Salt Tablets for Runners? Electrolyte Needs & Supplementation in Running Explained

Last Updated on January 22, 2022 by Heather Hart, ACSM EP, CSCS

Running is anything but a simple sport. There is a plethora of training and racing methodology, information, resources, and advice (both good and bad) floating around the running community. Add to it a constantly evolving market of shoes, technology, and supplements being advertised to runners. Sometimes, it can be hard to understand.

For example, when talking about training and racing nutrition and hydration, you may have heard about things like electrolyte powders or salt tablets for runners. But what are these endurance specific electrolyte supplements? How do they work? Can’t you just drink some Gatorade? Further, do you really need these supplements? Don’t we take in enough salt in our diets already?

(It’s a very valid concern and question, and we’re going to talk about it)

In this post, I aim to cover electrolyte needs for runners, talk about whether or not supplementation actually works, as well as break down various electrolyte supplement products that can be implemented in training or on race day.

Note: if you are specifically training for ultramarathon distances, read this post first. Then, head over to my post “Electrolytes & Ultramarathons: A Controversial Science?”. Because, in short, research shows the considerations for requirements and supplementation strategies do change over ultramarathon distances.

Disclaimer:  This post was carefully researched and written by Heather Hart, a certified Exercise Physiologist. It is for informational purposes only and should not be construed as an individual prescription or medical advice.  Please consult a physician or qualified nutrition expert for individual electrolyte replacement advice.

Electrolytes: the Basics

I get it…not everyone gets as excited about diving into the science behind running as I do. But I also think it’s important to have a general understanding of why we do what we do in the running, training and racing world, rather than say, blindly taking a salt tablet or sports drink just because some running coach online told you to.

So before we dive into the specifics of electrolyte needs for runners, I want to give you a run down of what electrolytes are, where they come from, how our bodies use them, and why being aware of electrolyte balance is integral for running success. I promise to keep it fun and hopefully easy to understand.

What are Electrolytes?

When you hear the term “electrolyte”, chances are your mind immediately jumps to things like Gatorade or Pedialyte.

Technically speaking, electrolytes are substances that dissociate in solution and have the ability to conduct an electrical current (or, particles that carry a positive or negative electric charge). These substances are located in the extracellular (outside of your body’s cells) and intracellular (inside of your body’s cells) fluid.

When we are talking about nutrition and human physiology specifically, electrolytes are essential minerals that are vital to many key functions in the body, and can be found in blood, urine, and sweat. The aforementioned electrical charge is responsible for things like muscle function, fluid balance, and neurotransmission between the brain and the rest of your body. All important things that help your body actually run.

The major electrolytes within our body are:

• Sodium
• Potassium
• Chloride

Other necessary electrolytes include:

• Calcium
• Magnesium
• Phosphate
• Bicarbonate
• Sulfate

We get our electrolytes through the food and drinks that we consume on a daily basis. However, athletes (especially long distance/endurance athletes) tend to supplement higher doses of electrolytes while training and racing, as a means to try and replace electrolytes lost in sweat (more on this soon).

Why does our body need electrolytes?

In the simplest term: electrolytes are important for maintaining homeostasis within your body. More specifically, electrolytes are required for various bodily processes, such as:

• Nervous system function: allowing the brain to send electrical signals through your nerve cells to communicate with the rest of your body
  
• Muscle function: both calcium and magnesium are required for muscle contractions to occur
  
• Hydration status: sodium helps regulate proper amounts of water both inside and outside of your cells
  
• Maintaining healthy pH levels within your body, creating an optimal internal environment 

How do we lose electrolytes?

Since electrolytes are found in bodily fluids, our bodies excrete electrolytes through…you guessed, bodily fluids. On a day to day basis, excretion of electrolytes occurs mainly through the kidneys into urine, with lesser amounts lost in sweat and in feces.

And while hopefully not a day to day occurrence, it’s important to know that vomiting or diarrhea will cause a loss of electrolytes as well.

What can happen when there is an electrolyte imbalance?

Electrolyte imbalances can happen for a number of reasons, but we’re going to focus on the running specific causes in this post.

Most people are familiar with the concept of dehydration. This occurs when inadequate amounts of water are consumed to compensate for fluids lost through normal bodily functions (urine, sweat, etc.) It can result in a condition known as hypernatremia, or when the sodium level in the blood becomes abnormally high because water loss exceeds sodium loss.

