H2Outstanding: Regarding the Virtues of Water

Should you drink to thirst? Can you drink sports drinks instead? Let's find out!

Hey there, NPB athletes! Did you make time for a good, sweaty workout today? I hope so! Either way, you probably know that you lose electrolytes with all that perspiration. But here’s a little-known scientific fact: You also lose water! That’s right! Sweat is filled with water!

Okay, you caught me. That was sarcasm. I’m being an a-hole, but, in the words of Peter “Star-Lord” Quill, “I’m not 100% a dick.” I simply want to point out that, while everyone focuses on replenishing electrolytes, we often forget that we also need to replenish the stuff electrolytes float in: water.

Men are about 60% water. Women are about 55% water. This is because women hold more body fat than men and fat is hydrophobic. Some “experts” claim we are 70% water, but that’s the percentage of the earth’s surface covered by water. Two different things.

Water helps with all sorts of bodily processes. From an athlete’s perspective, here are some standouts.

• It helps you poop

• It aids digestion

• It regulates body temperature

• It maintains electrolyte balance

• It fuels exercise performance

I bet I had you runners and cyclists out there at “poop,” but I’ll discuss exercise performance anyway.

Science has known that dehydration impacts exercise performance since the 1940s. Even a 2% loss of body mass due to dehydration can have a negative impact. During events lasting longer than an hour, your heart, muscles, and brain all suffer when dehydrated.

A study in the journal Medicine & Science in Sports & Exercise showed fluid loss equaling 2% body weight appeared to reduce running performance by 5% at 1500m, 5,000m, and 10,000m—that’s like losing over a minute on your three-mile run time. Another study in the Journal of Applied Physiology showed that with 8% dehydration, participants walking to exhaustion lasted 55 minutes—as opposed to 121 minutes when hydrated.

It’s pretty logical if you think about it. Less water makes your blood thicker—and therefore your heart needs to work harder to move that blood around. Less water also means your core temperature goes up—and nothing works well when overheating.

Those negative impacts don’t go away off the playing field. A dehydrated body is a less effective body. Thus, it’s important to stay hydrated on the regular.

Can you drink too much water?

It’s hard to drink too much water. Endurance athletes sometimes do it during events, causing their sodium levels to go too low. This condition is called exercise-associated hyponatremia (EAH).

If you have an hour and you like scary stories, check out the “Epidemiology of EAH” section from the 2017 Frontiers in Medicine paper on the topic. It reads like the Wikipedia entry for a hyponatremia-themed season of Tales from the Crypt, featuring links to dozens of grisly over-hydrating mishaps, including this classic in which a Chi Tau frat pledge was made to stand on one foot and drink gallons of water until he passed out and died.

(I thought about making a Darwin Awards joke here but decided against it since I’m still working to reverse any residual a-hole stigma from a few paragraphs ago.)

A common theme in these instances is excessive consumption of water without replenishing electrolytes, thus explaining why sports drinks play an important role in prolonged physical activity.

It also inspires a very important tip. As is the case with almost anything you put in your mouth, do not consume all your daily water at once.

I was a little surprised by the conclusion of the paper: “Drinking according to the dictates of thirst, during and immediately following exercise will prevent the development of EAH when exercise is performed in temperate climates with duration of less than 17 h.”

They’re the doctors and all, but this advice seems naïve. Almost every legit endurance athlete I know has had issues with dehydration. None of them have ever said, “Gee, I was completely aware of my intense thirst, but I didn’t drink anyway—then blammo!” Sometimes, when you’re busting your butt, you shut out thirst and hunger signals along with all the other “please stop this madness” cues that your brain tosses at you. That’s why athletes put reminders on their bike computers or smart watches to drink and eat.

As an aside, I also wonder why they settled on 17 hours. What makes a 16-hour race easier?

A 2019 study in the journal Nutrients backs up my theory by showing that athletes doing six hours of treadmill running in a hot environment couldn’t tell if they were dehydrated.

Should you drink to thirst?

Even during those seven hours that you’re not exercising (assuming you’re doing Frontiers in Medicine’s breakthrough new workout, 17-Hour Abs), I still don’t think thirst is an ideal indicator.

By definition, thirst is “the body's defense mechanism to increase water consumption in response to a perceived water deficit.” In other words, by the time you’re thirsty, you’re low on water. You’re in a sub-optimal state.

Why on earth does it make sense to wait for that? Isn’t that’s like putting on sunscreen only after you’re sunburned? Ideally, proper nutrition keeps you in top shape as much as possible. If a little forward-thinking water consumption helps you avoid sub-optimality, I say drink!

Practical recommendations

While working out. There are a ton of solid recommendations out there. If you really want to dial it in, one thing you can do is take a sweat test.

• Weigh yourself before exercise

• Exercise without eating

• Track exactly how much water you consume during exercise

• Weigh yourself after exercise

• Subtract the amount of water you consumed from the difference

Doing this in a variety of circumstances (various weather conditions and exercise intensities) should give you a reasonable idea of how much you sweat.

Another option is to invest in sweat-measuring technology like a Nix Biosensor, which is a good way to take the guesswork out of it. And nobody likes guesswork.

Just keep in mind that you don’t absorb all the water you drink, so it’s always a good idea to drink more than you sweat, although adding electrolytes and sugar to water does improve absorbency, which is another good reason to use the sports drink of your choice during long efforts.

Or, if all this fancy testing stresses you out, the American Council on Exercise suggests:

• 17 to 20 ounces of water two hours before the start of exercise.

• 7 to 10 ounces of fluid every 10 to 20 minutes during exercise.

• 16 to 24 ounces of fluid for every pound of body weight lost after exercise.

During your day. Again, you can find recommendations up the hoo-hah, but I don’t think there’s a universal number. Even the CDC is vague about it. It’s a question of experimenting and finding what works for you.

Personally, I drink about an 8-ounce glass of water first thing in the morning. After that, I fill a 40-ounce Hydro Flask with water and make a point of drinking over the day—in addition to whatever I drink while exercising. If I had a long, sweaty workout, I might drink a couple Hydro Flasks. The rest of my water tends to come from the foods I eat. Since I consume a lot of fresh produce, it’s a pretty hydrating diet.

There’s often a little coffee and beer floating around in the mix, but I don’t factor those in. There’s no shortage of research confirming both hydrate you, but I like to walk my talk, so I stick to H2O.

Sports drinks all day?

If you’re still ruminating on the fact that your body better absorbs fluids in sports drinks, I wouldn’t recommend making that a habit when not working out. All the extra added sugars won’t do you any favors. Also, it gets a bit pricey.

An exception might be when you’re seriously depleted, like when you’re sick or after a crazy, very long run or ride in hot weather—or when you’re hungover, not that I’d know about this firsthand. For example, I never spent a long weekend back in 2016 in New Orleans with two hard-partying Australians, surviving only thanks to willpower, po-boys, and electrolytes.

But when you’re not rocking the French Quarter with the lads from Down Under, just stick to plain water. Trust this a-hole. It’s good for you.