athletes performing high-intensity intermittent exercise for one to four hours (such as soccer or basketball players) are at risk for hypoglycaemia, dehydration, and fatigue, factors known to decrease performance. Since both carbohydrate and fluid are needed, as a practical matter many athletes consume carbohydrate beverages.
- These athletes should consume 150 to 300 ml (approx. 6 to 12 ounces) of a carbohydrate/electrolyte beverage every 15 to 20 minutes during exercise.
- Water in the beverage helps prevent dehydration, and the carbohydrate provides glucose to prevent glycogen depletion. Both dehydration and glycogen depletion hasten the onset of fatigue.
- The electrolyte sodium helps the body retain fluid and stimulates the drive to drink more fluid.
- Some loss of electrolytes occurs during exercise because sodium and chloride are lost in sweat.
- Eating and drinking properly after training or competition is important because carbohydrates, water, and electrolytes lost during exercise must be replaced.
- Immediately after exercise and for the next six to eight hours, rehydration is imperative so athletes do not begin the next training session or competition in a compromised state.
- After exercise, sodium is beneficial because its presence influences the body to retain fluid and helps to maintain the drive to drink.
- Sodium and water are found in sports beverages, but the amount of sodium is low. In general after exercise, athletes could also lightly salt their food.
- Weigh yourself before exercise and then again after, for every pound lost drink a pint and a half (three cups) per pound lost. This is a minimum.
- Studies have shown that athletes do not voluntarily rehydrate after exercise. They need to have a plan to replenish fluid lost during exercise.
- Fluid consumption (and carbohydrate consumption) should continue for at least the next four to six hours.
Setting a plan for yourself to keep hydrated is a great way to ensure that your body is getting what it needs and that you are performing to your best ability. Good Luck in any upcoming events you are involved in and keep hydrated.
*As always before beginning any exercise program, please consult your physician.
About the Author: Susan Manning is a BCRPA TFL, ACE, ACSM, TWIST certified Advanced Health & Fitness Specialist in BC. She is Dr. Carolyn Anderson’s co-author of It’s Never Too Late To Be Fit, a comprehensive guide for older adult’s fitness.
Advanced Exercise Nutrition, Marie Dunford, Ph.D, R.D., Human Kinetics
Clinical Exercise Specialist Manual, American Council on Exercise, 2007