A Quick Primer on Electrolytes for Runners

The claims of electrolytes almost seem too good to be true. Sports drinks promise better hydration, a lower chance of muscle cramps, and less risk of ending up in the med tent. Runners need electrolytes. However, it’s worth diving into the claims and seeing what the evidence says.

Electrolytes are essential for summer running and long-distance running. Some runners are salty sweaters and may benefit from electrolyte supplementation year-round. Other runners may only need them for summer or long-distance races. You are not just limited to Gatorade. Numerous options of electrolyte hydration products are available on the market.  

What are Electrolytes and Why are They Essential for Runners?

Electrolytes are naturally occurring minerals found in your sweat and urine that your body uses to conduct electrical charges. Electrolytes are responsible for muscle contraction and relaxation, fluid balance, and neurotransmission between the brain and muscles.

The electrolytes are the minerals sodium, chloride, potassium, magnesium, and calcium. It is important to replace all of these. However, sodium is the most important of the electrolytes when considering replenishment during runs.

Sodium’s vital functions include fluid and electrolyte regulation in the body, including in the blood. Sodium interacts with hormones including vasopressin (antidiuretic hormone) and aldosterone, which regulate fluid balance in the kidneys. Sodium also maintains proper nerve impulse and muscle contraction via its action on the sodium-potassium ATP-ase pump in muscle cells.

Potassium also aids in fluid balance, particularly in intracellular fluids. Along with sodium, potassium promotes the optimal function of nerve transmission into the muscle cells. Calcium and magnesium interact with key enzymes during glycolysis (conversion of carbohydrates into ATP), glycogenolysis (conversion of stored glycogen into glucose for energy production), and the Krebs cycle. Calcium ions in the muscle cells aid in the action of muscle contraction. Magnesium facilitates calcium’s movement across the muscle cells during muscle contraction.

For daily function, whole foods can provide the necessary electrolytes. However, endurance athletes have higher electrolyte needs, particularly during long-distance races, long runs, and summer training. Those needs further increase during runs due to loss of electrolytes in sweat. Thus electrolytes need to be replaced during runs through easily absorbable means, such as sports drinks or salt tablets. 

Why are Electrolytes Essential for Runners?

On average, most runners generally lose 770 mg of sodium per liter of sweat. Rates of potassium, calcium, and magnesium loss average 195 mg/L, 20 mg of calcium/L, and 10 mg/L, respectively. However, this is truly an average. Some runners lose low amounts of sodium in their sweat, while others lose significant amounts. A 2017 study in the Scandinavian Journal of Medicine and Science in Sport measured sodium levels of experienced marathoners. The low-salt sweaters lost an average of 371 mg sodium/L sweat. The typical sweat group lost an average of 957 mg/L. Sodium losses reached an average of 1597 mg/L in the high sweat group, with some individuals reaching 1839 mg/L. (Like many studies, the sample size included only male athletes.)

Thus, the sodium loss rate varies significantly in runners. Individual electrolyte needs may vary. It often takes trial, error, and experience to understand yours.

You are not going to replace this completely nor do you need to. The optimum goal is roughly half of this (so roughly 400mg of sodium per hour of intense exercise). You do want to be mindful not to overdo the sodium. Too much sodium can cause excessive thirst and GI distress. So, don’t take both Nuun AND Saltstick; however, combining gels and Nuun or Skratch works well for most runners. 

Replenishing electrolytes can offer benefits even if your sodium levels do not drop to a dangerous threshold. Plain water can impair thirst reflux via reductions in plasma osmolality. Sodium in sports drinks enhances thirst and therefore encourages fluid consumption during exercise.

Electrolytes Aren’t Just For Salty Sweaters

A 2011 cross-sectional study in the Journal of Athletic Training found that a majority of long-distance runners preferred water to a sports drink. Some also avoided sports drink due to the calorie count. Real-life coaching experience supports this; both myself and other coaches I know have seen athletes either forget to take or deliberately avoid electrolytes consumption. 

But for long-distance running, electrolytes are essential for both performance and health. Minor electrolyte imbalances can cause muscle cramping and dehydration; severe imbalances can cause nausea, vomiting, confusion, dizziness, and even seizures as symptoms of dilution of the blood (hyponatremia). 

Common misconceptions tend to correlate heavy sweaters with a lack of fitness. While it is true that an unfit athlete will sweat more at lower exertion levels, sweat rate is simply an individual factor. Some runners simply sweat higher volumes and lose more salt in their sweat, even if they are highly trained. According to a 2016 study in the Journal of the International Society of Sports Nutrition, approximately 20% of non-professional marathon runners are salty sweaters – and no individual characteristics or past training predict one’s sweat rate. 

Now, it is worth noting that you want to take in electrolytes even if you are not a salty sweater. According to a 2015 study published in the Scandinavian Journal of Medicine and Science in Sports, while salty sweaters tend to have lower sodium serum levels, any runner is at risk for hyponatremia if they overhydrate and do not replace sodium during a long-distance race. As the study noted though, salty sweaters need to be extra cognizant of taking in higher levels of sodium during exercise. 

Electrolyte Loss and Performance Decline

Electrolytes do support proper muscle function. However, the most significant impact electrolytes have on performance relates to hydration. Repeated evidence indicates that fluid losses exceeding 2-4% of bodyweight can impair performance. The more fluid loss, the more profound the performance decline. At 4-7% of bodyweight lost in sweat, aerobic performance degrades rapidly.

