Warning by marathon race officials was dehydration. Athletes were told to constantly drink lots of water during long workouts after studies found a link bewteen dehydration and a rise in body temperature.
But now researchers are taking a second look at the risks of drinking too much fluid during exercise.
Hyponatremia, or water intoxication resulted in the deaths of two female runners in 2002, including one who ran in the Boston Marathon. In both cases, the women drank excessive amounts of fluids. What happens is the runner lose salt through their sweats, and drinking excessive liquids dilutes the sodium level in their bloddstream, resulting brain swell.
Symptoms of hyponatremia include nausea, vomiting, weakness and, in severe cases, seizures, coma and death.
So what should be the correct amount of water to dring? The advice is to drink when you are thirsty , because the body will instinctively know when it needs water.