What the heck does Isotonic mean anyway??


Dear Roulers,

On my recent Easter holiday I was laid low by a very nasty stomach bug. I’ll spare you the details, but it pretty much ruined my first trip to Kuala Lumpur. I didn’t eat any of the very nice chocolate my wife had bought until I came to Australia. I digress, back to the point of this blog, in the middle of a very average night I’m really dehydrated, I reach into the hotel minibar and find this weird drink called 100Plus.

I’m desperate, so I sip the drink slowly over the course of a few hours. It tastes bland and most importantly stays in my stomach. I look at the can and there’s some blurb about the drink being Isotonic. At the time I wondered what that meant and thought nothing of it.

About month later I’ve run out of Staminade. I’ve been buying the stuff for years as a means of having non-vile tasting liquid to drink whilst cycling.


At this point I’m putting in a shameless plug for Staminade being made here in Australia…how rare these days…and raise a 2 finger salute to another couple of US drinks ending ‘ade’.  I buy another container at local supermarket and I notice that word again ‘isotonic’….hmmm some little gears whirl around in my head….ah ha I’ve made a connection back to that awful night in KL. So what the heck is isotonic? And why is it important.

Enter the science of the sports drink as provided by Google….
The basic theory goes like this. Being hot and dehydrated is bad. I’ll dispense with the explanation. It should be self-explanatory.  Plain water will keep you hydrated not fuel your muscles. Research has shown that body will perform better if your drink contains some carbohydrate. But it mustn’t be too much, fruit juices and sugary fizzy drinks can dehydrate as the body uses available water to dilute them and enable the carbs to be absorbed.

So much to my surprise sports drink can belong to one of three categories: Isotonic, Hypotonic and Hypertonic. Essentially these words describe how rapidly the fluid and carbs are absorbed through the stomach.

Type of Drink Description
Isotonic Drink These drinks are said to be in balance with the body’s fluid levels and empty easily from the stomach into the bloodstream. They contain somewhere in between 5 to 8 grams of carbs per 100ml. Some have sodium to assist absorption. They can be consumed at anytime while cycling.
Hypotonic Drink These drinks are absorbed by the stomach faster than Isotonic ones, but this is achieved by having low levels of carbs. They are very useful for hot conditions, where you are working up a sweat. However as a long distance cyclist you must eat something as well to keep your energy levels up.
Hypertonic Drink These drinks are the slowest to be absorbed by the stomach. They have upwards of 10 grams of carbs per 100ml. They provide plenty of energy, but can hinder hydration, as discussed earlier. They are best consumed after cycling, possibly when you are too tied to eat food.

A word of caution…drinking strong hypertonic fluids can reverse the normal process of osmosis and cause diarrhoea. Think Greg LeMond, Tour de France circa 1986. Which brings me full circle to KL and the 100plus drink in the minibar. Ta da 🙂

Until next time


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