Triathlete Wearing Helmet And Sunglasses At Start Of Racing Drinking Electrolytes Out Of Water Bottle And Staying Hydrated

How to Make Sure You Start Your Race Hydrated

BY Andy Blow

Getting to the start line optimally hydrated means preloading your sodium levels smartly, not drinking every water bottle in sight.

When people talk about hydration, most of the time it’s about what and how much athletes should drink during exercise.

This is clearly important, but your performance is also massively influenced by how hydrated you are when you start exercising in the first place. Drinking a strong electrolyte drink to optimize your hydration status before long, hot, or really hard training sessions and events can significantly improve your performance.

At Precision Hydration we call this “preloading,” and the practice has been widely studied in the last 20 years or so, both with astronauts and athletes.

While there’s not a completely bulletproof consensus on the subject (there rarely is), there’s strong evidence that taking in additional sodium with fluids before you start sweating is effective in promoting increased acute fluid retention and in improving endurance performance — especially in the heat.

This article aims to give you a solid understanding of what you can do to arrive at the start of your next event optimally hydrated.

You’re Fighting a Losing Battle

Once you begin sweating, you start the battle against fluid and electrolyte loss, which is why starting off properly hydrated can be extremely beneficial. When you’re properly hydrated, you have a larger reservoir of fluid to draw from over time.

Starting well-hydrated has other benefits, too. Optimal hydration maximizes your blood volume, which helps general cardiovascular function and your ability to dissipate the heat produced by your working muscles. This reduces fatigue and enables you to maintain your performance for longer.

Despite the relatively obvious benefits of starting exercise well hydrated, a recent study of more than 400 amateur athletes showed that around 31% of them were turning up to training sessions (and, in some cases, competitions) dehydrated!

This data showed strong indications that this was very likely compromising their performance. This probably seems like common sense, especially if you’ve ever tried exercising when you know you’re a bit “dry.” Who in their right mind wants to start exercising hard in a dehydrated state if they’re trying to perform at their best?

This study certainly backs up previous work I’ve read on the subject and the kind of things we’ve seen over many years working with athletes. It’s not uncommon to see people start considering their hydration strategy once they turn up to a session or race, rather than preparing in advance.

Often this just happens because those of us who are not full-time athletes are running around between workouts and aren’t always able to think about preparing properly 100% of the time. That’s just life.

But it can also be a problem for full-time athletes when training two or more times a day, or at times when they’re just under a very high total training load. That’s because uncorrected dehydration from a prior training session can make its presence felt when the next session gets underway.

Overcompensating Impacts Performance

Although athletes turning up to training a bit low on fluids is relatively common, it’s generally less of an issue before major competitions. That’s not to say that turning up to an event dehydrated never happens, I’m sure it does.

But because most athletes care a lot about their performance in big events, there’s a tendency to increase fluid intake before the big day because extra priority is placed on all aspects of last-minute preparation.

The irony of this extra emphasis on pre-event hydration is that many athletes can go from slightly under-drinking before training to significantly over-drinking pre-competition. This can lead to a different set of problems including hyponatremia (low blood sodium levels caused by inadequately replacing the sodium lost when sweating and further dilution by drinking plain water or weak sports drinks), something that can be pretty catastrophic for health and performance if it goes unchecked.

A recent study found that 10% of athletes tested at the IRONMAN European Championships had hyponatremia, which shows you the extent to which hydration issues might be impacting performance.

What Can You Learn From Astronauts?

The importance of sodium in hydration and maintaining your performance was further proven by research conducted at NASA at the end of the 20th century.

NASA’s astronauts were commonly found to be suffering from low blood pressure because they were losing bodily fluids (and therefore blood volume) during their time in microgravity.

One NASA paper suggested that astronauts live with as much as a 3-4% deficit in total body fluid levels during a typical mission. It was causing them to feel weak, lightheaded and even to black out on re-entry or once they landed back on terra firma. That’s not something you want to be dealing with when you’re trying to land a rather expensive spacecraft!

To combat this, NASA tested lots of drinks containing different carbohydrates and electrolyte mixtures and found that the more sodium you put in a drink, the more effective the drink would retain in the body and bloodstream, thus correcting dehydration.

