How Much Water Runners Really Need

By Nike Running

How Much Water Runners Really Need
How Much Water Runners Really Need

Getting the right amount of fluids is just as important to your training as distance, speed and fuel.

Getting the right hydration can help transform your performance. Learn why even mild dehydration can derail a run, and exactly how much you should drink before, during and after a workout.

Getting enough to drink on a run may seem simple. Just don't get too thirsty, right? But there's more to it than you may think. Here's why hydration matters so much to your performance and how to make sure you're properly topped up.

How You Lose Fluid

When you run, you lose fluid through sweating and breathing—significantly more through the former. "Heat is a major by-product of your working muscles", says Monique Ryan, RDN, a sports nutritionist with more than 25 years of experience advising professional and endurance athletes and teams. "The more heat they generate, the more your body temperature rises, and the more you'll sweat".

"When fluid losses through sweat are not replaced, your body temperature rises further and exercise becomes harder".

Sports Nutritionist Monique Ryan

That sweat is the most important way your body cools itself, explains Ryan; the evaporation of the liquid is what cools your skin (a reason to not wipe sweat away). "When fluid losses through sweat are not replaced, your body temperature rises further and exercise becomes harder".

Inside your body, sweating causes the blood volume to your muscles to decrease, says Ryan. That's because a significant amount of blood flow is redirected from the working muscles to the skin to aid the process of sweating. And with less blood flow, your muscular endurance is impaired, she says. Plus, your heart has to work harder to pump the remaining blood, which can stress your cardiovascular system and jack up your heart rate. Translation: Suddenly your 5-miler feels a lot harder than it should.

"To maximise your performance, your goal is to always be hydrated".

Precision Nutrition Director of Nutrition Brian St. Pierre

How Much Water Runners Really Need

As the temperature and humidity rise, this process is exacerbated. Even on a 10°C day, you may start to sweat more. And with just 40 percent humidity, sweat doesn't evaporate as well from your skin, interfering with your natural cooling, says Ian Klein, a specialist in exercise physiology, cross-training and injury prevention at Ohio University.

The solution: "To maximise your performance, your goal is to always be hydrated", says Brian St. Pierre, RD, the director of nutrition for Precision Nutrition.

The Signs of Dehydration

The funny thing about hydration is that when you're doing it right, you don't even notice—running feels normal. Dehydration feels like the opposite of that.

"As your fluid levels go down, your body stops functioning optimally", says Ryan. "You start to overheat. This affects your concentration and focus, your heart rate rises and exercise seems harder".

The longer you go without replenishing your fluids, the more severe the symptoms can get. If you notice that your breathing is laboured, your pulse is fast and/or you're dizzy, fatigued and even confused, these may be signs of heat stroke. You never want to get to this point. Heatstroke is an emergency situation and can cause permanent damage to your brain, heart and internal organs.

What Dehydration Does to Your Running

You may think being thirsty on a run or during a race is merely annoying. But it can have a real impact on how fast you move and how good you feel.

When the amount of water in your body changes, it can also mess with your body's levels of electrolytes and essential minerals.

Research has shown that when you lose more than 2 percent of your body weight to dehydration, it can lead to a reduction in endurance performance. (Think there's no way you'd ever get that dehydrated? Here's the quick maths: If you weigh 68kg, that means losing 1.3kg of water weight. This can easily happen during a hot day and/or during a hard run.) Other research shows that dehydration can result in a higher rate of perceived exertion. The outcome makes sense—if exercise feels harder, your performance will likely suffer. In fact, 70 percent of runners experienced one or more incidents in which they believed dehydration resulted in a major decrease in their performance, research published in the Journal of Athletic Training found.

When the amount of water in your body changes, it can also mess with your body's levels of electrolytes and essential minerals including sodium, potassium, calcium, chloride and magnesium. "You need these electrolytes for your muscles to function properly", says Ryan. They move nutrients into your cells, move waste out of your cells and help regulate nerve function and muscle function, including your heart. All of which is, well, crucial for performance.

How Much Water Runners Really Need

So, What's the Ideal Amount to Drink?

While the effects of running on far too little water are extreme, you shouldn't have to stress about your intake. The majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide, according to a report from the Institute of Medicine of the National Academies.

