How to hydrate for endurance sports (the right way)

From the desk of
Robb Wolf
ScienceHow to hydrate for endurance sports (the right way)

Endurance sports place heavy demands on your body. When you exercise for hours on end, your hydration needs (including electrolyte needs) increase dramatically.

If you don’t account for this, not only will your performance suffer, but the hours and days following the activity will be rough, too. This is a typical complaint I hear from runners, cyclists, and swimmers alike.

Here’s what happens. Somewhere along that long-awaited marathon, triathlon, or Iron Man, they bonk. And after the race, they stay bonked for a long time.

If you look at the typical marathon course, you’ll find watering stations about every 2 miles. Water isn’t the problem; rather, it’s that the stations usually dispense sodium-free water. And water that doesn’t contain vital electrolytes—nutrients like sodium—doesn’t recharge your battery after losing a ton of salty sweat. Though it may seem counter-intuitive, adding water (without electrolytes) may make this situation worse.

It’s a common myth: folks think that as long as they’re drinking water, they’ll be hydrated. In actuality, that myth can be quite harmful—and even more-so than dehydration. Drinking water without replacing lost sodium dilutes blood sodium levels, and can cause a dangerous condition called hyponatremia.

The headaches, cramps, and confusion that come with exercise-associated hyponatremia plague a large portion of athletes. We’re talking anywhere from 10-70%, depending on the activity.

To make matters worse, exercise-associated hyponatremia is often confused with dehydration. This results in a dangerous and ineffective prescription: Drink more water.

Yes. Endurance athletes need to drink more water than most folks to replace the fluids lost through their sweat. But for the sake of their health, that water NEEDS to contain sodium. There are two factors at play here: 1) water, to provide the fluid volume to minimize stress on the cardiorespiratory system, improve evaporative cooling, etc., and 2) electrolytes, which are literally the “spark” that allow not just activity, but life.

That’s the short version. I’ll cover the clinical evidence more thoroughly in today’s article.

First, let’s cover the basics of hydration. This will set the stage for later, when we get into hydrating for endurance sports.

What Is Optimal Hydration?

There’s a fancy term for optimal hydration. It’s called euhydration.

According to a review paper from the journal Nutrients, euhydration is “the state of preserving body water within its optimal homeostatic range.”

Notice that the definition doesn’t say anything about drinking water. Hydration is a state of fluid balance in your body, not the act of pounding fluids.

A state of euhydration is essential for good health. About 50% to 70% of your body weight is water, and maintaining this balance of fluids keeps blood flowing through your veins, your brain sitting in cerebrospinal fluid, your body temperature constant, and much, much more.

Normally, your body does a nice job maintaining euhydration. If there’s too much water on board, you’ll pee it out. And if there isn’t enough, you’ll release hormones (like antidiuretic hormone) to retain it.

However, as we’ve covered, proper hydration isn’t just about water. Electrolytes are essential too—especially sodium.

Sodium is a positively charged mineral (called a cation) responsible for regulating extracellular fluid balance, or the water outside of your cells. When sodium levels aren’t optimal, your fluid levels aren’t optimally balanced, either. You’re sure to feel the effects if you don’t replace this nutrient, be it through headaches, reduced performance, or otherwise.

Top Two Hydration Problems for Endurance Athletes

When you’re exercising for long durations, you can easily slip into a state of suboptimal hydration. This suboptimal hydration takes two forms:

  1. Hypohydration (too little body water)
  2. Hyperhydration (too much body water)

I want to cover each separately, because both states can sap your energy, performance, and recovery.

#1: Hypohydration

Long-distance and high-intensity activities like running, cycling, and obstacle racing provoke tremendous sweat loss. If you’re slogging along in warm weather, you can lose anywhere from 4 to 10 liters of water!

As a result, total body water decreases significantly. If more than 2% of your total body water is depleted, you’ve likely entered the state of hypohydration. I say likely because some studies suggest elite runners may actually perform better with body-water levels that most medical professionals would consider “dehydrated.”

This “tactical” reduction in body water arguably improves the power/weight ratio for runners, allowing them to run further, faster. While this is certainly an interesting thought, a few things are still not clear.

For starters, how do these folks manage to use this technique without disrupting electrolyte balance? And is part of the reason that these athletes manage to compete at such a high level due to their ability to function at a modestly dehydrated state?

In short, I’m not exactly sure how solid of conclusions we can make from this information. At a minimum, we can argue the case that truly elite athletes are not necessarily avoiding dehydration at all costs. And, although speculative, I think it’s worth noting—not all of us are elite athletes, so we may not have the same leeway when it comes to hydration strategies.

Dehydration, in case you were wondering, is the process of losing those fluids. Hypohydration is the result.

When someone is hypohydrated, exercise tolerance decreases and performance suffers. This is well-documented, but the mechanisms behind why this happens are up for debate.

One potential reason? When you’re low on body water, your internal cooling mechanisms become less effective. Skin temperature increases, and your ability to sweat (and, therefore, cool down) decreases.

This is also why, at any given temperature, higher humidity makes exercise harder and more physically stressful. Even whilst well hydrated, high humidity reduces the effectiveness of evaporative cooling via sweat. To reinforce that last point, in one study, researchers found that when cyclists were hypohydrated, performance declined in lock step with rising skin temperature.