But, equally as important is hyponatremia. Hyponatremia is a condition in which sodium (salt) levels in the blood become abnormally low. In the case of running, this can often happen because over overhydration, when a runner consumed too much water. While hypernatremia can be dangerous, hyponatremia has the potential to be deadly.

When there is an electrolyte imbalance (from both over or under hydration), your body can experience a slew of negative side effects, from irregular or fast heart rate, to muscle cramping, nausea/vomiting, muscle weakness, irritability, headaches, confusion, and even convulsions or seizures that can lead to death.

Electrolytes and Running:

Now that you have a basic understanding of what electrolytes are, as well as their important roles in our bodies, let’s talk specifically about electrolytes and running.

Signs of Electrolyte Imbalance While Running:

Common symptoms of electrolyte imbalances while running include:

• Muscle cramping
• Headaches
• Muscle weakness
• Unexpected fatigue/lethargy
• Nausea/upset stomach
• Irregular heartbeat
• Rapid heart rate
• Dizziness/confusion

It’s really important to note here that these symptoms are similar for both hypernatremia AND hyponatremia. Frequently, when runners experience things like headaches or nausea, they tend to assume they are dehydrated. However, studies show that reported incidences of Exercise-Associated Hyponatremia (EAH) are between of 5-51% (and in one study, upwards of 65% [5]) following endurance events where athletes are screened, with marathon runners, ultramarathon runners, Ironman athletes, long-distance backpackers, and military service members most commonly affected (3).

The history of rehydrating and electrolytes while exercising:

• Prior to 1969, athletes were advised to avoid drinking during exercise. It seemed to have stemmed from advice given to and from Olympic marathon runners of the early 1900’s that drinking water could be detrimental to performance.
  
• In 1969, a paper by Professors Cyril Wyndham and Nic Strydom, titled “The danger of an inadequate water intake during marathon running”, argued that marathon runners should be allowed to drink fluids in order to prevent heat stroke.
  
• 1969: Gatorade started to be marketed in the US, and it was designated the official sports drink of the NFL. Aided by these commercial interests and the above paper, the idea began to be spread that drinking before thirst was necessary in order to prevent heat stroke. 
  
• 1969: American exercise physiologist, David Costill performed a research study on four top marathon runners. The subjects ran for 2 hours on an indoor treadmill while they drank either nothing, a Gatorade solution, or water at a rate of 100 milliliters every 5 minutes (1.2 L/hr). In short, the study did not find that runners performed better with Gatorade vs. water, but did find that water vs. no water resulted in an overall 0.7 degrees Celsius lower body temperature. The research was funded by Stokely-Van Camp, the original owners of the Gatorade brand.
  
• In 1975 The American College of Sports Medicine asked David Costill to write the first drinking guidelines, based on the above research.
  
• In the early 1980’s, Dr. Timothy Noakes, professor of exercise and sports science and marathon runner himself, started campaigning and writing articles, shared in Runner’s World and elsewhere, saying you should drink as much as you can, whenever you can, while running.
  
• 1981 the first case of exercise-associated hyponatremia was reported in a female runner during the Comrades Marathon.
  
• Four years later, that case of hyponatremia and another three similar cases were reported in a paper titled “Water intoxication: a possible complication of endurance exercise“, written by Dr. Noakes and colleagues.
  
• Between 1996 and 2013, ACSM changes their position statements on hydration strategies for athletes four times, from stating in 1996 that “athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated” to the current statement: ” Fluid replacement strategies should be individualized and take into consideration environmental conditions, exercise intensity and duration, pre-post body weight, body size, and other individual characteristics“

With the shift in recommendations from “drinking as much as you can” to understanding that fluid replacement must not result in an electrolyte imbalance, sprang the concept that replacing electrolytes was necessary too. Supplementation with sports drinks and other electrolyte replacement products became a popular way to, in theory, prevent hyponatremia.

Electrolyte Supplements…Do They Really Work?

Well, my friends, this is a great debate in the world of exercise science. For decades we’ve had plenty of supported, documented research telling us that that electrolyte supplementation during exercise is necessary as a part of the rehydration process.

On top of that, we’ve routinely been told, both by experts in the field and a barrage of marketing from supplement and sports drink companies, that electrolyte supplementation can help us avoid a whole slew of other “not really what I was hoping for on race day” issues, such as cramping and gastrointestinal distress, as well as help us with performance.

And this belief is common. Researchers from the Western States Run Research Committee found that 90%–96% of runners at the 2011, 2013, & 2014 Western States Endurance Run 100 Mile Ultramarathon used sodium supplements (4).

