Hydration and Working Out: An Athlete’s Guide to Water, Electrolytes, and Optimum Performance

When the body is consistently in a happy state of hydration, life is good. Your skin is clearer, you have more energy, and your workout performance is solid. Your hair might even be shinier. 

It seems so simple.

Yet, proper hydration is one of the biggest training puzzles for a lot of high-performance athletes — particularly runners. Even for the average active person, figuring out how much water you need, and when, can be confusing (at best). There’s conflicting advice everywhere.

We’ve done our best to sort through all that information and distill it down (see what we did there?) to give you the ultimate guide on hydration.

What Is Dehydration?

Simply put, dehydration is when your body doesn’t have the fluids it needs to function properly. When you’re operating with sub-optimal levels, your heart, your muscles, and even your brain are feeling the strain.

Dehydration is a fairly common occurrence, especially in the summer months. It’s easy to get wrapped up in having fun and forget to drink water, or to be caught running errands without a water bottle to sip.

Symptoms of Dehydration

The most common symptoms of dehydration are headache, dizziness (think headrushes when you stand up), stomach ache, and dry mouth. In severe cases, overheating or fainting may occur. If you’re dehydrated during your workout, you might find that you fatigue faster, have a higher heart rate than normal, or are having a hard time staying cool enough (but more on that later).

Having less water in your body makes your blood volume lower, causing your heart to work harder in order to keep all your organs supplied with blood. It also creates challenges in regulating temperature – it’s hard to sweat when there’s no liquid to spare.

What is Hyponatremia?

On the opposite end of the spectrum from dehydration is hyponatremia, which occurs when you have too much water in your system. From another point of view, the concentration of electrolytes in your body is too diluted. This disrupts the sodium balance in your body, which in turn can affect the ability of your muscles to function properly.

For most people, it’s difficult to consume enough water in a short enough period to trigger hyponatremia. However, if you participate in long, highly taxing exercise, you may be at a higher risk. The condition is most commonly experienced by endurance athletes who participate in workouts exceeding 90 minutes in length, such as ultra-runners or cyclists.

When you sweat, your body is losing electrolytes. During long workouts, if you’re only replenishing water, you run the risk of over-diluting the concentration of sodium, potassium, and other important nutrients in your body. The first signs of hyponatremia are nausea, vomiting, headache, fatigue, and muscle cramping.

How Does Hydration Affect My Workout?

Being hydrated is (obviously) the best scenario for working out. But what happens if you’re not, and how do you know the difference between run-of-the-mill fatigue and performance-altering dehydration?

Effects of Dehydration on Athletic Performance

When you’re dehydrated during a workout, you’re amplifying all the normal symptoms by placing your body under increased stress. If you’re feeling lightheaded on top of your normal fatigue, look for the following symptoms:

You might notice that your heart rate is hovering above average – with less blood to move through the body, the heart is forced to move it through your system faster.   

You’ll also have a harder time regulating your body temperature. Without adequate fluid stores, you have less available to sweat out, diminishing the efficiency of your body’s natural cooling system. If your body has to choose between oxygen and sweating, it’s going to choose oxygen, resulting in a hotter, harder workout for you.  


If you’re snacking during your workout, you’re more likely to experience nausea if you’re dehydrated. Without adequate fluid, the stomach slows down the passage of food into the small intestine, resulting in cramping and discomfort. If you notice your normal snacks aren’t sitting well, look at your water bottle before ditching a tried-and-true fuel source.

How Do You Know If You’re Dehydrated While Working Out?

There are a couple handy tests to determine your hydration levels mid workout. Note: none of these are super-scientific or faultless; think of them like check in points. You should still ultimately pay attention to how you’re feeling and performing against your average.

The color of your urine can be an indicator of dehydration as well; aim for urine to be clear or the color of diluted lemonade. If the colors deepens and starts to look more like apple juice, this is a surefire indicator that you need more fluids. (A note here: multi vitamins, certain vegetables, and other dietary factors can also affect the color of your urine to a more intense yellow).

Hydration and Electrolyte Levels

When you’re low on electrolytes, you’ll experience symptoms similar symptoms to dehydration, like fatigue, lightheadedness, and irritability. Super helpful, right? If you’ve been participating in strenuous activity and you know you’re keeping up on your water, electrolyte depletion might be to blame.

The biggest clue that you’re depleting your electrolytes over your water is cramping. Without adequate stores of potassium, magnesium, sodium, and calcium, your muscles can’t contract (and relax) properly. 

How Much Water Should You Drink?

This is where the research gets even more confusing – there’s no one-size-fits-all, perfect, just do this answer. Recommendations vary by exercise level, altitude, temperature, and a whole host of other factors. And of course, every body is different, so even if you find a straightforward explanation, that doesn’t mean it’ll work for you. As with anything exercise and nutrition related, there’s an element of trial and error while you dial in your personal formula.

Drinking Water at Rest

Water in your day-to-day life lays the foundation for your hydration level when you’re exercising. If you don’t lay a strong foundation throughout the week, you’ll find yourself struggling to keep up when you head into sweat sessions.

You probably grew up hearing about the 8×8 Rule, which states that you should consume 8, 8-ounce glasses of water each day (or 64 oz total). This is a great place to start, but it can still be a lot for smaller or less-active people. The other loose guideline that makes a good starting goal is to consume half your body weight (measured in pounds) in ounces of water each day. This may be higher or lower than the 8×8 rule depending on your stature.

Pick a goal and stick with it for a few weeks to see how you feel. If you’re upping your water intake, you’ll probably be running to the bathroom more than usual in the first few days, but as your body adapts, this should happen less frequently. If you’re still making frequent trips after a couple of weeks, adjust the amount of water down and see how you feel.

Drinking Water While Running

Heading into your runs (or bike rides or swims or lifting sessions) is a slightly different story. If you’re keeping up on your hydration during the day, you shouldn’t need to chug water before you head out. Instead, aim to drink a glass or two of water in the 90 minutes before your workout. This way, you avoid frequent bathroom breaks and the dreaded sloshing-stomach feeling.

While you’re exercising, you should be replenishing the water you’re using. Many sources recommend 4-6 ounces of water for every 20 minutes of activity (or 8 ounces for more strenuous work), which equates to about 18 ounces per hour (or half a liter).

If you have trouble remembering to drink during your workouts, set a time to remind you to sip on water every 10 minutes, or take a drink in between sets if you’re doing interval work. More frequent, smaller sips will probably sit better than chugging once or twice an hour.

If you’re exercising for more than 90 minutes at a high intensity, you’ll want to consider adding an electrolyte supplement to your water source. Many workout supplements (such as gels or chews) will have sodium and other electrolytes in them; if you’re fueling up during your long workouts, you’re probably already covered. Similarly, most sports drinks provide electrolyte supplementation.

As with all advice, this is a starting point based on averages; see how you feel at these numbers and adjust up and down as needed. Remember to pay attention to how recovery feels as well as your workouts — it’s just as important to performance-based training as the workout is.

Drinking Water During Recovery

In recovery, you’ll want to follow your normal hydration guidelines and add as much as your body is asking for. Simply put, if you’re feeling thirsty, drink.

If you’re looking to get precise about it, the University of Utah suggests that for every pound lost during a run, you should drink 24 ounces of water. However, most of us can’t come home and chug 24 to 48 ounces of water immediately after running, so incorporate it throughout the day in addition to your normal water.

For those individuals who need electrolyte supplementation after a workout, reaching for a sports drink can be tempting, but watch out for high levels of sugar. Instead, look to diluted juice, coconut water, or electrolyte supplements like Nuun. Some athletes even reach for pickle juice – just make sure to dilute it a little to avoid an upset stomach.

Water is Boring: Alternative Options for Maintaining Hydration

Drinking an adequate amount of water every day can be, well, boring. Unless you live somewhere with particularly delicious water (here’s to you, Oregon), water can get old fast. While you still want the majority of your hydration to come from water, there are some alternatives you can mix in for variety.

Alternative Hydration

Mix these suggestions in with your regular water consumption and you’re sure to stay hydrated without getting bored. If you find other creative hydration methods, let us know!

Key Hydration Takeaways

Staying hydrated doesn’t have to be rocket science. Start with one of the baseline levels listed in the article and stick with for a few weeks, noting how you feel along the way. If you’re traveling, pay attention to elevation and humidity, as an increase in either of those will leave your body craving more fluids than normal. The same goes for any increase in training intensity or duration; keep your body fueled with as much water as it asks for and pay attention to your recovery. 

Happy training!

Hydration and Working Out: An Athlete’s Guide to Water, Electrolytes, and Optimum Performance

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