Hydration-Too Much Versus Too Little (Lori Muhr)

Posted: March 17, 2011 in Uncategorized

Balancing fluid intake is very important in marathon training and on race day.  It is essential in maintaining good health and enhancing performance in any endurance event. Until around the last decade, people concentrated primarily on preventing dehydration.  However, drinking too much fluid can be very dangerous and lead to hyponatremia, a life-threatening condition in which the blood sodium levels drop to a seriously low- level causing a possible seizure, coma or death.  Immediate emergency care is necessary for hyponatremia victims. It’s important to educate yourself on the symptoms of dehydration and hyponatremia so you can be aware and know what treatment is necessary.

The BAA usually supplies complete information about Hyponatremia in your race packet- READ IT THOROUGHLY.  The following are guidelines published by the American Running Association http://www.americanrunning.org/ and the American Medical Athletic Association http://www.amaasportsmed.org/:

Dehydration and Heat Illness Signs:

Headache Fatigue
Dizziness Nausea
Muscle Cramps Weakness
Irritability Vomiting
Heat Flush Abnormal Chills

Hyponatremia Signs (Look for a combination of symptoms):

Rapid Weight Gain Bloated Stomach
Nausea Wheezy Breathing
Seizure Dizziness
Apathy Confusion
Severe Fatigue Swollen Hands/Feet
Throbbing Headache Cramping
Lack of Coordination  


Risk Factors for Hyponatremia Include:

 -Drinking  too much fluid without adequately replacing the sodium lost in sweat

 -Endurance athletes- exercising more than 4 hours

 -Athletes on a low sodium diet

 -Salty sweaters- often have an obvious white residue on face and skin

Hydration Plan

 -Drink to Stay Hydrated- Don’t Overdrink-  Overdrinking before, during or after a race increases the risk of hyponatremia dramatically. 

 – Determine Your Sweat Rate- The best way to prevent over-drinking is to determine your hourly sweat rate.  Simply weigh yourself, naked, before your run.  Run for an hour, and weigh yourself on your return, naked.  Every pound you lose is equal to 16 oz. of water.  If you take water in during the run, add that to the weight loss to determine how much water is safe to drink per hour.  For example, if you lose 2 pounds, that’s 32 oz. you can drink in an hour (so 8 oz. every 15 minutes).  If you drink 12 oz. of water in that hour, then you add the 32 oz. (for 2lbs. of weight loss) and 12 oz. for (water consumed) to equal 44 oz. total per hour (or 11 oz. every 15 minutes).  This method gives you the best estimate of how much water you can safely consume during your event.

 – Maintain a Salty Diet- to make certain you replace all of the salt lost during training during training. During a long race (e.g. more than 4 hours), eat salty snacks such as pretzels and saltine crackers, especially if you are a salty sweater.

 – Favor Sports Drinks like Gatorade over water during your event to help keep your body hydrated, fueled and salted.  However, sports drinks alone will NOT prevent  hyponatremia- any fluid, if consumed in excess, can cause a drop in blood sodium.

– Recognize Warning Signs of both heat illness and hyponatremia and learn to distinguish between them.

Writing your pre-race weight on the back of your bib number can be a helpful precaution if hyponatremia is suspected during or after the race.  An increase in weight is a sure sign of hypontremia.  Also, knowing your approximate sweat rate will give you confidence in your hydration plan during the race.  When in doubt, stop drinking and seek medical help fast.


  1. Cheryl Reed says:

    Hi Rick,

    This was very helpful! I have found, however, that the sugar in the sports drinks upsets my stomach during a race. If I bring salty snacks for refueling during the marathon, such a pretzels, can I just stick with water for my fluids?

  2. Cheryl Reed says:

    Sorry, Lori! Once again, I didn’t look closely. Thanks for this helpful information!

    • Hello Cheryl,

      Lori is accustomed to me ALWAYS receiving credit for her hard work :-)! You might want to consider Coconut water or Pedialyte during your upcoming runs. Otherwise, water is always a safe bet.


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