Electrolytes, Hydration and Long Distance Running

With all due respect to this expert exercise physiologist's opinion, her advice on the importance of taking in electolytes during marathons and long runs is not accepted by everyone.

Currently there is no evidence to suggest that humans incur any meaningful sodium deficits during exercise, even when the humidity is high and the individual is sweating profusely. -The Science of Sport

Summarizing another article in The Science of Sport about electolytes during a 2 hour run:

1. If you don't drink at all, your blood sodium level doesn't fall, it RISES!

2. If you replace 50% of your sweat losses with plain water in the same run, your blood sodium concentration remains in the normal range.

3. If you replace 100% of your sweat losses with plain water (2 liters in 2 hours- 1 liter is approx. 1 quart), your sodium concentration falls dangerously low, leading to hyponatremia.

4. If you replace 50% of your sweat losses with Gatorade, the result is comparable to the water trial.

5. If you replace 100% of your sweat losses with Gatorade, again the result is not much different- a 4 hour marathoner will likely end up in the hospital with hyponatremia.

Interesting that Hall believes adding salt to his drink helps him retain more fluid in hot weather. I wonder why he thinks that's not as important on a cool day?

While you certainly need fluid replacement during a long hot run, be careful not to over drink. Practice by weighing yourself before and after, and note that while losing a few pounds is normal, any gain is not! As for Gatorade during a long run, the calories are what you need, not necessarily the electrolytes.

I love the Science of Sport blog!