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Hydration for Runners: Everything you need to know!

Stay hydrated to stay safe and perform at your best.

Proper hydration plays a crucial role in our daily lives and sports performance. Improper hydration can lead to dehydration or hyponatremia, resulting in dizziness, fatigue, and poor running performance.

On shorter runs—say anything less than 5 miles or 8 kilometers—hydration shouldn’t be a huge issue. If you’re out for 30-45 minutes, it’s fine to replenish your fluids after you finish unless you are running in the heat.

Once you start running longer distances, you have to be mindful of your hydration levels. If I go out for anything over a 45-minute run, I’ll drink water while I’m running.  

There are instances where runners actually drink too much water, rather than not enough. Drinking too much can lead to stomach slosh or, much worse, hyponatremia if you completely mess up your electrolyte balance.  

Likewise, dehydration during a run can lead to a headache after running and medical issues, and certainly doesn’t do your kidneys any good.  

In this hydration for runners guide, we provide everything you need to craft your own hydration plan for your running workouts and races.

Hydration for Runners: Everything you need to know! 1

How Much Water Should Runners Drink Daily?

How much fluid you need for adequate hydration is two-fold:

  1. How much fluid do you need daily if you’re active?
  2. How much fluid do you need to consume during your workouts and races?

Your daily hydration status is key to successful workouts and races as you don’t want to start your workouts in a hydration deficit. Always start your workouts fully hydrated.

General Baseline Hydration

In general, the recommended 8-10 cups of water a day is a good baseline. Then, you can adjust from there.

If you are very active and do a lot of high-intensity exercise, or if you live in a hot or humid climate and sweat a lot, you’ll need to increase your daily hydration.

Daily hydration also includes other liquids you drink, such as milk, juice, coffee, tea, etc. so you’re not just limited to plain water to meet your hydration needs.

Prehydrating Between Intense Workouts and Races

If it’s been less than 12 hours between intense workouts or races, you’ll want to pre-hydrate about 4 hours prior.

For pre-hydration, slowly consume 5-7 ml (0.17-0.23 oz) of fluid per 1 kg (2.2 lb) body weight.

This is roughly the equivalent of a large glass of water for a 75kg average person.

If you are concerned about hydration during your workout or event, you can add some sodium-containing snacks or fluids with your pre-hydration routine to help with water retention.

Pre-hydration isn’t always necessary if there have been over 12 hours between workouts or you are already well hydrated. But it never hurts to keep tabs on your hydration levels before your running workout or race!

hydration for runners

How Much Should You Drink During Exercise?

The goal of hydrating during running is to prevent dehydration which would negatively impact performance. Having said that, some small level of dehydration is normal during prolonged workouts; you can re-hydrate well after your run.

With this in mind, the current research for performing activities where you sweat is to drink when you begin to feel thirsty. However, there is also contrasting thoughts that when you are thirsty, it’s already a bit too late.  

This has also been described as ‘drinking a sufficient amount to prevent thirst’ in the study that concerned it.1Goulet, E. D. B., & Hoffman, M. D. (2019). Impact of Ad Libitum Versus Programmed Drinking on Endurance Performance: A Systematic Review with Meta-Analysis. Sports Medicine49(2), 221–232. https://doi.org/10.1007/s40279-018-01051-z

Running and Hydration – Here’s The Rule of Thumb

If you’re looking for an actual quantity of water so you can plan your hydration needs in advance, here’s the average consumption:

In general, it’s recommended that athletes aim to drink 0.4-0.8 liters per hour (L/h) or 8-16 ounces per hour (oz/h). To get even more precise, you can calculate your sweat rate.

How To Calculate Your Sweat Rate

Your sweat rate is highly individual, so calculating your own sweat rate and fluid loss during running workouts or races to customize to your own needs is a great way to ensure proper fluid consumption.

Hydration for runners: everything you need to know

Sweat Test

1. Weigh yourself with no clothes.
2. Run for one hour at your specific race pace.

Note: During your run, do not consume or expel any liquid…so in simpler terms: no drinking or peeing! This will throw off your calculation.

3. After your one-hour run, take off your shoes and clothes, and if necessary, wring out your sopping wet hair.
4. Weigh yourself again.

Now let’s calculate our results!

Take your pre-run weight and subtract your post-run weight. The outcome will be the amount you sweat per hour while you run. Let’s take a look at examples:

Kilos: 
50 kilos (pre-run weight) – 48.5 kilos (post-run weight) = 1.5 kilos = 1.5 liters per hour

Pounds:
125 pounds (pre-run weight) – 122 pounds (post-run weight) = 3 pounds = 48 ounces per hour

If you are calculating this for race day, try to replicate conditions so you can estimate your fluid needs for the temperature and humidity you’ll likely experience.

