The group makes special recommendations for athletes in the area of water, sodium and potassium.
The International Marathon Medical Director's Association also revised guidelines regarding hydration for athletes in May 2006. They recommend drinking a sports drink when exercising thirty minutes or more. They also state that during a marathon, it's best if runners listen to they body and drink when they feel they need to.
Hyponatremia, or water intoxication, was the result of this "drink, drink, drink" mantra, and now recommendations are going the other way, "Drink Less." For many exercisers water intoxication is a very real and very serious complication from drinking too much water. The numbers of triathlon and marathon participants who develop symptoms of water intoxication, continue to grow as more and more novice exercisers have entered these events.
So what is the right amount of fluid to drink? Well, that all depends, and in fact, it may not be that important to try to figure it out.
The longer and more intensely you exercise, the more important it is to replace lost fluids. And for an elite athlete, a loss of two percent of body weight in fluid has been linked to a drop in blood volume. This makes the heart work harder in order to move blood through the bloodstream. For elite athletes this decrease can result in a slight decrease in performance.
Dehydration in athletes may also lead to fatigue, poor performance, decreased coordination and muscle cramping. The American College Of Sports Medicine provides guidelines for athletes regarding proper hydration and fluid replacement.
If you feel that you need some sort of guideline to determine how much you should be drinking, use the following as a starting point.
Drink no more than 1 cup of water every twenty minutes. You can also weight yourself before and after you exercise to get a sense of how much fluid you typically lose. One pound is equivalent to approximately 24 ounces of fluid.
Sports drinks can be helpful to athletes who are exercising at a high intensity for 60-90 minutes or more. It's necessary to replace losses of sodium, potassium and other electrolytes during exercise. Keep in mind that under normal situations most exercisers are unlikely to deplete these minerals during regular training. If, however, you find yourself exercising in extreme conditions or for long times (an Ironman or ultramarathon) consider adding a sports drink with electrolytes.
Hyponatremia (low blood sodium concentration) may occur during longer events when athletes drink excessive amounts of plain water.
Lewis G. Maharam, MD.FACSM (chair),Tamara Hew DPM, Arthur Siegel MD, Marv Adner, MD, Bruce Adams, MD and Pedro Pujol, MD, FACSM. "IMMDA Revised Fluid Recommendations for Runners and Walkers." IMMDA. 6 May 2006.