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Electrolytes & Endurance Running

Updated: Oct 17, 2022

Electrolytes are a key component for many vital functions in the body: muscle function (including contraction, repair, and gastrointestinal muscle function), nervous system function, hydration status, and pH level maintenance. We lose electrolytes through our bodily fluids, so in the case of running, primarily through sweating and urination. Or, if you are having a particularly bad day, through vomiting and poop, too!

The electrolytes most abundantly lost during exercise through our sweat are sodium and chloride, and electrolytes lost in less concentration are magnesium, potassium, and calcium.

According to the American College of Sports Medicine (ACSM), on average, runners lose 0.4 to 1.8 liters of sweat per hour. This was measured both in cool (18C/65F) to moderately warm (28C/83F) temperatures. As you can see, this varies widely, which means each athlete’s sweat rate, and thus electrolyte loss, will be highly individualistic. Sweat rate varies by individual, and it also varies depending on many conditions: temperature, humidity, altitude, and current fitness status.

With sweat rates being so highly individual, you could imagine that electrolyte loss rates are equally as varied. And they are! You can get these both dialed in through a sweat test and a sweat concentration test, but I find those only necessary if you are really struggling to meet your hydration needs or are navigating a consistent issue, such as a GI problem.

We can meet our electrolyte needs in 3 ways during our running adventures and considerations about them:

  1. Through food consumed - This route can be the trickiest because it can be difficult to determine how much of each electrolyte you are consuming through food consumption. How much sodium is in 5 potato chips? I typically don’t recommend going this route, because it can be difficult to stay on top of electrolyte needs this way, especially if you start to have any food-related GI issues.

  2. Through an electrolyte drink mix such as Nuun, LMNT, Liquid IV, Osmo, etc. - Read the ingredients of the mix and make sure it is something that suits your needs, as some will be significantly higher or lower in sodium, and may not even include chloride, potassium, magnesium, and calcium. Next, check out if it includes any carbohydrates - glucose, or sugar, more specifically. If it doesn’t, you’ll want to make sure you are consuming sugar in your nutrition elsewhere. (More about this in the next paragraph!)

  3. Through electrolyte capsules (pill form) - This can be another way to quickly incorporate electrolytes and know exactly how much of each you are putting into your body. However, it is important to consider that taking a pill-form of electrolytes introduces a lot of sodium all at once into the body. You’ll want to make sure you have plenty of water in your system to avoid creating an extremely hypotonic (too salty) environment in your stomach. If you typically have GI issues related to electrolyte imbalance, this can be dangerous.

If you are looking at electrolyte consumption during running, the biggest thing to consider with electrolyte consumption aside from their electrolyte profile is the inclusion of carbs/glucose. Taking electrolytes with sugar helps the transportation and facilitation of those electrolytes within the body. This is because we have sodium-glucose co-transporters that help transport sodium across our cell membranes. Therefore, electrolytes + sugar = faster rehydration.

A very general recommendation from ACSM is to consume 500-700 mg of sodium per liter of water consumed when running. Again, this is extremely variable by athlete and by environmental conditions, so there is no “one-size-fits-all” approach to electrolyte consumption.

Just like nutrition strategy, hydration/electrolyte strategies must be practiced ahead of time to figure out what works best for you. If you have any questions specifically about your hydration and electrolyte consumption, consult a doctor or sports-specific dietitian!


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