The impact of dehydration on performance

Of all an athlete’s concerns, hydration is often the most neglected; and yet, it is undoubtedly one of the most decisive factors in athletic performance: dehydration can seriously harm performance and, above all, health.

The subject is crucial, yet even some experienced athletes tend to neglect it. This may explain the sudden fatigue felt halfway through a race. Keep in mind that if you lose even 1% of your body weight through sweat during exercise, your performance already decreases by an average of 2%.

Dehydration and hyponatremia

So why is hydration so important during exercise? It is quite simple: water is essential for ensuring the proper, rapid, and easy circulation of blood, which itself transports oxygen and sodium to our muscles and enables each of our limbs to function efficiently. When you are dehydrated, your blood becomes thicker and therefore circulates less easily: your heart has to pump harder. Drinking regularly during a run helps compensate for the loss of fluid through sweat and prevents dehydration.

Before falling into the opposite extreme, it is worth recalling a constant in sports nutrition: the key is to maintain a subtle balance. While it is possible to become dehydrated, it is also possible to drink too much: this is hyponatremia. This is a trap beginners often fall into when following the advice of more experienced runners who sweat much more and therefore need a greater fluid intake.

It is also important to keep in mind that we are not all equal when it comes to sweating, so our hydration needs simply cannot be compared or extrapolated from one runner to another based solely on their pace. Height, weight, and sex, among other factors, affect the amount of sweat produced. As is often the case, there is no magic formula; you have to learn about yourself and gradually discover what works by trying and sometimes failing. Pay attention to your hydration level, as this can make the difference between a session where you feel comfortable and good and one where you have to put in far more effort than you should.

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Finding the right balance

To protect against hyponatremia or excessive hydration, isotonic drinks containing sodium may be preferred to plain water. Indeed, while sweat is primarily composed of water, it also contains minerals, lactate, and urea. This is the main benefit of isotonic drinks: not only do they allow you to maintain proper hydration, but they also replace all the substances lost through sweat besides water.

Indeed, when you are overhydrated, your sodium level is low and your blood volume is reduced; consequently, an antidiuretic hormone (ADH) is produced and retains water in your body. This lowers your sodium level again by diluting the blood... A vicious cycle that must be avoided at all costs.

Excessive hydration is actually more dangerous than dehydration: it can be fatal. Thus, while there is no single best practice that can be recommended to everyone, this advice can nevertheless be universal: pay attention to your level of hydration during exercise; finding the right balance is something that happens gradually as you gain experience from running.

In summary: a little advice

Compared with intestinal cramps, this point can be important because if sugars and water are not absorbed, they stagnate and "ferment" inside the intestines and there you have it... the cramps.