Hyponatremia & Endurance Racing

This coming weekend is a favorite event here in San Diego.  Thousands of runners, joggers and walkers flood our streets for the Rock ‘n’ Roll Marathon and Half-Marathon, one of a series of Rock ‘n’ Roll events held across the country.

As a favorite destination spot, our event attracts many first time marathoners.  They’ve done the training and are excited for the race.  And if we get a sunny San Diego day – they’ll be drinking a lot of water along the course.

Keeping hydrated is really important during any endurance race, but some people really don’t like the taste of the sports drinks out there, choosing plain water instead.  Although there is nothing wrong with this in theory, in large amounts, water can be lethal.

Sound hard to believe? Your body actually needs a combination of water and sodium (think salt), like you find in sports drinks.  Sodium is an electrolyte that helps regulate the water level in and around your cells.  Ingesting too much water creates an imbalance between the levels of sodium & water which we call hyponatremia.

This can be a dangerous condition as the imbalance causes your cells to swell with excess fluid.  Most cells can adapt.  Brain cells, however, are confined by the unyielding skull.  The resulting swelling in the brain can cause a whole series of adverse conditions such as hallucinations, fatigue, convulsions, headaches and muscle spasms.

It’s for this reason that medical teams on the race course no longer immediately administer fluids to collapsed racers.  Instead, they usually wait a little while longer to conduct testing and try administering a sports drink that has sodium in it.

Our nutritionist, Sabrina, often recommends a sports drink, flavored or not, after 60-90 minutes of exercise.  Since most of us can’t finish a marathon (or even a half marathon) in that time frame, we suggest heeding her approach to hydration.