Fast Facts: Balancing Fluid & Electrolyte Intake During Endurance Exercise to Avoid Hyponatremia

Hyponatremia occurs when drinking too much water and taking in too little sodium before, during, and sometimes after training and racing. Hyponatremia is also more likely to happen during longer events such as the marathon as opposed to shorter events like a 5k.

Moderate Hyponatremia Can Cause:

  • Bloating
  • Malaise
  • Headache
  • Nausea
  • Vomiting
  • Fatigue
  • Confusion
  • Persistent & involuntary leg movements

Severe Hyponatremia Can Cause:

  • Altered mental status
  • Coma
  • Seizures
  • Death

To Avoid Hyponatremia the American College of Sports Medicine Recommends:

  • Neither underhydrate or overhydrate, as both had significant consequences.  Shoot to drink 16-20 ounces of an electrolyte-beverage every hour when endurance exercise goes over 2 hours.
  • Determine your sweat rate by measuring the amount of weight lost after training. Add to that the volume of fluid consumed during exercise. Finally subtract that number from the volume of urine excreted, if any.
  • Drink to match fluid loss and on a schedule. Fluid should be consumed over a set period of time, rather than rapidly in a "catch up" fashion.  If you are not sweating much and are not thirsty, fluid replacement should be modest.
  • Consume salty foods and beverages. This will promote fluid retention and stimulate thirst. Those performing long-duration endurance exercise should consume snacks and fluids containing sodium to help prevent hyponatremia.

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