What is the use of isotonic drinks?

Isotonic drinks, energy drinks or effort drinks, there are a whole range of names for drinks for athletes. These drinks are becoming more and more popular. But what do these terms means? Are they the same? How should you take them? We will tell all!

What is an isotonic drink?

Isotonic drinks, energy drinks and effort drinks are all the same thing, namely drinks for athletes.

A drink is isotonic when it contains the same particulate concentration as blood. In order to determine this, we study the osmolarity of the drink, which must be between 270 and 330 mOsml / litre in order to be isotonic. So, a drink is hypotonic when less concentrated than blood and hypertonic when more concentrated.

All drinks designed to meet athletes' needs during effort must be isotonic or slightly hypotonic, but never hypertonic.


Why should I use isotonic drinks?

The purpose of an isotonic drink is to improve the intake of water, minerals and nutrients to facilitate the replacement of what the body uses during effort. It facilitates rehydration, while contributing to the proper assimilation of the particles needed to support effort (glucose, sodium etc.)

An isotonic drink is easily absorbed and quickly leaves the stomach, to ensure optimal efficiency and comfortable digestion.

A hypotonic drink is less easily absorbed than an isotonic drink, but may be useful in very hot weather.

A hypertonic drink is too concentrated and take too long to leave the stomach, which may cause digestion issues, potentially causing dehydration through a demand for water in the stomach to dilute the concentration.

It is essential that you respect the doses shown on the packaging of your drink to make the most of its isotonic properties.



What does an isotonic drink contain?

-          Water is the main ingredient of the drink. It ensures hydration during effort.

-          Carbohydrates to ensure energy intake and enable continuous physical effort. The quantity of carbohydrates in a drink must be between 60 et 80 g / litre.

-          Sodium to recover salts lost in sweat. In addition, sodium triggers a sensation of thirst and makes it easier to assimilate water and carbohydrates.

-          Group B vitamins to facilitate the transformation of into energy and help combat fatigue.

-          Potassium is useful in hot or warm weather.

-          Magnesium to help reduce fatigue.

-          Antioxidants to help the body defend itself against certain toxic waste produced by cell activity.

-          There may be protein in the drink, but this is rare. It may be helpful over long periods of effort, i.e. more than 3 hours.


When should I have an isotonic drink?

Endurance sports, such as triathlon, involve a risk of dehydration through perspiration. Sweat is composed of water and minerals (mainly sodium, but also a little potassium). During effort, the body may lose over one and a half litres in perspiration an hour, and sometimes up to 3 litres an hour. So, unless this loss is balanced by drinking, the body becomes dehydrated. Moreover, we know that muscles use energy during effort, so regular carbohydrate intake enables us to make up for losses and maintain effort.

Isotonic drinks are the best solution, since they provide water, sodium and carbohydrates. They are 'all-in-one' drinks.

After an hour of effort, you will thus need to drink isotonic drinks regularly. The required dose is 1 mouthful every 10-15 minutes from the start of your effort.


photo conseiller

Marie Fauchille

Diététicienne - Nutritionniste, passionnée de raid multisport et d’aviron


Triathlon is a demanding sport where every detail matters, i.e. technique, experience, mental management, equipment and, of course, nutritional strategy. Hydration is one of the keys to completing a triathlon.
I am sure you have often heard people talking about recovery drinks, but do you know exactly why they are useful? What are the benefits, especially for a sport such as triathlon?