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Does Hydration Affect Performance

Does Hydration Affect Performance

When it comes to performance, there are many things that need to be considered and staying hydrated is one of them. Most people are aware of the benefits of hydration, like increasing brain performance and energy levels but it’s also a key factor in sports performance, especially as we edge closer to the warmer, summer months.  

Why Do We Need to Drink Water

Good hydration is fundamental for most aspects of life, not just exercise. In fact, regularly topping up your water levels ensures that all bodily functions can take place as usual. Without water, many of the important processes that occur inside your body cannot happen efficiently. 

The plasma in your blood, for example, is over 90% water and is vital for transporting glucose, electrolytes, vitamins, and minerals around the body to wherever they’re needed [1]. Water is also needed to help flush out waste products in the body via the kidneys, lubricates your joints, supports the digestive system, and contributes to youthful, glowing skin [2].  

Water is also central to your ability to regulate your body temperature. When you sweat because you are hot, your body is losing water through the skin to help cool you down, keeping your temperature regulated. In conditions where you sweat more, for example during exercise or hot weather, your body will lose more water to help keep you cool, so you’ll need to increase your water intake to replace what you lose through sweating. 

How Does Hydration Affect Performance?

It doesn’t matter what age you are, staying hydrated is important. Just a small drop in body water, just 1-2%, is enough to affect your cognitive performance [3]. So, not drinking enough water can have a detrimental effect on your ability to concentrate, learn, and think as well as affect your:

  • mood
  • motivation
  • reaction time
  • and ability to stay alert [3].

Dehydration affects your physical performance too. As your body loses water, your heart rate and body temperature will increase and, if you are exercising, you may feel like the exercise is becoming increasingly more difficult [4]. 

Because water is essential for supporting the normal function of the digestive system, if you are dehydrated, the amount of fluid that is absorbed from the intestines is reduced and this can cause symptoms, like:

  • feeling sick (nausea)
  • bloating
  • being sick (vomiting)
  • diarrhoea 
  • stomach cramps [4]

Dehydration and Athletic Performance

When it comes to your athletic performance, dehydration can significantly affect your cardiac output. That is the amount of blood your heart pumps out in one minute [5]. Not taking on enough water decreases your plasma volume, making your blood thicker and stickier, and lowers your central venous pressure, which contributes to less blood returning to the heart.

If these effects occur during exercise, it can mean less blood returns to the heart during diastole – when the heart relaxes and fills with blood. So, less blood is pumped back out during systole, causing a decrease in cardiac output. In other words, there is less blood available to working muscles.

Aerobic exercise performance has also been shown to be impacted by not replacing the water lost from the body or hypohydration. If you do not drink enough water during exercise to replace what is lost through sweat, then you are likely to experience hypohydration, and if you are in a warmer climate the effects can be even more exaggerated.  

That’s because hypohydration causes your body to store heat as you are likely to have a reduced sweating rate and reduced skin blood flow, contributing to an unregulated body temperature [6].

Symptoms of Dehydration

Thirst is an early sign that you may be dehydrated, so it’s not good enough to simply wait for the feelings of thirst to begin. A good way to monitor your hydration levels is to look at the colour of your pee. If it’s a pale straw colour, then it’s likely that you are well hydrated but if it’s darker in colour then this is a good sign you need more fluid.

Other symptoms of dehydration include:

  • dizziness or light-headedness
  • feeling tired
  • headaches
  • dry mouth, skin, or lips
  • peeing less than 4 times per day [7].

The best way to avoid dehydration is to get into the habit of drinking little and often. By constantly sipping on water you’ll help to replenish the water you lose naturally throughout the day through sweat, urine, tears, and other bodily processes.


It’s impossible to be healthy without hydration. Water is essential for most of the processes that occur within the human body and just a small loss can cause a decline in both cognitive and physical performance. 

You can help to prevent dehydration by regularly drinking small amounts of water throughout the day, to replenish what you’ve lost and keep your stores topped up. Drinking enough water is key to hydration and better performance.


[1] Informed Health. (2006). What Does Blood Do? Available at:,due%20to%20their%20red%20color.

[2] Hignett, J. (2019). The Importance of Hydration. BDA. 

[3] Riebl, S, K & Davy, B, M. (2013). The Hydration Equation: Update on Water Balance and Cognitive Performance. ACSMs Health Fit J: 17(6), pp 21-28

[4] Sports Dietitians Australia. (2009). Fluids in Sport. Available at: 

[5] Vincent, J-L. (2008). Understanding Cardiac Output. Crit Care.

[6] Sawka, N, A. (1992). Physiological Consequences of Hypohydration: Exercise Performance and Thermoregulation. Med Sci Sports Exerc 24(6), pp 657-70.

[7] National Health Service. (2019). Dehydration. Available at: