Osmolarity - what is it and why is this topic important for endurance athletes? Many have already experienced it, the gastrointestinal tract simply does not want to absorb anything more during an exertion. It comes out above or below again, a break off of the training or competition is imminent. But where does this actually come from?

Under physical stress, it is more difficult for our body to absorb nutrients. It also reacts more sensitively to intolerances and excessive amounts.

If we take a closer look at the interrelationships, we can quickly pinpoint some of the main causes.

1. the amount of carbohydrates (KH) consumed per hour is too high.

Even professional athletes rarely manage to consume more than 100g of KH per hour in competition, for hobby athletes it is usually more like 70 - 80g.
(Important: only the KH are meant here, not the total amount of the gel, bar or drink).

2. there are incompatibilities with the ingredients of the supplied beverages or food, more about this in a later chapter.

3. too many things that are actually not necessary during the load are consumed. And here we are already at the concept of osmolarity.

Was bedeutet dieser schwer auszusprechende Begriff “Osmolarität” denn nun eigentlich?

Quite simple. We talk about the osmotic pressure of a solution in terms of the pressure of the dissolved particles relative to each other. Osmolarity is therefore the physical quantity of the pressure of the dissolved particles in a beverage or a gel.

For us, however, something else is decisive: The higher the osmotic pressure or osmolarity, i.e. the more dissolved particles, the slower our digestive system can metabolize the whole.

What can I conclude from this for my sports nutrition?

Under stress, especially in competition, it is important to relieve the digestive system and still absorb the supplied nutrients quickly and without complications. Consequently, we should make sure that we only take in what we really need.

Because if unnecessary ingredients are added in gels or drinks, the osmolarity increases and thus the absorption rate in our body slows down to the point that nothing works at all.

To our horror, we recently discovered gels containing flavor enhancers at a very large triathlon event. About the sense or nonsense everyone must then think for themselves.

Was Athleten über “isotonische Gels” und isotonische Getränke wissen sollten

At this point, a very important note on allegedly "isotonic gels" offered on the market:
Due to the high number of dissolved particles, a gel is always hypertonic in relation to the body, i.e. there are always significantly more particles dissolved in a gel than in the blood.

Die Sportphysiologie fordert von einem Sportgetränk, das zur schnelleren Aufnahme im Darm isotonisch sein soll, maximal 8 g Kohlenhydrate pro 100 ml Getränk. Wird dieser Wert überschritten, so ist das Getränk oder das Gel hypertonisch (hyper = über). Klassische Gels beinhalten ca. 60 – 70 g Kohlenhydrate je 100 g, auch viele sogenannte “Iso-Gels” sind daher meist hypertonisch und nicht isotonisch.

This is also the reason why water should always be drunk with an energy gel.
(With so-called drink gels or iso gels, the athlete can do without water intake for very short units up to a maximum of 2 hours).
The aim here is to dilute the gel in the stomach with water so that the food pulp contains a maximum of 8 g of carbohydrates per 100 ml (approx. 100 g) so that it can be absorbed quickly.

So an energy gel really makes sense, because the high energy density per volume makes it easy to carry the energy you need for training and competition in your jersey pocket.

By the way, if you want to be safe, you should consider that for "normal" loads up to the Ironman distance in triathlon, you really need the following:
Water, carbohydrates, salt, potassium.

You are welcome to download this article from the series "Das muss mal gesagt werden" as a download as PDF.

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