How Often Should I Drink Water When Running?

It’s important to remember that some dehydration is normal during prolonged exercise, and attempting to replace your exact fluid quantity during exercise can be counter-productive and lead to stomach slosh: follow the sip rule and rehydrate the rest when you cross the finish line.

This means sipping your fluids instead of chugging them down. You want a constant flow of hydration instead of consuming it in large quantities all at once.

You can set alarms on your running watch for every 10 minutes or whatever time interval feels right for you and take a sip. This way, you won’t forget.

The goal is to weigh the same after your workouts since any rapid weight loss is attributed to water and to prevent dehydration, you want a 1:1 replacement of fluid lost (including fluids you’ve consumed after your workout).

Once you’re done with your running workout, your goal is to replace any lost fluids from your workout (as well as electrolytes if needed), and then move into your regular daily hydration maintenance.

Hydration for Runners: Everything you need to know! 2

What are electrolytes?

When your sweat rate begins to increase, you’ll want to start adding essential minerals (called electrolytes) to your hydration routine and fluid intake to replace lost minerals in sweat loss.

You know how sweat is salty? It’s because you’re excreting these minerals.

Electrolytes are minerals considered essential for proper functioning of the human body and they are often lost through sweat.

Electrolyte minerals exist as charged ions and include sodium, calcium, magnesium, and potassium (some lists include chloride and phosphorus as well).

These minerals are essential for cellular function and help to regulate pH in the body, and they are essential for nerve and muscle function (including the heart muscle).

With increased sweat rate, there is an increase in loss of these minerals. There are several factors that influence sweat rate:

  • Workout intensity
  • Humidity (people sweat more in high humidity)
  • Heat
  • Genetics
  • Sex (men in general tend to sweat more than women, although this is not always the case)
hydration for runners

The amount of sweat people lose during workouts can be highly individual, as well as the mineral makeup of their sweat.

Some people’s sodium levels dip lower than others when they sweat, so it’s important to learn more about your body’s individual sweat rate

If you know that you’re going to be doing a race or event in a hot and/or humid climate that you’re not used to, take some time to acclimate yourself beforehand to not only perform better, but also to help your body adjust to new hydration needs.

bottle of gatorade next to a pond

Hydration options for runners

There are many different hydration options available to runners and fitness enthusiasts, and sometimes the number of options can be overwhelming!

But we’re going to break down the main types of hydration products available and what products are best for you and your fitness needs.

When Does Just Pain Water Do The Trick?

Plain water is the best thing to start with for regular daily hydration. For most people and recreational exercisers, plain water will suffice for hydration if your workouts are:

1) Moderate in intensity
2) Last less than 1 hour
3) Are in cool temperatures and low humidity.

But once you start to increase your workout length, workout intensity, ambient temperature, or humidity, your hydration needs change based on an increased sweat rate and greater loss of electrolytes and minerals through your sweat.

When any (or all) of these factors change and your sweat rate increases, you’ll need to start adding electrolytes to your hydration regimen to replace lost minerals since plain water alone won’t be enough.

When Should You Add Electrolytes?

Once you start to sweat more due to higher temperatures, and more intense and longer workouts, you’ll need to switch from plain water to a sports drink that includes electrolytes to replace minerals lost during heavy sweating.

Electrolytes come in several different forms for you to choose from:

  • Pre-mixed drinks
  • Powders or tablets you mix with plain water
  • Capsules you swallow as a supplement
  • Chewable tablets (like Salt Stick fast chews)
  • Electrolytes mixed into energy chews and gels

The type of electrolyte you choose will depend on your workout, your palate, your fueling needs, and how you plan to carry your hydration during your workouts.

Also, every brand of electrolyte replacement has a different formulation. So some brands will have more sodium, others will have more potassium, and still others (like Ultima) will have trace minerals like selenium and copper (I’ve found my body really likes these ones!).

Try out and research a variety of different brands to see which ones work the best for your body.

Most electrolyte powders are sugar-free, so if your workouts aren’t long or you plan on having a separate fueling plan with carbohydrate chews, gels, or actual food, then the sugar-free electrolyte drink mixes will work well for you.

If your workouts are going to be long and you will be able to refill a water bottle, it’s great to keep electrolyte drink mix packets or tablets (like Nuun) with you to add to water at your convenience.

If your workout isn’t going to be long, but you need electrolytes because it’s hot or you’re a heavy sweater, then you can take a small bottle of pre-mixed electrolytes with you or a few electrolyte chewables if you’re not taking very much liquid with you on your run.

