Isotonic, Hypotonic, Hypertonic – which one will be the best for you?

The sufficient amount of fluids consumed is extremely important not only in the context of sports but also in health. However, apart from the amount, the type of drink is also important, especially during the workout lasting over 60 minutes or taking place in high temperature and humidity conditions. An important parameter is the osmotic pressure of the blood. An organism that loses water (as a result of physical activity) first decreases the volume of extracellular fluids, which causes an increase in the osmotic pressure in the body. In turn, differences in electrolyte concentrations cause water to flow across cell membranes until the osmotic pressure is equalized. In professional terms, this term is called isotonia.

    Types of isotonic drinks

    Due to the amount of mineral salts contained in the drinks in relation to the amount of electrolytes in the blood, a distinction is made between hypotonic, isotonic, and hypertonic drinks.

    How does different types of isotonics work
    How does different types of isotonics work

    Hypotonic liquids

    These are fluids that mainly affect sodium retention. They include water and other diluted beverages, for example, vegetable and fruit juices, which primarily contain fewer minerals than body fluids and, importantly, have a carbohydrate content of less than 4g/100 ml. Administering pure water during a long and intensive workout may not be sufficient to optimally hydrate the body, because some of the electrolytes may seep into the gastrointestinal tract – hypotonic drinks are characterized by rapid absorption from the gastrointestinal tract. Hypotonic liquids, on the other hand, are best suited for rehydration on very hot days.

    Isotonic drinks

    Isotonic drinks have almost the same composition as our bodily fluids. The content of carbohydrates is within the range of 4-8 g/100ml. Mineral components are very close to the composition of sweat. Isotonic drinks provide not only electrolytes but also glucose, which allows to save or replenish muscle glycogen. For this reason, isotonic drinks are recommended for people who do more than 60 minutes of exercise. This drink should be consumed during or immediately after a workout when glycogen and electrolytes are rapidly lost.

    If you drink an electrolyte-rich isotonic drink, you should not additionally reach for high-mineralized water. Springwater should be the best choice in such a case. Moreover, remember that if your training goal is to reduce body fat, you should not drink isotonic drinks during the training because the body will use less energy from the fat tissue.

    Hypertonic drinks

    These are strongly sweetened drinks, fruit juices, and carbohydrate supplements. The content of carbohydrates exceeds 8g/100ml. Hypertonics better replenish the components lost during exercise, but on the other hand, their disadvantage lies in the intensification of secretion, or “pulling” water away from the intestines, resulting in a deficit of water in the cells. Hypertonic fluids administered during intense exercise can cause gastrointestinal upset, diarrhea, and a rapid increase in blood sugar levels.