top of page

Hydration and Exercise Performance

Updated: Mar 30

A necessary component of fuelling well is hydrating well. Because this is important for athletic performance, this article will get you familiar with the science behind hydration best practices, and give some practical tips to achieve them.

So far, we have written a number of blogs on how to fuel correctly, namely, how much food (carbohydrates) to eat pre-, during, and post-exercise. In this blog, we will delve into the science of hydration. The term hydration refers to the process of replacing the lost fluid, particularly water, in something. Intuitively, dehydration is the opposite, and occurs when water is removed from something, or when there is an inadequate supply of water. It follows that the hydration status of the body is determined by the balance between water intake and water loss. Now that we have defined the terms, let’s chat about hydration and performance.

Why we Must Hydrate

When we exercise, our body temperature rises. To ensure that our body doesn’t overheat, we sweat. As the intensity of exercise heightens, and if it is performed in hot conditions, the rate of sweat will be accelerated. Because sweat is made up of water and electrolytes, it’s vital to replace these nutrients via fluids and/or food.

Performance Effects of Hydrating During Exercise

The literature is consistent in reporting improved exercise performance when individuals are given fluids during exercise. But, oftentimes the fluids contain a mixture of carbohydrate, water, and electrolytes, which makes it difficult to explore the independent effects of each. As we have discussed before, consuming carbohydrates during exercise improves performance when compared to not doing so. But, there’s evidence to suggest that the effects of carbohydrates and fluids are independent but additive, meaning they can both contribute to improved performance, and when consumed together it’s a win-win scenario.

In one study, male and female runners lasted approximately 25 minutes longer during a test to exhaustion when drinking ~190 ml of water just before exercise, and ~125 ml every 15 minutes during, compared to when they consumed no fluids (1). In another study, male athletes experienced a 6% improvement in sprint performance at the end of a 50-minute cycle, when they consumed ~1.3 litres of water throughout vs. just 200 ml (2). To highlight the further benefit of consuming carbohydrates with fluids during exercise, when participants consumed 1.3 litres of a carbohydrate-containing sports drink throughout, they experienced a 12% improvement in performance compared to just 200 ml of water.

Avoiding Dehydration and Overhydration

Naturally, dehydration is expected to decrease performance, and research backs this up. It is estimated that body mass losses (due to sweat) of 2% can negatively impact performance, and losses of 5% may decrease time-to-exhaustion performance by ~30% (3). However, caution is advised in interpreting these results for the following reasons. Firstly, time-to-exhaustion performance does not necessarily equate to sports performance. Using football as an example, the stop-and-start nature of the game is not exactly comparable. In addition, studies which include participants who start exercise in a euhydrated (well-hydrated) state, and then develop dehydration, have been less consistent in reporting poorer exercise performance (4). So, what we can say is that yes, dehydration likely negatively impacts performance, but by how much? That’s up for debate.

On the other end of the spectrum, overhydration can negatively impact performance. In fact, severe overhydration, or hyponatremia (water intoxication), is potentially lethal. This occurs when excess water, relative to sodium, accumulates in the blood and is defined by abnormally low amounts of sodium in the blood (5). While this is very rare for footballers, those doing very long-duration exercise, e.g., marathons or ultramarathons, can develop this condition as a result of consuming an excessive amount of low-sodium fluids during exercise. This is where electrolytes can help, and for those doing such exercise types, ensuring you replace lost electrolytes (in sweat) is crucial. If your body weight increases after a bout of exercise, this is a sign of hyponatremia, and you should go to your nearest hospital’s A & E (emergency department) immediately.

Tips for Hydrating Optimally

Now that you understand the importance of maintaining a well-hydrated state when exercising, here are some tips to help you hydrate optimally (5):

  • 24 hours before exercise: drink generous amounts of fluids; monitor the colour of your urine (should be a pale yellow)

  • 2–4 hours before exercise: drink 5–10 ml/kg of fluids—this allows enough time for excess fluid to be excreted before starting exercise

  • If you’re a 70 kg individual, this works out to 350–700 ml

  • 5–10 minutes before exercise: if possible, drink 150–350 ml of fluids

  • During exercise: if possible, drink small amounts of fluids every 15–20 minutes

  • After exercise: drink up to 1.5 litres for every kg of body mass lost; including sodium and potassium can lead to better fluid retention (often you’ll get enough of these from the foods in your post-exercise meal)

  • Sipping drinks slowly rather than gulping may prevent swallowing excessive air (which is thought to contribute to nausea)

Final Thoughts

Nailing your hydration strategy can set the scene for optimal performance, but as with a number of things in nutrition, recommendations and best practices may vary from individual to individual. So, give these tips a go, see how you feel and perform, and adjust accordingly!

As always, feel free to reach out to us, here: [email protected], for any enquiries about football, or for further information related to the information in this article.

Have a nice weekend!

Patrick Elliott, BSc, MPH

Health and Nutrition Science Communication Officer at Training121

Founder of Just Health IG:

Health Disclaimer: this article is for informational and educational purposes only, and is not a substitute for professional advice. For health advice, speak to a physician or other qualified health-care professional, and for nutrition advice, speak to a qualified nutrition professional (e.g., registered dietitian). The use of information on this app/site is solely at your own risk.


(1) Fallowfield JL, Williams C, Booth J, Choo BH, Growns S. Effect of water ingestion on endurance capacity during prolonged running. J Sports Sci. 1996;14(6):497-502. Available at:

(2) Below PR, Mora-Rodríguez R, González-Alonso J, Coyle EF. Fluid and carbohydrate ingestion independently improve performance during 1 h of intense exercise. Med Sci Sports Exerc. 1995;27(2):200-210. Available at:

(3) Maughan RJ. Fluid and electrolyte loss and replacement in exercise. J Sports Sci. 1991;9 Spec No:117-42. Available at:

(4) Goulet ED. Effect of exercise-induced dehydration on time-trial exercise performance: a meta-analysis. Br J Sports Med. 2011;45(14):1149-56. Available at:

(5) Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501-28. Available at:

Technical Terms

Electrolytes: Minerals that carry an electrical charge when dissolved in water, e.g., sodium, potassium, etc. When we sweat, we lose electrolytes, and must replace them via fluids or food. Electrolyte losses are not of huge concern in lower intensity exercise, but become more important the longer and more intense the exercise, and especially in hot conditions.

Dehydration: Occurs when water is removed from something, or when there is an inadequate supply of water.

Hydration: The process of replacing the lost fluid, particularly water, in something

Hydration status: How hydrated something is; is determined by the balance between water intake and water loss.

Euhydrated: The state of being well hydrated.

Overhydration: Also called water excess or water intoxication, is a condition in which the body contains too much water.

Hyponatremia: When excess water, relative to sodium, accumulates in the blood and is defined by an abnormally low concentration of plasma sodium (<135 mmol/l).

102 views0 comments

Recent Posts

See All
bottom of page