A 2021 article in Nutrients outlines the negative effects of dehydration on endurance performance. Around 2% bodyweight lost, running economy begins to deteriorate. Dehydration thickens the blood, which in turn increases the cardiovascular demands of exercise. Cardiac output drops, which means less oxygen-rich blood reaches the working muscles. 4-5% dehydration will result in reduced VO2max, especially when exercising in the heat.

As described above, electrolytes encourage rehydration during exercise. Their effect on blood osmolality promotes thirst, which drives the athlete to drink more. Many athletes prefer how electrolyte beverages taste and are more inclined to drink them.

In long-distance races, electrolytes can serve as an ergogenic aid (performance booster). A 2016 study in the Scandinavian Journal of Medicine and Science in Sports tested triathletes in the half marathon distance, with a control group (who took placebos) and a group consuming oral electrolyte tablets. The electrolyte group finished an average of 26 minutes faster than the control group. That’s a significant amount of time!

Do Electrolytes Prevent Muscle Cramping for Runners?

The evidence on electrolytes and muscle cramping is presently divided. A 2021 study in the Journal of the International Society of Sports Nutrition concluded that electrolyte intake decreases the incidence of cramping. The researchers also noted that consuming plain water during long-distance running actually makes you more likely to experience muscle cramps. However, a 2022 study in the Journal of Strength and Conditioning Research found no correlation between serum electrolyte levels in athletes who experience muscle cramps.

Hyponatremia and Electrolytes for Runners

When you consume too much water during exercise without adequate sodium, your blood volume can become too diluted. This condition is called hyponatremia and requires immediate professional medical care. Symptoms include nausea, vomiting, dizziness, confusion, headache, and intense fatigue. The longer the event, the greater the risk of hyponatremia if sodium is not replenished.

However, the interaction of electrolytes and hyponatremia risk continues to be studied. The above-cited study on sweat rate in marathoners concluded that higher sodium loss in sweat did not increase the occurrence of hyponatremia. However, those runners also reported higher sodium intake during ad libitum fluid consumption during the race. So, we do not know how plain water consumption could have affected their risk.

For a more in-depth analysis of electrolytes and hyponatremia, this article provides a thorough overview of recent research. If in doubt, take in electrolytes. Even if we don’t know for certain if they prevent hyponatremia, the benefits of electrolytes outweigh the possible risk.

How to Consume Electrolytes

If you are running for less than an hour, you do not need to take electrolytes. For runs and races in the 1-3 hour range, you want to take a hydration mix or electrolyte tablet. For races exceeding three hours, be extra mindful of consuming adequate electrolytes both before and during. Some research suggests that marathon runners with hyponatremia may began in a slightly electrolyte-deficient state

Many runners skip electrolytes because Gatorade upsets their stomachs. However, it is not the electrolytes causing GI upset. For some, it’s the particular sugars used and the artificial coloring and flavorings. There is nothing wrong with drinking Gatorade or Powerade if it works for you. If you find Gatorade causes GI distress, you will want to find an alternative option and carry it with you on your training runs and race day. There are several types of sports drinks and salt tablets that can be used for electrolytes.

Coconut water has become more popular in recent years. A 2017 study in the International Journal of Sport Nutrition and Exercise Metabolism found no significant differences in hydration or time trial performance when comparing coconut water to plain water. The only difference found in a 2012 study in the International Journal of the Society of Sports Nutrition is that runners ingesting coconut water reported more symptoms of GI upset including bloating. According to a 2014 study in Applied Physiology, Nutrition, & Metabolism, the additional potassium in coconut water does not confer any additional rehydration benefits. Potassium is lost in small amounts in sweat compared to sodium. If you prefer coconut water to a sports drink, then use it. However, coconut water is not superior to other electrolyte drinks.

Most electrolyte drinks formulated for exercise will contain carbohydrates. Carbohydrates play a key role in sodium transportation into the muscle cells. Given the carbohydrate recommendations for long-distance running, those extra carbs will only help! 

Some popular options include:

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11 Responses

  1. I have used Tailwind with good success for many years. I did find that even diluted, it sometimes upset my stomach. I’ve had issues with gels too. I just got a sample of Liquid IV to try and I’m looking forward to seeing how it works for me.

  2. This is great information, Laura. I like how you broke it down in an easy-to-understand manner.

    I’m planning to make my own electrolyte concoction. It’s cheaper and I know what’s in it.
    I’m not sure if I’ll succeed – I’ll keep you posted!

  3. Thanks for the info.

    I tend to drink just plain water.

    I eat Gu which does contain electrolytes.

  4. Super helpful, thanks, as we approach summer. I can do the powders better than I can gels, although I love the margarita chews, which I think have some salt. Really need to look into the salt sticks.

  5. I’ve been using Liquid IV lately which I am liking. I fill one smaller water bottle with plain water and the other with Liquid IV for my long runs (and put them in the front of my hydration vest). Adding some electrolytes can really make a big difference, especially on summer long runs!

  6. Electrolytes are so important! I personally love Nuun Hydration too and always have a few tubes in the house. I remember after my very first half marathon I visibly had salt on my face from sweating out so much salt. It’s so important to replenish!

  7. Electrolytes have really helped me with my post-run fatigue! I used to feel terrible after long runs until I discovered the power of electrolytes. And now I take them religiously if I’m out longer than an hour.

  8. Thank you so much for sharing

    Electrolytes have really helped me fight off fatigue, especially post-training. I’ve always felt terrible after a long workout and things changed once I started paying attention to my electrolytes intake. I used to drink just plain water. Big mistake

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