Electrolyte supplementation, with a heavy focus on replacing sodium, is a well known and frequently practiced strategy among runners.

However, there are dozens of research studies and scientific papers written by scientists who don’t necessarily believe that electrolyte supplementation, specifically when it comes to sodium replacement.

(For more on this, dive into my ultramarathon specific post , that covers much more on the on this specific aspect of electrolyte supplementation.)

Nevertheless, in addition to the research showing electrolyte supplementation while running is necessary, endless anecdotal evidence from runners who believe that electrolytes do help them prevent cramps, stomach issues, and maintain a healthy fluid level, also exists. Further, as you’ll see below, the electrolyte supplement industry is quite large, with endless replacement products available specifically for runners and other endurance athletes.

Individual Electrolyte Requirements:

During exercise, like running, sweating is the main cause for significant loss of electrolytes, especially of sodium and chloride. According to the American College of Sports Medicine, on average people lose between 0.8 to 1.4 liters (roughly 27.4 to 47.3 oz.) of sweat, or 2 to 6 percent of their body weight during exercise. (1) The amount of total fluid an individual sweats per hour is called their sweat rate.

Further, we know that electrolytes are lost through sweat. But how much? Again, on average, runners lose about 800mg of sodium, 195 mg of potassium, 20 mg of calcium, and 10 mg of magnesium per hour of running. (1)

Specifically regarding sodium, research has found that the sodium concentration in sweat can vary among individuals from 200 to 2,000 mg/L (2)

But we know that averages are not accurate for everyone. To make this even more complex, individual sweat rates and sweat composition may vary based on factors such as:

• temperature
• humidity
• elevation
• your current fitness level
• hydration levels
• and more.

How to determine your sweat rate:

Determining your personal sweat rate can easily be done at home during a regular training run. Again, it’s important to note that sweat rates can vary based on all of the factors above. If you are truly wanting to understand your personal sweat rate, I recommend performing this test during multiple different weather (temperature, humidity) scenarios to give you a better understanding of how your body responds to different environments.

This post is long enough as is, so I’m going to send you to this link to instructions for how to perform a sweat rate test

Cons of the at home sweat rate test:

Of course, there are downsides to these types of tests.

1. A sweat rate test will NOT tell you the concentration of electrolytes in your sweat.
2. This at home/self test method is not 100% accurate.
3. It should be noted that trying to replace 100% of your lost fluid can actually result in overhydrating (hyponatremia)

How to determine electrolyte concentration in sweat:

If you’re curious to truly learn the concentration of sodium and other electrolytes lost in your sweat, a sweat analysis test can give you the answers that you seek.

There are a couple of different options available to athletes, and may vary greatly in both availability and of course, cost. Of course, if you are an elite athlete and have access to scientists and doctors, more accurate and slightly invasive tests are available (such as blood tests, or the Whole Body Washdown protocol).

Non exercise sweat diagnostics:

One of the testing diagnosis protocols for patients with Cystic Fibrosis includes a non-exercise sweat test. Those with Cystic Fibrosis lose an extremely high amount of salt (sodium chloride) in their sweat. With this method, in a lab setting chemicals are applied to the skin to mimic the effect of certain neurotransmitters that stimulate the sweat glands and allow sweat samples to be collected ‘at rest’.  The sample is then analyzed to determine the concentration of sodium, chloride, and potassium in the patients sweat.

This method has become increasingly popular with athletes as well.

Pros of non exercise sweat diagnostics: This is likely going to be one of the most accurate ways to determine the concentrating of electrolytes in your individual sweat

Cons of non exercise sweat diagnostics: Since this is a non-exercise sweat test, the results will not take into account any variability based on environmental factors, such as heat, humidity, or altitude. Another con for most athletes will simply be the availability of this type of testing, as well as any costs associated with the test.

Sweat patch testing:

There are a few different options available for sweat patch testing. But the method remains generally the same. Small patches are stuck to the skin and left on during exercise, with sweat soaking into the material as the runner exercises.

In some cases, the patches are then removed and sent off to a lab where the sweat extracted and then analyzed to determine electrolyte composition.

Newer options on the market, such as the Gx patch system from Gatorade, give you instant at home readings. The Gx patch is worn during exercise, and measures both sweat rate and sodium and chloride lost. You take a picture of the patch, and then upload it to the Gx app. The app uses algorithms developed by Gatorade over the past decade or so to estimate (keyword here) total body sweat rate and sodium losses based on sweat collected from a small area of the forearm.

