Pre-hydration for athletes

Pre-hydration for athletes
June 6, 2018 Marisa Michael

Hydration is a hot topic.

Everyone seems to want to know how to hydrate right. It gets confusing with so many products on the market. There are hydration powders, sports drinks, electrolyte tablets, salt tablets, coconut water, plain old water, and more. We have an amazing course on what product you should use, when to use it, and how much to drink!

Beyond which product you should use, there’s something else to consider.

Should you pre-hydrate? What is that? How do you do it?

If you have a big endurance event, such as an all-day tournament, marathon, or triathlon, you want to start out hydrated. It has great uses for firefighters and military personnel on long missions as well. These people depend on staying hydrated because their life depends on it (and yours might too!).

You may have seen the term “euhydrated.” Starting out euhydrated means you are adequately hydrated. You’ll set yourself up for better success. Having a smart hydration plan for the day will help you maintain performance.

What are some signs of dehydration?

Research shows that becoming dehydrated can lead to:

  • Decreased concentration
  • Increased rate of perceived exertion
  • Decreased sports performance
  • Dizziness
  • Thirst
  • Lightheadedness
  • Rapid heartbeat
  • Lethargy or sleepiness
  • Nausea/vomiting
  • Clinical dehydration can even be fatal!

What are signs and symptoms of over hydration?

On the flip side, becoming over-hydrated can be serious as well. This condition, known as hyponatremia, occurs when someonedrinks too much water, thereby diluting electrolytes (namely sodium). This is also a serious and potentially deadly condition that needs immediate medical attention.

Some signs and symptoms are:

  • Dark urine
  • Headache
  • Dizziness
  • Lethargy
  • Nausea/vomiting
  • Muscle weakness/cramps/spasms

Considering all this, an athlete that is in that sweet spot of happy hydration is an athlete that can perform their best. Enter pre-hydration.

How to pre-hydrate before an event

Pre-hydration is a strategic way to start well-hydrated before your event. You are adequately hydrated, but with an edge.

Here’s how you do it:¬†About 2-4 hours before you exercise, drink between 5-10 mL/kg of body weight.

How do you find that out?

Take your weight in pounds. Divide by 2.2. This is now your weight in kilograms.

Now take this number and multiply by 5 and then again by 10. This is the range in milliliters you need to drink over the next 2-4 hours.

If you want ounces instead of milliliters, divide by 30.

Here’s an example. Say you weigh 170 pounds. Divide by 2.2 =77.3 kg.

Take 77.3 kg and multiply by 5 and again by 10.

77.3 x 5= 386mL         77.3 x 10 = 773 mL

Divide milliliters by 30 to get ounces.

386mL/30 = 13 oz           773 mL/30 = 26 oz

So…for about 2-4 hours before your event, sip on 13-26 ounces of fluid to be pre-hydrated.

You can also do this for the day before a big race. Drink about 8 oz every hour. No need to drink so much that you are urinating super often or your pee is really clear. Just drink enough to feel hydrated and refreshed and ready to go hard!

There’s a lot more to hydration than pre-hydrating before a race. If you have other questions like:

  • How do I choose a sports drink?
  • How to I know when to use water vs. sports drink vs. electrolytes?
  • How do I stop cramping?
  • How do I stop runners trots?
  • How do I hydrate in special conditions, like altitude, humidity, cold, and heat?
  • What fluids “count” toward hydration?
  • How to I calculate my sweat rate?
  • How and why and when do I check urine specific gravity?

All this and more is covered in our Perfect Hydration for Athletes course! 


How to do pre-hydrate with glycerol?

Now, that’s a different question for another post. Head here to check it out.

Need more answers? No worries, we gotcha covered! Check out our hydration course for training and racing. You might also like our Endurance Fueling course!


Check out our amazing nutrition resources, including on-demand courses, free downloads, and webinar replays.

And be sure to follow us on Instagram!

Book an appointment with the dietitian

~This is general information only and not intended to be advice. Always check with your healthcare provider before undergoing any diet or lifestyle change. 


Some selected articles on pre-hydration:

Goulet EDB, Rousseau SF, Lamboley CRH, Plante GE, Dionne IJ. (2008). Pre-exercise hyper hydration delays dehydration and improves endurance capacity during 2h of cycling in a temperate climate. Journal of Physiological Anthropology, 27(5): 263-271.

van Rosendal SP, Coombes JS. (2013). Glycerol use in hyper hydration and rehydration: scientific update. Medicine Sport Sci, 59, p. 104-112.

Goulet EDB, De La Flore A, Savoie FA, Gosselin J. (2017). Salt + glycerol-induced hyperhydration enhances fluid retention more than salt- or glycerol-induced hyperhydration. International Journal of Sports Nutrition and Exercise Metabolism, DOI:10.1123/ijsnem.2017-0310

~Disclaimer: This is general nutrition information. Consult your doctor before changing any nutrition or fluid intake.