Ultrarunning: Hydration

December 20, 2011

This article is part of Endurance Planet’s ultrarunning article series. If you have questions, comments or feedback about “Hydration”, please leave it below in the comments section…

The need for sufficient and timely hydration during ultramarathons cannot be overstated. And runners need more than just the usual intake of fluids if they are to survive the grueling conditions of these challenging footraces.

Electrolyte balance

Maintaining a constant electrolyte supply in the body is one of hydration’s purposes. Electrolytes are a mixture of the minerals sodium, potassium, magnesium, chloride, hydrogen carbonate, and hydrogen phosphate. Healthy electrolyte levels ensure overall optimum performance of the body, especially of the brain, the heart, and the muscles.

Some minerals, most especially sodium, are displaced through sweating. When the subtle electrolyte balance is disturbed because of the latter’s depletion, muscle cramps and dehydration can occur. It is a given that runners will extensively sweat during the race, they then need to adequately replace the lost minerals through hydration to ensure that the delicate electrolyte balance is kept.


Ultrarunners are among the elite group of athletes who are subjected to some of the most extreme physical and environmental conditions out there. Overexertion from running very long distances and through extended periods are a given. And all these while being subjected to environmental factors such as ambient temperatures and humidity levels.

Needless to say, all these challenge the body’s capacity to thermo-regulate. And hydration is one of the most efficient methods of keeping the body’s temperature levels in check. This is particularly important if environmental conditions at the time of the race are characteristically hot and/or humid. Timely and adequate hydration minimizes heat-related conditions such as dehydration, heat exhaustion, and the life-threatening heatstroke.

Fuel supply

Some specially formulated sports drinks contain carbohydrates, compounds which when processed turn into calories that boost the body’s energy. Providing the body with calories is crucial especially if one is to run extremely long distances continuously. Inadequate calories not only mean lower performance, it could also bring about excessive production of cortisol, a hormone which is released by the body when it’s subjected to too much stress.

During this stage, the body will automatically turn to its own fuel storage to provide the much needed energy. And fuel will come from no other than the body’s own supply of fat and protein. So while presence of cortisol indeed helps in coping with stress, it also causes the body to consume itself, primarily the muscles where protein is stored.

Hydrating fully, ideally an hour prior to the run, is strongly advised. Some veteran ultrarunners take as much as 30 ounces of fluids every hour during particularly hot and humid conditions. And because sodium is lost through perspiration during sustained physical activities, then it’s equally crucial to ingest some salt prior to and during the race as well.

Remember that no one hydration plan works for every ultrarunner. Keeping track, not only of the total volume, but also of the particular levels of electrolytes in the fluids, will help one devise a hydration plan that’s appropriate for one’s own specific requirements.


Do you have questions about hydration, or what you’ve read so far? Do you have any ultrarunning pointers of your own to add? Please leave your feedback, comments and questions below, and we promise we’ll respond.

One Comment

  • Bill Lockton says:

    This is the way we have all thought it worked, but now Dr. Tim Noakes is about to publish a book that says we've got it all wrong. Since I learned that on this site, I would have expected at least a mention of the contrary point of view. Ben interviewed him a few months ago. As I recall, Noakes said that electrolytes do not need replacing because we self regulate and stop the excretion of them, thereby eliminating going into any sort of electrolyte debt. Any comments on that? I'm reluctant to recommend that myself until I've tested it thoroughly because I understood it the way you do, but I'm up to 4 hour runs without using electrolytes, and so far, so good. Maybe it works. Anyhow, thanks for bringing it up, and any commentary on Noakes' position would be welcome.

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