Pros of sweat patch testing: Easier to do on your own time, you don’t need to have access to a lab. Can be performed in a wide variety of environmental scenarios (vs. a laboratory setting.) More cost friendly than testing.

Cons of sweat patch testing: There is definitely room for error with sweat patch testing. In the case of a patch that is sent away to a lab, there is a possibility of sweat evaporating from the patch before it is analyzed, as well as the possibility of contamination. In the case of the Gx patch, the technology is still at best, an “estimate” and not an actual, true reading.

Electrolyte Replacement Strategies for Runners:

So…is there a specific goal or suggestion for electrolyte replacement?

The American College of Sports Medicine give general recommendation of aiming to consume sodium in concentrations of 500–700 mg·L^− 1 of fluid when running for more than an hour.

But, if you’ve gathered ANYTHING from what I’ve written thus far, it’s that fluid and electrolyte replacement strategies truly do vary from person to person, and will likely even vary from race to race.

Bottom Line: Trial and Error is Necessary

Feeling overwhelmed yet? Trust me, I get it. I wish you, my readers, could see the nearly 40+ tabs I currently have open in my browser full of research articles regarding electrolyte replacement strategies for endurance athletes.

The best thing you can do as a runner is to experiment with electrolyte supplementation and rehydration during your training runs, while keeping all of the known information stated above in the back of your mind as a general guideline to start with.

Further, be cognizant of the fact that overhydrating is very common among distance runners. Electrolyte supplements are not a guarantee that you will not develop hyponatremia, so it’s still important to be cognizant that your fluid replacement rate does NOT exceed your fluid loss rate (basically: don’t drink more than you sweat/pee out.)

Salt Tablets for Runners: Supplementation Options

Now that we’ve got through ALL of the science of electrolytes, let’s talk about what sort of electrolyte supplements exist.

Types of Electrolyte Supplements:

If you aren’t already aware, let me be the first to tell you that there is NO shortage of electrolyte supplements available for purchase, all designed with endurance athletes in mind. This, too, is quite overwhelming, especially when each company markets their product as the “best” option.

You can find electrolyte supplementation products in various forms. It’s important to note that not all products are identical across brands. For example, the electrolyte profile in one powdered drink brand may vary greatly from another. One may contain some form of sugar (calories) and can double as a fuel source, while others may be artificially sweetened. More on that soon, but first, let’s go over the types of supplements:

Pre-made Sports Drinks:

You’ve seen them, you know them, you probably drank them during 6th grade soccer practice. Gatorade, Powerade, the stuff you can find in any grocery store.

Pros: you can find these almost ANYWHERE.

Cons: the electrolyte content of these drinks is typically not nearly high enough to properly replace the electrolytes lost for runners. Further, these drinks tend to be really high in sugar, and can cause gastrointestinal stress in many.

Capsules:

Literally, pills of electrolytes in powder form. These are most likely what people are referring to when they talk about salt tablets for runners. Popular products include Hammer Endurolytes, GU Roctane Capsules, or SaltStick Caps.

Pros: A quick way to get a heavy dose of electrolytes. Can keep electrolyte supplementation separate from fluid consumption(hydration) and fueling (calories).

Cons: If you hate swallowing pills, this one isn’t going to work for you. Can also cause an upset stomach for some athletes.

Chews

Remember the candy Sweet Tarts from your childhood? (Or perhaps from your kid’s Halloween bucket? Hey, I collect my mom candy tax too, I’m not judging). They are kind of like that…only saltier. A chewable tablet to give you a quick and concentrated dose of electrolytes. A popular product currently on the market is SaltStick Chews.

Pros: Chewable, ideal for those who don’t like to swallow pills. Keeps electrolyte supplementation separate from fluid consumption(hydration) and fueling (calories)

Cons: Tend to have a lower dose of electrolytes per serving. In particular, the recommended dosing for SaltStick Fast Chews is two chews every 15-30 minutes of activity. At about $0.25 per chew, that can be a costly option.

Powders

Powders are designed to be added to water or another drink of your choice in order to combine electrolyte supplementation with rehydration. They may or may not contain calories (energy) to be used as a source of fuel in addition to a source of electrolytes. Common brands include Liquid IV (hydration only) and Tailwind Endurance (hydration and fuel).

Pros: Allows you to consume electrolytes while also working on fluid replacement.

Cons: Electrolyte concentration can be wildly variable if you don’t follow instructions closely. Many products will tell you to add to a specific amount of ounces, but mid run or race, do we pay attention? Over diluting the drink can lead to overhydrating, which can lead to hyponatremia.

