The dangers of over-hydrating during a race

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Have you ever suffered from nausea, swollen fingers and an uncomfortable stomach during a race? Then you may have experienced overhydration rather than dehydration. A combination of high water intake and low renal output (urinating) can cause abnormally low blood sodium levels, leading to a dangerous condition known as hyponatraemia. 

Sodium is an electrolyte that plays a key role in regulating many important functions in the body, like regulating the body’s fluid balance and supporting the central nervous system.

In an effort to be well-hydrated on race day, runners often drink too much water in the last few days leading up to the race, or they drink too much during and after the run, making themselves susceptible. It often occurs after running for four or more hours - the idea being the longer you’re out on the course, the more fluids you may be taking in.

Hyponatraemia can cause many health issues that range from mild to life-threatening. The brain is especially sensitive to changes in the sodium levels, which is why often the first symptom of hyponatraemia is confusion. Other symptoms include dizziness, headaches, fatigue, irritability, muscle weakness, cramping, nausea and vomiting. Runners may even become disoriented, unconscious, or experience seizures.

Oddly enough, the symptoms of hyponatraemia and heat illness are very similar and often can only be differentiated by a blood test. It's very important to distinguish between the two conditions because while symptoms are similar, the treatments are different. Get to the medical tent immediately if you experience any of these symptoms again.

Here are some tips for avoiding hyponatremia:

  1. Drink small amounts of fluids if you’re thirsty, but don't force yourself to drink.
  2. Add electrolytes to your pre-race fluid consumption, in capsule form and/or include some sports drink to your intake.
  3. Alternate taking water and sports drink during the race; water at one aid station and sports drink at the next one.
  4. When aid stations are frequent, like every mile, take fluid at every other station.
  5. Try salty snacks like pretzels or crackers for alternative run nutrition. 
  6. Take electrolytes during training runs and/or races. 
  7. Avoid taking any NSAIDS before or during the race if at all possible.
  8. Eat a good pre-race breakfast, one that you are familiar with like a bagel with peanut butter.
  9. Stop drinking if you hear or feel your stomach sloshing.
  10. If you don't feel well, get to the medical tent quickly.