Should you just drink more water, then? Actually, water alone won’t cut it. Since sodium regulates fluid balance, adequate sodium intake is required to retain water and maintain the electrochemical gradient produced by higher concentrations of sodium outside cells and higher concentrations of potassium inside cells.

A 2003 consensus statement from the International Olympic Committee reads:

“Sufficient fluid should be consumed during exercise to limit dehydration to less than about 2% of body mass… Sodium should be included when sweat losses are high, especially if exercise lasts more than about 2 h.”

And if sodium isn’t included, you’ve got bigger problems to worry about than low body water.

#2: Hyperhydration

To prevent dehydration, many athletes guzzle sodium-free water beyond what thirst prompts. Since sodium is necessary for water retention (and electrochemical gradients), this isn’t a very well-thought out strategy.

To make matters worse, guzzling water creates a bigger problem: Hyperhydration.

Hyperhydration, also known as overwatering or water intoxication, is a potentially fatal state of electrolyte disturbance brought on by excessive water consumption.

You see this a lot in marathons. Runners drink electrolyte-free water on a set schedule, dilute blood sodium levels, then suffer the consequences of exercise-associated hyponatremia (low serum sodium).

In other words, hyperhydration = hyponatremia.

Hyponatremia is serious stuff. In the beginning, it causes headaches, cramps, confusion, and fatigue. As sodium levels continue to fall, seizures, brain damage, and even death can result.

More than a few elite athletes have perished from hyponatremia. What about dehydration? Not one sports-related death, in all the medical literature.

Fortunately, exercise-associated hyponatremia is fairly easy to prevent and reverse.

Getting Enough Sodium for Exercise

Sodium is an electrolyte that helps you transmit nerve impulses, regulate blood pressure, and maintain body water. It’s almost always found in nature as sodium chloride (NaCl), or salt.

If you’ve read this far, you know how important sodium is for hydration. It keeps body water at the Goldi-locks, “just right”, level. And when sodium levels fall to hyponatremic levels, the consequences are no joke.

Sodium needs go up in proportion to sweat loss. And the volume of sweat loss depends on the activity, ambient temperature, humidity, and a few other factors.

According to a paper from the Journal of Sports Sciences, vigorous exercise in warm climates can provoke sodium losses of 3.5 to 7 grams per day. For reference, that’s about 1.5 to 3 teaspoons of salt—in addition to baseline needs.

This sodium needs to be replaced. But how?

Simple: Drink salty water. A published example will help make my point.

In one randomized controlled trial, researchers rounded up 26 hyponatremic runners after a 161 km race, and gave them one of two interventions: IV sodium or a salty solution to drink. Both interventions restored their sodium levels.

The takeaway? Drink electrolyte water, but don’t wait until after the race to think about sodium. Consuming sodium before and during exercise can help maintain euhydration, and prevent problems from developing later on.

What Affects Hydration Needs During Exercise?

Different activities require different hydration strategies. A jog on a cool autumn day won’t require much planning. A 2-hour soccer match in 95 degrees and high humidity levels, however, will require frequent sodium and fluid replenishment.

Consider the following factors for exercise hydration:

  • Duration. If the activity takes longer than 2 hours, plan on drinking electrolyte water before, during and after. Depending on the below factors, shorter activities may require this strategy too.
  • Temperature / humidity. The hotter and more humid it is, the more water and sodium you’ll lose through sweat. Plan to replenish them accordingly.
  • Intensity. It’s easier to plan for longer runs, bike rides, and swims because the intensity stays relatively constant. Other aerobic sports, like soccer and jiu-jitsu, feature intense bursts at random intervals. When in doubt, over-prepare.
  • Availability of fluid. During a marathon, there are watering stations every couple miles, but is it electrolyte water? And how are you staying hydrated while training? Think on these things before you gallop out the door.

While we’re mainly talking about long distance runs, triathlons and the like—pause for a moment and consider how a sport like Brazilian Jiu Jitsu (wearing a gi and exerting at high output) could dramatically increase electrolyte needs.

We’ll end on some actionable advice to take with you.

Practical Tips for Exercise Hydration

To wrap up this article, I’ll give a few rapid-fire tips for endurance sports hydration. If you remember anything from this article, remember these:

#1: Drink to thirst

Thirst is a tightly regulated system. You don’t usually need to go beyond it. And when you do drink, remember to…

#2: Drink electrolyte water

You lose both sodium and water through sweat. If you only replace the water, your sodium levels will fall. Then you’ll feel and perform like garbage.

Two options here:

Remember, athletes can lose up to 7 grams of sodium per day while exercising in warm climates. You may need more than one stick on the sweatiest of days!

#3: Take potassium and magnesium

You lose very little potassium and magnesium through sweat. That’s why I didn’t focus on them today.

Nonetheless, if your diet isn’t rich in these electrolytes, your energy and exercise performance will notice. I recommend folks supplement 1000 mg potassium and 300 mg magnesium per day, in addition to dietary sources. Just to make that clear, “supplement” means just that, add to what we should be getting from a solid nutrition approach.

#4: Hydrate before, during, and after exercise

Don’t wait until the race is over to worry about hydration. Sip electrolyte water to thirst before and during exercise too. Your body will thank you.

Oh, and one last thing—have fun out there! That’s the whole point, isn’t it?

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