The science of sweat: running and electrolytes

What do runners and hungover college students have in common?

Gatorade. The answer is Gatorade. 

We wouldn't necessarily recommend this sugary beverage to serious athletes, but there is some truth behind its ingredients. 

Regardless of the cause, electrolytes can help with dehydration. And when used correctly, electrolytes can be your best friend, whether you're recovering from a hangover or trying to set a new PR. 

What are electrolytes? 

Most runners are aware that electrolytes exist, and that they must be replaced after sweating. This is a part of the story, but it isn't the whole truth.

As electrical beings, electrolytes are minerals in our bodies that are interwoven with all our bodily fluids, with the purpose of triggering electrical impulses. As a human, these impulses cause muscle contractions that allow us to function properly and run, too. 

In addition to balancing the body's acid-base balance (or pH), electrolytes transport nutrients into cells and remove water from them. A lack of electrolytes or an imbalance of electrolytes can result in muscle weakness, cramping, mental confusion, and problems with major muscles like the heart. 

RELATED: Ten tips for running in hot weather ☀️

Our bodies contain sodium, chloride, potassium, magnesium, phosphate, bicarbonate, and calcium, all of which are electrolytes that runners need. 

These are the electrolytes and what they do for runners: 


  • Most abundant electrolyte
  • Maintain fluid balance 
  • Helps absorb nutrients 
  • Lack of sodium makes it difficult to refuel/rehydrate 

Pro tip: Runners may be familiar with terms such as hypernatremia (too much salt) and hyponatremia (not enough salt).


  • Second most abundant electrolyte 
  • Maintain fluid balance
  • Maintain body pH
  • Imbalances in chloride cause acidity or alkalinity 


  • Works with sodium as the primary intracellular electrolyte (responsible for cell membranes)
  • Balanced potassium is important for heart function
  • Lack of potassium causes muscle cramps or dizziness 


  • Turns nutrients into energy 
  • Helps with muscle recovery 
  • Cofactor in more than 300 enzyme systems!
  • Fuel will be useless if you are low on magnesium 

Pro tip: athletes carry a much higher risk of magnesium deficiency


  • Reciprocal relationship with calcium (if one increases, the other decreases) 
  • Helps cells metabolize nutrients into energy 
  • Building block for important substances for energy, cell membranes, and DNA 


  • Less well-known electrolyte
  • Made of recycled carbon dioxide not used in regular respiration
  • Keeps body’s pH in balance


  • Controls muscles and manages heart rhythm
  • Too much may negatively affect body systems (kidney stones, joint pain, digestive problems, or headaches)
  • Lack of calcium may cause muscle spasms and weak bones 

The four major electrolytes that contribute to the balance of fluids in the body are sodium, potassium, magnesium, and calcium but this doesn’t mean the others aren’t equally as important.

What happens to your electrolytes when you sweat while running?

Our bodies are very careful about maintaining electrolyte balance. Our kidneys are capable of keeping or eliminating electrolytes based on what we consume in a well-balanced diet with a variety of foods. 

But adding exercise to the equation can lead to significant electrolyte losses in the form of sweat. 

For runners and other athletes, sweating loses a considerable amount of sodium and chloride, so supplementation is necessary to replace these minerals. As we sweat less potassium, magnesium, and calcium it is best to consume adequate amounts of these electrolytes through food.

And no, you cannot just add more salt to your food after running. 

Consuming additional sodium without other electrolytes will cause water retention and disrupts the body's regulation processes. That is why electrolyte drinks with proper balance should be prioritized for running. 

How do runners know how many electrolytes to take? 

For optimal performance, athletes should hydrate before, during, and after their workouts. But knowing how many electrolytes to take (and in what form) is where the real question lies. 

The good news is that for casual runners consuming healthy balanced diets, electrolyte replacement won’t really be an issue. 

For serious runners, those who sweat heavily, are running in extreme heat, or are running for more than an hour, it becomes more of a science experiment. A general rule of thumb in this situation is to consume an electrolyte tablet or sports drink about an hour before running.   

Pro tip: some runners lose more electrolytes in their sweat than others. Consider getting your sweat tested or exploring how to replace your electrolytes

The loss of sodium can range between 200 milligrams and 12,500 milligrams per hour, but it is around 1000mg, on average, which calls for a “sports drink.” Drinking around 14-20oz per hour of exercise is usually sufficient. For longer events and marathons carbohydrate fueling should also be considered, as this amount of fluid intake may not provide enough sugar to keep going.

Sure, carbon shoes are great for performance but have you ever been properly hydrated on a hot run? 

What are the best ways to replace electrolytes that have been lost?

Remember that heat will cause a greater loss of electrolytes (and fluids) in general. When you drink to thirst during workouts or races lasting more than an hour, this should compensate for it, provided that you also consume electrolytes.

If you’re unsure, our expert staff and coaches are always available to answer your electrolyte-related questions in-store or on social media 🤗

We recommend experimenting and choosing an option that works (and tastes) best for you. Here are some of our favourites: 



Electro3 (+caffeine)


Fruit3 Bars

SaltStick Fast Chews

Gu Energy Chews

GU Energy Gels

Carbohydrate+electrolyte drink: