( This post is a part of a series sponsored by MESTRENGTH.)

If you’ve ever taken a group fitness class, talked to a nutritionist or visited your doctor, you’ve been told to stay hydrated. Seriously, you should stay hydrated, and you already know that. But do you know how much fluid to take in each day and what, exactly, is all of that H20 and whatever you’re mixing with it is doing for you?

Let’s start with the basics: you need 2-2.5 liters of water each day. Natural hydration council in the UK says that’s specific to your gender. Ladies, drink 2.0 liters each day and gents take down 2.5 liters. Yes, we’re on the metric system here, because, science.

That number of liters moves up the metric scale too if you’re active or exercising. According to Breaking Muscle, for every hour you exercise, one should tack on .5 liters. This is something that is intuitive for a lot of athletes. You work out, you sweat, you get thirsty, you replenish.

But you shouldn’t wait for the thirst to hit you to start to rehydrate. Get on an exercise-based hydration schedule. According to About.com Health, it’s recommended that you get about 15-20 fl oz, two to three hours before exercise, 8-10 fl oz 10-15 min before exercise and drink 8-10 fl oz every 10-15 min during exercise. Pro-tip: use that handy sports watch on your wrist to give you a reminder to drink a little water while you work.

That hydration does a lot for you – much more than quenching your thirst. 

Staying hydrated cools your body in the heat.

Water in your cells absorbs heat from your muscles and sweat helps to dissipates that heat. That means that the loss of water during exercise as sweat is imperative – especially in the heat – to cool you off.

The cooling effect of the fluids you take in can even to help you feel like you’re not working as hard so that you can go longer. Runner’s World quoted a study published in 2008 in Medicine & Science in Sports & Exercise that found that cyclist who “who drank cold beverages before and during their workout exercised nearly 12 minutes longer than those who drank warm beverages.” You can do a lot in 12 minutes.

Staying hydrated helps your heart to work efficiently and to stay healthy.

According to the American Heart Association, if you’re well hydrated, your blood flows more easily through the heart and the blood vessels. On the flip side, if you’re dehydrated, your heart has to work harder to get your blood to the muscles that need it. This results in an increased heart rate. Read: a heart that’s working harder beats more often. Dehydration also is linked to an increased blood pressure, according to Livestrong.

A hydrated body digests food more easily.

Allow me to talk about an unpleasant bathroom thing: constipation. Not drinking enough water can lead to it. Nobody wants to talk about this, but we’re all adults here and everything is better when you’re not having issues … going. WebMD says that staying hydrated “keeps the food you eat moving along through your intestines and it keeps your intestines smooth and flexible, too.” When everyone is regular, everyone wins.

Are we talking about just water here?

No! Your daily hydration levels can come from a mix of things. Natural hydration council in the UK says that 70-80 percent of your daily water intake should come from drinks and the remaining 20-30 percent should come from food. That daily water intake can come from a mix of things – sports drinks like MESTRENGTH, tea and even coffee. Recently, scientists are backing up off of the idea that coffee doesn’t count as hydration. According to NPR, a study in UK showed that that “coffee … provides similar hydrating qualities to water.” Thank goodness, scientists.

Whatever it is you’re drinking, be conscious that the calories in your beverages can add up.

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