Plus, powders can be a huge pain in the butt to try and mix mid run or race.

Electrolyte Race Day Pro Tip: When it comes to racing, if you’re using powders or sports drinks, you’ll want to make sure that you have a bottle with only water along with a bottle with water + electrolytes as there are times when the body will only want water.

Dissolvable tablets

Dissolvable tablets are essentially compressed powders that also designed to be added to water or another drink of your choice, however come in a much easier to carry (and probably less messy) form. Popular brands include Nuun, GU, SIS

Pros: Portable and convenient!

Cons: Similar to the powders, there is definitely room for user error in over or under diluting the concentration of electrolytes to fluid. Further, many of these tablets can make your drink slightly effervescent, which can cause gastrointestinal stress while running (and can cause a ton of pressure in your water bottle, resulting in a bit of a drink explosion when you finally open it.)

Other? There’s more?

Yeah, there’s more.

Some less common products on the market include things like BASE Performance Salts – an electrolyte replacement product that is crystalline in nature, like actual “salt”. According to the company’s instructions for use, you lick you finger, dip it in the “salt”, and then lick it off your finger. I’m not kidding.

Another product I found in my digging is a liquid concentrate that you are supposed to add to your drink of choice.

With or Without Calories?

Now, with almost all of the products above, we need to also take into consideration that electrolyte supplements can be stand alone, or may be mixed with some sort of carbohydrate to meet your fueling needs as well as your electrolyte needs.

Two popular examples include Tailwind Endurance Fuel, which contains 100 calories per serving, and Skratch Labs Sport Hydration mix, which contains 80 calories per serving.

We do know that adding glucose (a simple sugar) to electrolyte replacement supplements can help your body better absorb sodium (Na+/glucose cotransporter). This faster absorption of sodium can aid in faster water absorption through osmosis (water moving from areas of lower electrolyte concentration across cell membranes to areas of higher electrolyte concentration). This can be one of the noted benefits of an electrolyte replacement that does contain carbohydrates.

Be Cognizant of Electrolyte Profiles in Products:

It’s important to note that not all electrolyte supplements are created equally. Take a peek at the slides below, comparing the electrolyte profile of some popular supplements used by ultramarathon runners. You’ll notice that they vary greatly not only in amounts of specific electrolytes (for example, some contain as high as 1,000 mg of sodium per serving, while others contain as little as 100 mg) but the ratios of various electrolytes, as well as what electrolytes are included, vary as well.

Which product you choose will certainly be a personal preference, and may even vary throughout the year as sweat rates change with environmental conditions.

For example, if you have a sweat analysis test done and learn that you are a heavy sweater, AND tend to lose high amounts of sodium in your sweat, you’re going to want to opt for a product with a higher sodium content.

Further, you will want to take into consideration your day to day diet as well. If you eat a diet high in sodium, you may be fine with a supplement featuring a lower sodium content. However, if you eat a low sodium diet, you may opt for a supplement with a higher sodium dose.

As with all hydration and nutrition methods in the sport of ultrarunning, practice makes perfect. Do not hesitate to try multiple brands and options, until you find something that works well for you.

Electrolyte Timing: Does it Matter?

The idea is that you take electrolytes at intervals that will help maintain a proper electrolyte/fluid balance within your body. Each product is going to have specific dosing and timing recommendations, so be sure to read labels carefully. Further, you may find with experimenting that your personal strategy may vary slightly from what is recommended on the packaging.

I reached out to Wilfredo Benitez, MScN, M.Ed. sports nutrition expert and head coach of On Pace Wellness, to help us better understand this one.

“Athletes often use electrolytes during training, but they can be taken before training, after training, or at any other time to improve hydration.” says Coach Will “I often recommend people drink electrolytes after hard or long efforts to replace important electrolytes that will help increase hydration post-training.

Beyond this, there isn’t exactly an ideal time as to when to drink either, but definitely be sure to have electrolytes handy to add to your water for if you start to feel symptoms of dehydration (e.g. muscle cramps, darker urine, lower heart rate, and more).”

Electrolyte Supplementation on a Daily Basis?

If you’re paying attention to the endless marketing towards endurance athletes, you will see that there are a number of products geared towards “everyday use”, and not just for running and training. Do we truly need to supplement electrolytes on a day to day (not race) basis? Or can food account for daily electrolyte needs? 

