You know you're supposed to replenish your electrolytes after a killer sweat session, with sips like coconut water and sports drinks. But what are electrolytes, exactly? And why do our bodies need them?

This new video from the American Chemical Society breaks down the science behind the crucial salts (yep, they're salts). In a nutshell: Once electrolytes (think calcium, potassium, magnesium, and plain old table salt) are in our bodies, they dissolve into positive and negative charges. These charges have two main functions: Regulating the flow of water in and out of cells, and sparking nerve impulses. 

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Without electrolytes, "our cells would shrivel up and die, or burst from being too full," the clip's narrator explains. And those nerve impulses electrolytes control? They keep our bodies functioning properly—you know, "our hearts beating, our lungs breathing, and our brains learning." So there's that.

When you work out, electrolytes get deposited into sweat glands. Water follows the electrolytes (thanks, osmosis), and as the glands fill up, they release the salty mix onto your skin.

The water then evaporates, which makes you feel cooler—and you're left with that salty taste on your skin (don't act like you don't know what we mean).

As for why fitness instructors are always reminding you to drink up after class, it's because losing too many electrolytes can mess with your blood pressure, breathing, and more. 

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All this talk about the mega-importance of electrolytes might having you craving a Gatorade. But here's the thing: Unless you're a pro athlete, you're probably getting a sufficient amount of electrolytes through your regular diet—no neon-colored beverages necessary.

And who needs the sugar in most sports drinks? As the narrator points out, "if you’re doing a half-hour of cardio, a single bottle of the stuff will give you all the calories you just worked off." 

The flick's take-away advice: Stick with water to hydrate, and save the sports drinks for your next marathon.