Whether you’re training like a fighter or simply pumping iron at Las Vegas gyms like a Las Vegas Athletic Club, you’re going to work up a sweat. You might even reach for a replenishing sports drink, which promise to send electrolytes coursing through your depleted body. But what are electrolytes, and what is their purpose? Here’s a quick guide:

What they are: An electrolyte is simply any ion (that is, an electrically charged atom or molecule) that can allow electrical signals and water to travel through the many permeable cells in your body.

Most common types: Sodium, chlorine, potassium, calcium, and magnesium

Why they’re important: With each liter of sweat, about 1.5 grams of electrolytes escape through the pores. This means that if you’re sweating copiously and drinking only water to compensate, you can effectively dilute your internal electrolytes.

Who needs them: Marathon runners and other endurance athletes, especially, since their electrolyte depletion leaves them susceptible to conditions like hyponatremia. Some of the best gyms in Vegas have varied their approach to target certain fitness goals—as with intense CrossFit interval training or Cobra Kai Jiu-Jitsu, which molds lean, muscular competitors through Brazilian jujitsu and other martial-arts classes—so it’s more likely you’ll lose a good amount of electrolytes as you work out.

How to get them: Fortunately, our bodies typically maintain their electrolyte balance through normal dietary intake. Table salt, for instance, is made up of sodium and chlorine ions. So even if you work out for an hour every day, a healthy diet and sufficient hydration should keep your body amply charged with electrolytes. Most Las Vegas gyms are wise to the importance of electrolytes, so you can usually get them in the form of drinks or snacks right on site.