Hyponatremia
Too Much Water can be Fatal in Endurance Athletes
This condition is “the most common serious cause of exercise-associated collapse” according to Dr. Robert Sallis (Sports Science Exchange, Volume 17, 2004). Hyponatremia can either be brought on by dehydration causing a low blood volume resulting in a low sodium content or by hyperhydration (drinking too much water) diluting the sodium content to extremely low levels.
The risk of acute rehydration-related hyponatremia (sodium levels below 135 mEq/L) in marathon runners is frequent (about 13%) as reported by Petzold, A., Keir, G., & Appleby, I. (Journal of Medical Case Reports, 2007).
The normal range for sodium in the blood is between 135 and 145 mEq/L. Hyponatremia can range from mild to severe depending on the sodium concentration in the blood (Sallis, R., 2004):
- Mild - 131-134 mEq/L
- Moderate - 126-130 mEq/L
- Severe - less than 126 mEq/L
Physiology of Hyponatremia
Endurance athletes are cautioned to stay hydrated before, during, and after races. Unfortunately, too much water can cause a lethal physiological reaction in the brain. Drinking too much water can dilute the blood. Water rushes into the cells, including the brain cells. As brain cells increase in size, pressure is increased within the brain because of the limited space between the brain and the skull.
According to Dr. Lewis G. Maharam, the medical director for the New York City Marathon (New York Times, October 20, 2005) doctors can misdiagnose hyponatremia as dehydration and mistakenly treat the patient with intravenous fluids. This can exacerbate the problem.
Story of Mark Robinson
Mark Robinson competed in the 2004 Boston Marathon at the age of 27. The race was on a hot day with temperatures expected in the 90s. Robinson prepared by drinking a gallon of water before the race and drinking several cups of water at each water station during the race.
He continued to drink water after the race even though he wasn’t feeling well and started vomiting. His condition deteriorated until he collapsed in his parent's home. He was transported via helicopter to the Boston Medical Center and was given intravenous fluids because the medical team thought he was dehydrated (New York Times, October 20, 2005).
His condition deteriorated. He lapsed into a coma for four days. His diagnosis was hyponatremia. He has since recovered, but stated that he would never run a marathon race again.
Signs and Symptoms of Hyponatremia
The public needs to be educated that too much water is as dangerous as too little water. Both can be fatal. Endurance athletes need to be aware of the signs and symptoms of hyponatremia (Anderson, M.K., Parr, G.P., & Hall, S.J., 2009):
- Headache
- Confusion
- Nausea
- Cramping
- Bloated Stomach
- Altered Consciousness
- Swelling in extremities (fingers and ankles)
- Seizures
The difficulty is differentiating hyponatremia from dehydration because many of the symptoms are similar. Dr. Robert Sallis recommends that one should assume hyponatremia “if rectal temperature, blood pressure, and heart rate are normal in the collapsed athlete who exhibits a diminished level of consciousness” (Sports Science Exchange, Volume 17, 2004).
Although this condition can be fatal, most athletes “recover spontaneously after 1-3 hours of rest and supportive care” (Dr. Robert Sallis, 2004).
Recommended Amount to Drink During Exercise
Healthy athletes should not be dying from drinking too much water. Although athletes are told to "drink, drink, drink", the hydration message needs to be balanced with caution.
Athletes need to be educated as to what to drink as well as how much to drink races. Experts differ on their opinions as to the value of sports drinks in reducing hyponatremia.
Although Dr. Robert Sallis is an advocate for sports drinks containing sodium, others disagree as to the effectiveness of sports drinks in preventing hyponatremia (Dr. Lewis Maraham, New York Times, October 20, 2005). Dr. Maraham recommends no more than eight ounces of fluid every 20 minutes regardless of the type of fluid.
What do you think about this article?
More in Health & Wellness
Latest Articles