Fluid Replacement in Athletes: How Much Is Too Much?

From the WebMD Archives

Dec. 17, 1999 (Minneapolis) -- During the last decade, researchers have learned a lot about fluid replacement in athletes and the importance of drinking liquids -- before, during, and after strenuous activities. Yet more recently, scientists have increasingly focused on what happens when too much fluid is ingested. Recent reports of several athletes who died after over-hydration have brought the issue into the spotlight.

The life-threatening condition known as hyponatremia occurs when excess fluids -- ingested orally or intravenously -- cause depletion of sodium in the body. With the increasing popularity of ultradistance triathlons and Iron Man events in the 1990s, the incidence of hyponatremia has risen, and the condition is now under close scrutiny by sports medicine specialists and scientists around the world.

In a 1999 study, researchers from Winn Army Community Hospital in Fort Stewart, Ga., reported the first known death of an Army basic trainee as a result of drinking too much water. When physicians misinterpreted his symptoms as being dehydration and heat injury, they continued to provide fluids intravenously -- so much so, that fluid levels overloaded the cells, tissues, and cavities of his brain and lungs.

Researcher Timothy Noakes, who is with the Bioenergetics of Exercise Research Unit at the University of Cape Town in South Africa, questions the use of intravenous fluid therapy in sports. "Must a collapsed marathon runner or army recruit or football player with muscle cramps die from hyponatremia before we finally question our ignorance?" he writes in an editorial in the October issue of British Journal of Sports Medicine.

Sports medicine specialist Douglas Stoddard, MD, of the Toronto Sports and Exercise Medicine Institute, tells WebMD that the key is not that athletes are over- or under-hydrated, but that many are under-replenished with sodium and potassium. He suggests that athletes eat foods that are high in potassium, such as bananas. Also, he says that it is important to "rehydrate with a fluid that contains enough sodium and potassium to balance the amounts lost in sweat, such as the newer sports drinks."

And not all athletes are created equal when it comes to fluid loss and sweat concentrations, Stoddard adds. "Depending on the volume and the concentration of sodium and potassium in their sweat, the person can run into problems that range from nausea, gastrointestinal discomfort, and muscle cramping to a drop in blood pressure, dizziness, coma, or death," he says.


With an eye on prevention, the American College of Sports Medicine (ACSM) says that adequate fluid replacement helps maintain hydration and, therefore, promotes the health, safety, and optimal physical performance of individuals participating in regular physical activity. The ACSM's general recommendations detail the amount and composition of fluid that should be ingested in preparation for, during, and after exercise or athletic competition.

A 1998 study published in the British Journal Sports Medicine concludes that "athletes should take their fluids orally, not intravenously -- if, that is, they are truly dehydrated and in need of rehydration."

Stoddard believes one of the best ways for athletes to get replenished is with one of the newer sports drinks that are formulated with higher electrolytes than the drinks developed back in the 1970s. "There's a new generation of drinks coming out soon," he says. As eastern medical director for the Iron Man Canada and medical director for the Subaru Triathlon Series, Stoddard is preparing to launch one of the new sports drinks.

Vital Information:

  • Hyponatremia occurs when the body becomes over-hydrated, causing a depletion of sodium in the body.
  • The incidence of hyponatremia has risen with the advent of ultradistance triathlons and Iron Man competitions.
  • Athletes can eat potassium-rich foods and drink sports drinks that contain enough sodium and potassium to replace what has been lost in sweat.
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