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Runners’ Big Mistake: Overloading on Fluids

Runners’ Big Mistake
Runners’ Big Mistake

Many recreational runners hold mistaken—and potentially dangerous—beliefs about hydration. Nearly half consume excessive amounts of water or sports drinks during races, putting themselves at risk for potentially serious health problems, reports a recent study from Loyola University published in British Journal of Sports Medicine. The researchers also found that another common misconception is that runners need to ingest extra salt.

Here’s the irony: the main reason why runners’ sodium levels dip during races is drinking too much water or sports drinks. And fluid overload can add up to more than a temporary threat to the body’s sodium levels: in some cases, it can bring on a potentially fatal exercise-associated condition, hyponatremia, sometimes called “water intoxication”. In recent years, 12 runners have died from this disorder and doctors suspect that another eight deaths among runners may have been due to the same problem. Here’s what all runners should know about what to drink and when to drink it:


How many runners are misinformed about fluid consumption during races? Expert guidelines advise runners to only drink when thirsty. But 36.5 percent of the runners the Loyola researchers surveyed reported drinking according to a preset schedule or to maintain a certain body weight, and nearly nine percent said they aim to drink as much as possible during races. Nearly a third of those surveyed erroneously believed that they need to take in extra salt while running, and more than 57 percent said they down sports drinks because they believe that the electrolytes in these beverages prevent sodium levels from falling. Actually, the main cause of low sodium in runners is drinking too much water or sports drinks, the researchers concluded.

What’s behind these mistaken beliefs? Misconceptions among runners about the need for liquids during races may stem from advertisements for sports drinks during the 1980s and 1990s, some of which recommended that runners drink as much as five cups per hour, the Loyola researchers said. Sports drink manufacturers have changed their tune, but the unscientific beliefs triggered by these ads persist, causing many runners to think they should drink as much as they can or drink according to a preset schedule, “We have been trained to believe that dehydration is a complication of endurance exercise,” said Loyola exercise physiologist Lara Dugas, PhD, a co-author of the study, in a statement. “But in fact, the normal physiological response to exercise is to lose a small amount of fluid.”


What are the symptoms of hyponatremia? Also known as water intoxication, this dangerous condition develops when excess fluids from drinking too much dilute the sodium content of the blood to abnormally low levels. Symptoms include nausea, vomiting, headache, confusion, loss of energy, muscle weakness, spasms or cramps, and in extreme cases seizures, unconsciousness and coma. Treatment depends on the severity of the case. For mild or moderate symptoms, runners may be advised to cut back on liquids temporarily or to take a diuretic to help increase sodium levels in the blood. In severe cases, an intravenous sodium solution may be recommended or doctors may prescribe medication to bring symptoms under control.

How much should runners drink during races? That depends on how thirsty you get. Guidelines from the International Marathon Medical Directors Association recommend that runners drink only when thirsty and cite scientific evidence showing that thirst protects athletes from the dangers of both drinking too much and dehydration by providing “feedback” from the body on its internal fluid balance. The guidelines state that runners or walkers planning to spend between four to six hours or more on a race course usually don’t need to drink more than one three-to-six ounce cup of water or sports drink per mile (three ounces for those weighing approximately 100 pounds and six ounces for those weighing approximately 200 pounds). Here’s a good rule of thumb: if you weigh more when you finish a race than you did before you began, you’re drinking too much. “Runners should expect to lose several pounds during runs,” Dugas says.

Are sports drinks better for runners than water? According to the International Marathon Medical Directors, sports drinks are your best bet when a race or a workout is longer than 30 minutes. These drinks contain carbohydrates and electrolytes that speed absorption of fluids and can give runners an energy boost. The medical directors discourage diluting sports drinks with water or alternating drinks between a sports beverage and water. That will only dilute the benefits sports drinks provide.


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