How to “Preload” Effectively

Preloading is all about striking a balance between being aggressive enough to drive some extra fluid retention in your bloodstream without leading to gastrointestinal issues or excessive fluid build-up (which might make you feel bloated and sluggish.

Typical sports drinks, which generally contain ~200 to 500 mg of sodium per liter, simply don’t cut it when it comes to preloading. They’re just way too dilute to make a meaningful difference to blood volume. They’re not vastly different from drinking water.

At the other extreme, most of the scientific studies that have been conducted in this area have looked at using extremely strong electrolyte drinks containing ~3,600mg of sodium per liter.

That’s like drinking a bag of saline solution that would normally be used in an IV! While this has been shown to be highly effective at boosting blood plasma volume, it has a tendency to cause upset stomachs, sickness, or diarrhea, something that is obviously very counterproductive when you’re trying to improve your performance.

At PH, we settled on a strength of 1,500mg of sodium per liter (32oz) for our preloading drinks. This seemed to be the “sweet spot,” making it very palatable and easy on the gut while still boosting your blood plasma volumes and getting you optimally hydrated before your start sweating.

If you want to test whether preloading improves your performance, follow these recommendations before your next long/intense training session or “B” race:

What To Do:

  • Drink a strong electrolyte drink (like PH 1500) with 500ml/16oz of water the evening before your activity.
  • Drink a strong electrolyte drink (like PH 1500) with 500ml/16oz of water about 90 minutes before you start. Finish your drink at least 45 minutes before you start to give your body time to fully absorb what it needs and pee out any excess.
  • Drink the strong electrolyte drink in water you’d have drank anyway to ensure you don’t overdo it.
  • DON’T just drink lots of water in the build-up to a race. You can end up diluting your body’s sodium levels before you start, increasing the risk of hyponatremia.

Why It Works:

  • Boosting your blood plasma volume before intense exercise is a proven way to enhance your performance, especially in hot conditions.
  • Having more blood makes it easier for your cardiovascular system to meet the competing demands of cooling you down and delivering oxygen to your muscles.
  • Stronger electrolyte drinks are very effective at increasing your plasma volume as they contain more sodium than a typical sports drink. That extra sodium helps to pull water into your bloodstream and keep it there.
  • Preloading may allow you to get away with drinking considerably less in shorter/harder events where previously they would have had to try to consume more on the move (not easy when you’re flat out!). It can also help reduce the amount of times you need to pee before you start.
  • You can’t preload anywhere near as effectively with weaker sports drinks as you’ll lose a large proportion of the fluid as urine. Or it’ll slosh around in your stomach without being properly absorbed.
  • Drinking a stronger electrolyte drink before you start can also help you avoid/alleviate muscle cramps, especially if you’re prone to suffering from them late on in events and especially when it’s hot. For more on why athletes suffer from cramps, read this.

If you’re looking for a way to optimize your performance then testing sodium preloading is definitely worth a try. If you have any questions about how to preload effectively or need help optimizing your approach, drop us an email.

Oh and if you decide you’d like to use our all-natural, multi-strength electrolytes to personalize your hydration strategy, just use the code TRAININGPEAKS to get 15 percent off your first order.


Blow, A. What is hyponatremia and how can you avoid it? Retrieved from

Greenleaf, J. et al. (1992, August 1). Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise. Retrieved from

Magee, P., Gallagher, A., and McCormack, J. (2017, April). High Prevalence of Dehydration and Inadequate Nutritional Knowledge Among University and Club Level Athletes. Retrieved from

Mozes, A. (2016, March 9). For ‘Ironman’ Athletes, Study Shows Danger of Too Much Water. Retrieved from

NASA. (2002, March 25). When Space Makes You Dizzy. Retrieved from

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About Andy Blow

Andy Blow has a few top 10 Ironman and 70.3 finishes and an Xterra World Age Group title to his name. He founded Precision Hydration to help athletes solve their hydration issues. He has a degree in Sport and Exercise Science and was once the Team Sports Scientist for Benetton and Renault F1 teams.

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