What are electrolytes?
Electrolytes are most often used simply as a term for salt, sodium chloride, or sodium. This already presents a language problem, as "salt" is only a term for sodium chloride (NaCl), while "sodium" is just the English term for the element sodium (Na). First, let's clarify some basic principles of physiology.
In general, electrolytes help maintain our cellular functions so that they can operate as intended, for example, muscle cell contractions and the transport of electrolytes into and out of the cell. We have several electrolytes that regulate various pumps in the body and maintain the cell membrane potential, which is a crucial factor for electrolyte transport between different body compartments.
Body fluid is divided into two main parts: intracellular fluid and extracellular fluid. Intracellular fluid consists of all the water and electrolytes surrounded by the cell membrane, i.e., the fluid inside the cell. Extracellular fluid is the fluid outside the cells, which consists of blood plasma, lymph, and interstitial fluid (fluid directly outside the cells). And let's look at what electrolytes are in our body!
Sodium chloride (NaCl) - salt
Salt usually has a bad reputation because increased salt consumption seems to be associated with high blood pressure and other lifestyle diseases. However, salt is very important. Salt is the primary regulator of extracellular volume, and it accounts for about 95% of what is called plasma osmolarity, i.e., fluctuations in the concentration of substances like sodium, glucose, urea, or chloride in the blood. During prolonged intense physical exertion, it is recommended to consume about 300-600 mg of sodium per liter of fluid (or 1.7-2.9 g of salt).
Potassium
Potassium is perhaps less well-known, but it primarily regulates intracellular volume. Potassium interacts with salt, as the sodium-potassium pump regulates their function to a greater extent. Potassium is linked to better health because it helps reduce the risk of cardiovascular disease, partly by lowering blood pressure.
Magnesium
Most people probably know that magnesium is related to sleep. Magnesium primarily functions as an intracellular electrolyte. Magnesium plays an important role in energy production, muscle relaxation/toning, and neurotransmitter secretion. For example, magnesium appears to be linked to better muscle function, better bone density, and better sleep.
Calcium
Calcium is very important for muscle contraction, nerve impulse transmission, bone mass regulation, and fluid balance. If low calcium levels are observed, it is usually a symptom of another underlying condition/deficiency, such as low vitamin D levels, which can lead to cramps or spasms because calcium promotes normal muscle function.
Why do we need to increase electrolyte intake?
Many studies show that electrolyte levels can be low during physical exertion. This can be caused by:
Consumption of hypotonic fluid (i.e., consuming fluid with an electrolyte concentration lower than the extracellular electrolyte concentration).
High sweat rate in relation to fluid intake.
Excessive sweating relative to the maximum stomach emptying rate (affected by many different factors).
Very hot climate (during and outside of training).
Hypotonic fluid intake is usually an attempt to quench thirst with water alone, thereby avoiding the intake of certain electrolytes. This is problematic because it is unlikely to be an effective rehydration strategy compared to drinks that contain many electrolytes and carbohydrates. The addition of carbohydrates appears to further increase fluid absorption and retention.
A study by Maughan et al. tested several different types of drinks (ranging from water and milk to Gatorade) in relation to post-exercise rehydration. The researchers found that skimmed milk was the drink that helped with better rehydration. The reason is likely not the milk itself, but the combination of a large amount of fluid rich in many different electrolytes (salt, calcium, potassium, and magnesium), as well as carbohydrates. This is also recommended in major consensus reports.
Therefore, it would be good to focus on fluid intake that is rich in electrolytes and contains a relative amount of carbohydrates. The amount of carbohydrates probably depends more on the intensity and volume of the training.
Context, context, context
Does this mean everyone should take electrolyte tablets in water regardless of what they do and how much they do? Not necessarily, but if any of the factors mentioned above apply to your training, it might be a good idea to consume electrolytes with food/fluid or as a dietary supplement.
The following are signs that you should pay attention to your electrolyte intake:
You have white spots on your clothing after training.
You sweat a lot during training.
You train in a hot place.
You usually do not know how much fluid you are consuming.
The rule is: the longer or more intense the training, the higher the sweat rate. Therefore, you will also need more electrolytes during or after physical exertion.
However, it is generally a good idea—especially as the weather gets warmer and sweat rates increase—to consume some liquid/food with electrolytes to ensure effective rehydration or hydration during/after training. This can be achieved, for example, with an electrolyte drink, but many electrolytes are also found in chocolate milk, protein shakes, and bananas.