That said, if you operate best with a specific goal, here are some stats: The report found that women who were adequately hydrated consumed approx. 2.7 litres of water from all drinks and foods each day, and men averaged approx. 3.7 litres. About 80 percent of that intake came from water and other beverages, and the other 20 percent came from water-rich foods (fruits and vegetables are an especially good source).

"If you're training for longer than an hour, you should be drinking anywhere from approx. 710ml to 946ml per hour of your run".

Precision Nutrition Head Performance Nutrition Coach Ryan Maciel

Of course, these numbers are based on the average American. If you're a highly active runner, you likely sweat more, which means you have more fluids to replace.

The idea is to replace that sweat as you lose it. "If you're training for longer than an hour, you should be drinking anywhere from approx. 710ml to 946ml per hour of your run", says Ryan Maciel, RD, the head performance-nutrition coach at Precision Nutrition. That's about 237ml every 15 to 20 minutes. You want to sip, not chug. Aside from taking in too much water, gulping can also cause GI distress, Maciel says.

Make sure to rehydrate when you finish your workout too. One easy way to gauge how much to drink is to weigh yourself before and after you've trained for an hour or more, says Maciel. "If you lose 450g, then you should replace that with about 473ml of fluid", he says. If you lose more, drink more during the hours after your run—and don't forget to account for any fluid you took in during the run, he says.

In general, the most straightforward way to monitor your hydration status is to look at the colour of your urine, says Maciel. "If it's dark, you need to drink more; if it's pale yellow to clear, you're pretty well hydrated".

Tips for Carrying H2O

Relying on public water fountains to stay hydrated during your workout is tough, and for some routes, impossible. Gripping a water bottle throughout your run can be a drag too. A few good solutions: handheld bottles that fit into a carrier with a band that slides over your hand; bottle belts, which put the weight of the water on your hips; and vests that let you stash bottles on your chest or have bladders with straws on the back.

Keep in mind that while this gear tends to be ergonomic, it can have an effect on your form, says Jason Fitzgerald, a USA Track & Field–certified coach, head coach of Strength Running and the host of the Strength Running Podcast. "A full hydration bladder can cause you to lean too far forwards, and wearing a water bottle on one side of your hip or carrying it in one hand can make you lean slightly more to one side", he says.

While neither are a huge deal—and certainly less problematic than being dehydrated is—these little imbalances can add up over time. Try your best to even them out by switching the hand that's holding the bottle, the side that the bottle is stashed on in your belt, or if a belt has multiple bottles, taking sips from each one instead of downing one at a time. As for hydration bladders, fill them with only as much water as you need for your workout, not necessarily to the brim.

How Much Water Runners Really Need

When to Consider Electrolyte Supplements

Running for less than two hours? Hydrate with water, recommends Maciel. If you're going to be out on the road or trail longer than that, or if it's particularly hot and you're sweating a lot, you need to replace your lost electrolytes—the minerals that keep your body humming—along the way, he says.

To get those electrolytes, some runners like to sip sports drinks, while others prefer gels or chews. There isn't a best or better method, so experiment with a few different products to see what works for you. Just remember that more isn't more when it comes to these supplements. You don't want to chase a sports drink with a handful of electrolyte chews. Like everything, when it comes to hydration and nutrition, you want a balance.

What to Do in a Race

To get the most out of your training, you should be hydrating well all the time, and particularly in the weeks leading up to your event, says Maciel. "Chugging water the night before a race is not going to make up for not hydrating enough all those other days", he says. In other words, if you trained while slightly dehydrated, you just won't have the fitness you could have had if you'd taken in more fluids.

To get the most out of your training, you should be hydrating well all the time.

How much you'll need to drink along the course depends on the length of the race. If you'll be running for less than an hour—say, a 5K—you likely won't need to hydrate during the run. For anything longer, fall back on your hydration protocol for long runs (aiming to sip approx. 710ml to 946ml each hour), says Maciel.

Races typically have hydration stations along the course so you don't have to stress about carrying fluid with you, and most offer water and a sports drink. Look at the course map ahead of time to see how far apart those stations are and whether the event separates them by miles or kilometres (5 miles apart is a lot further than 5K!), then plan your hydration strategy accordingly. Finally, make sure you know what the event is serving, and road-test the specific sports drink in training so, come race day, you know it agrees with your gut.

How Much Water Runners Really Need

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How Much Water Runners Really Need

Nike Run Club

Your perfect running partner.