It’s important to note that while you may like the idea of a chewable tablet or capsule, if you’re doing a race, you might not be able to stomach a chewable or be able to easily swallow a capsule.

Make sure to always train with your planned hydration methods before racing! Don’t try new electrolyte or hydration methods during a race that you haven’t tried beforehand during training sessions.

Remember: this all takes practice to figure out an electrolyte replenishment strategy that will work for you! Have some fun trying out some new methods and brands during your training runs to see what works best.

Related: How Frequently Should You Take Energy Gels During Races?

Sports drinks that contain carbohydrates and sugar

Sports drinks that contain calories and sugars typically aren’t necessary for regular intensity workouts that are under 1-1/2 hours, so it’s okay to skip these during and after your regular workouts.

But they are helpful for adding easily digested calories if you are doing endurance running where you need a carbohydrate fueling strategy.

A sports drink that has different kinds of sugars (like glucose and fructose) along with electrolytes is very helpful in this case and is a great thing to have on hand for quick fueling.

Just like with electrolyte powders, not every carbohydrate sports drink is made the same, so look into different brands to see what works for you.

Certain types of sugars do not agree with some people (like people with IBS have a difficult time digesting fructose), so look for sports drinks with sugars that you can tolerate during heavy exercise.

Sports drinks are an easy way to consume calories for your fueling strategy during endurance running since some runners cannot stomach solid food (or even gels or chews) during an endurance race.

Make sure to plan ahead and count your sports drinks, gels, chews, and/or food into your entire fueling plan.

If you overdo it with the carbohydrate fueling all at once, you may end up with an upset stomach as your body tries to handle multiple concentrated carb sources while you’re exercising.

Risks of poor hydration

Making sure that you pay attention to your hydration is not only important for optimal athletic performance, but it’s crucial to your health and wellbeing!

Dehydration

Most people aren’t going to get dehydrated to the point of serious health consequences or death, but many people do experience signs of dehydration like lethargy, muscle cramping, dizziness, confusion, dark urine color, high heart rate, increased body temperature, etc.

Mild dehydration (1%-2% loss of body weight during exercise) is normal during exercise, especially during endurance events like marathons.

But your goal should be to manage mild dehydration and keep it from becoming severe dehydration that can result in serious complications like seizures.

What Are The Signs Of Dehydration In Runners?

Other symptoms of dehydration include:

  • lightheadedness
  • thirst
  • fatigue and lack of energy / enthusiasm
  • lack of need to use the bathroom
  • dry mouth
  • constipation

Can Overhydration Be A Concern For Runners?

Hyponatremia

One aspect of hydration that people don’t often address is hyponatremia, which is over hydrating (the opposite of dehydration).

Hyponatremia is defined as an abnormally low concentration of blood sodium and it can occur when someone drinks too much low-sodium fluids over long periods of time compared to their sweat rate.

The greatest predictor of hyponatremia is an increase in weight during the duration of a workout, meaning you have consumed an excess of fluids.

Runners who are exercising at low to moderate intensity for long periods of time and who have a low body mass index are more susceptible to hyponatremia, while high intensity exercisers are more likely to suffer from dehydration.

To prevent this, make sure that you are consuming moderate amounts of liquids for your needs during exercise, and you are also including sodium and electrolytes in your hydration routine when you’re running for longer periods (over 1-2 hours)

How to hydrate during your run (and how to calculate how much water you need) - Marathon Handbook

How Can I Prevent Dehydration While Running?

Once you’ve figured out how you want to stay hydrated for your training runs and races, the next task is figuring out how you can stay hydrated during your runs.

Here are some hydration tips so you can plan for your running workouts or races:

  • Plan out your route to go by places with water (like drinking fountains). If you need to do a longer run but can’t carry water with you, create loop routes where you can come back to a water bottle regularly.
  • Check out running vests, running belts, and handheld bottles to take with you so you never lack the necessary amount of fluid you need to stay hydrated.
  • Ensure you are hydrated on a daily basis to support not only your running, but overall health.

For more information on electrolytes, check out this next guide:

References

  • 1
    Goulet, E. D. B., & Hoffman, M. D. (2019). Impact of Ad Libitum Versus Programmed Drinking on Endurance Performance: A Systematic Review with Meta-Analysis. Sports Medicine49(2), 221–232. https://doi.org/10.1007/s40279-018-01051-z
Photo of author
Sarah Jane Parker is a food and healthy living blogger at The Fit Cookie, an ACSM Certified Personal Trainer, ACE Certified Health Coach, Revolution Running certified running coach, YogaFit Level 1 certified yoga instructor, and an ACE Certified Fitness Nutrition Specialist.

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