Will: “No, we certainly don’t need these products on a day-to-day basis. We can meet our daily electrolyte needs from our liquid and nutrition intake, as long as we’ll eating well and a well-varied diet, full of important whole foods from grains, legumes, fruits, vegetables and more. “

Electrolyte & Running Myths:

I asked Will about some common myths or electrolyte mistakes runners tend to make. Here’s what he had to say:

Will: “The biggest mistake I hear is that people take the general recommendation and think that salt is the enemy. “

(For reference, the Dietary Guidelines for Americans recommends adults limit sodium intake to less than 2,300 mg per day.)

Will continues: “Sure, I don’t think people need to be having salty food all the time, but endurance athletes need much more salt than the general person. If you’re drinking a lot of water but not getting in salt from electrolytes or not adding salt to foods, you are missing a very important step to fluid balance.”

More than just sodium:

Will also makes a point to share that we need to be concerned about more than just sodium: “Taking that a step further, another mistake is thinking that sodium is the only electrolyte that matters. An electrolyte drink is more than just salt and water. You need potassium, magnesium, and calcium as well so be sure to emphasize foods with these nutrients on a day to day basis, and if you’re making your own electrolytes, don’t forget that you’ll want to include these minerals. Fortunately, electrolyte products for purchase are well formulated these days so you should be in the clear here!”

Electrolytes & Running: Key Takeaway Points

This was indeed a long post, and if you read the entire thing, I applaud your resilience and endurance. But on a serious note, I certainly hope you were able to better understand the very important role electrolytes play in our bodies, especially when it comes to the sport of running.

If you’re feeling a bit overwhelmed with all of this information, I completely get it. So I’m going to leave you with some closing points and key takeaways to remember:

• Electrolytes are important minerals we obtain through food and drink, that our bodies need to function properly.
  
• When running, we lose electrolytes mainly through sweat, but also through urine.
  
• The amount of sweat AND the amount of electrolytes in the sweat that are lost per hour of running varies from runner to runner, and can vary run to run based on numerous internal and external factors.
  
• Electrolyte imbalances can cause a number of negative physical side effects that range from unpleasant to downright dangerous.
  
• Dehydration is not the only concern of an electrolyte imbalance. Hyponatremia (an overabundance of water/low sodium levels) can be equally, if not more, dangerous for runners. Further, many of the symptoms between the two are identical.
  
• Electrolyte replacement has traditionally been recommended for runs greater than an hour.
  
• However, emerging research suggests there may be no correlation to supplementation of sodium, and development of hypernatremia, hyponatremia, prevention of cramps, or nausea.
  
• Exact electrolyte replacement amounts and strategies will vary from runner to runner.
  
• Not all electrolyte replacement products, such as salt tablets for runners, are created equally.
  
• The best replacement strategy is one that addresses your individual needs, thus, experimenting with hydration and electrolyte supplementation during training runs is vital.

Whew. And there you have it, electrolytes and running in a not so small nutshell. If you have any questions at all regarding this post, please leave a comment below. And, if you’re an ultramarathon specific runner, or considering running an ultramarathon in the future, I encourage you to visit this post next: “Electrolytes & Ultramarathons: A Controversial Science?“

Resources:

1. American College of Sports Medicine, Sawka, M. N., Burke, L. M., Eichner, E. R., Maughan, R. J., Montain, S. J., & Stachenfeld, N. S. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and science in sports and exercise, 39(2), 377–390. https://doi.org/10.1249/mss.0b013e31802ca597
   
2. Baker, L. B., Barnes, K. A., Anderson, M. L., Passe, D. H., & Stofan, J. R. (2016). Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. Journal of sports sciences, 34(4), 358–368. https://doi.org/10.1080/02640414.2015.1055291
   
3. Buck E, Miles R, Schroeder JD. Exercise-Associated Hyponatremia. [Updated 2021 Sep 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK572128/
   
4. Hoffman, M. D., Stuempfle, K. J., & Valentino, T. (2015). Sodium Intake During an Ultramarathon Does Not Prevent Muscle Cramping, Dehydration, Hyponatremia, or Nausea. Sports medicine – open, 1(1), 39. https://doi.org/10.1186/s40798-015-0040-x
   
5. Seal, A. D., Anastasiou, C. A., Skenderi, K. P., Echegaray, M., Yiannakouris, N., Tsekouras, Y. E., Matalas, A. L., Yannakoulia, M., Pechlivani, F., & Kavouras, S. A. (2019). Incidence of Hyponatremia During a Continuous 246-km Ultramarathon Running Race. Frontiers in nutrition, 6, 161. https://doi.org/10.3389/fnut.2019.00161