Hypotonic, Isotonic, Hypertonic. What’s the difference?

22 November, 2012 | Written by Recuperat-ion Recuperat-ion


What´s an Isotonic, Hypertonic and Hypotonic solution? 
understand what the terms isotonic, hypertonic and hypotonic mean, it is
necessary to go a few years back and remember the experience that we all had ​​in school.
In this experiment, we start with
an initial observation: any liquid
contains dissolved substances, even pure water
. These dissolved substances
may be mineral salts and trace elements (like in pure water), glucose (like in
the syrup with water), vitamins, antioxidants, fructose (like in fruit juice.)…
Consequently, the more a liquid contains dissolved
substances, the less it contains available water
: therefore the thicker and
concentrated it is, the less aqueous it is and the less it moisturizes…
This is where comes “the experience”:
when you put in contact two solutions with a different concentration of
dissolved substances,  the substances from the more concentrated
solution migrate towards the least concentrated solution and the water makes
the reverse path.
This until having the perfect balance of concentration of
dissolved substances between the two solutions.
Conclusion :      
1) When we absorb a drink with a higher
concentration of dissolved substances than the liquids in our body, water does
not migrate from the drink towards our body but primarily in the opposite
direction. Dehydration first occurs.
This situation describes a hypertonic concentration.
2) When we absorb a drink with a lower
concentration of dissolved substances than our internal liquids, water migrates
first from the drink towards our body. Rehydration first occurs. This situation
describes a hypotonic concentration. The isotonicity describes the perfect
balance between the concentration of the drink and our internal liquids.
What is an isotonic, hypertonic and hypotonic sports drink?
After the little experiment we just
described, we understand that:
1) A hypertonic drink is a drink with
a higher liquid concentration than the one in our body.
2) A hypotonic drink is a drink with
a lower liquid concentration than the one in our body
3) An isotonic drink is a drink
with a liquid concentration equivalent to the one in our body.
For the same
volume of water (eg an 800ml bottle,) the concentration of a sport drink can vary depending on the number of powder
scoops you add in it. The drink obtained is then either hypertonic or
hypotonic or isotonic. Manufacturers’ recommendations are set by default to
obtain an isotonic drink.
What is the advantage of an isotonic, hypertonic and hypotonic drink?
A drink is isotonic when its
concentration (called osmolarity) is equal to the concentration inside the body
(the dissolved substances of the blood are in the blood plasma). The most basic
recipe to obtain an isotonic drink is to dissolve some sugar and salt in water,
in proportion of 25g of sugar for 500ml of water and 1g of salt for 500ml of
All commercial preparations (sports
drink in powder) are designed to produce isotonic drinks. They differ from each
other depending on the ingredients (glucose, fructose, sodium, potassium,
magnesium, antioxidants, vitamin B1, B6 …). As seen above, by simply
adjusting the recommended dose, we can obtain an isotonic, hypotonic or hypertonic
The prolonged physical exercise
requires water, sugar, mineral salts and group B vitamins, principally to
compensate the body losses. It is known that a decrease in any of these
elements, including water and sugar, reduces the performance level during the
physical activity.
1) A hypertonic drink compensates more the sugar loss and less the
water loss.  A decrease in the body water
reserves may result in a decline in performance (dehydration). However,
hypertonic drinks can be adapted to specific situations such as extreme weather
environments (extreme cold).



2) A hypotonic drink compensates
more the water loss and less the sugar loss. This type of drink is more
suitable for prolonged endurance exercise, in warm environment, where the
priority is to compensate water loss by drinking. A hypotonic drink reinforced with
mineral salts helps compensate the sodium loss and therefore avoid the decrease
of plasma concentration in sodium, which consequences can sometimes be severe
(hyponatremia). The risk of digestive disorders with this type of drink is also


3) An isotonic drink compensates in a balanced way water loss and
sugar loss. In situations of intense exercise, an isotonic drink is more
adapted to maintain a level of performance, as it better preserve both water
reserves and sugar reserves in the body. Furthermore, the presence of all of
these constituents in a specific proportion contributes to a better
assimilation of each element and a reduced risk of digestive disorders.
Some examples of common hypotonic, hypertonic, isotonic drinks
1) Example of common hypotonic
drinks: plain water, unsweetened tea, Recuperat-ion Sport…
2) Example of common hypertonic
drinks: grape juice, Red Bull
3) Example of common isotonic
drinks: only drinks called “the effort of carbohydrate” carrying this
David Padaré:
Dietician nutritionist specialized in preferred disciplines such as
endurance sports and outdoor running, trail running, cycling, triathlon,
David Padare accompanies many athletes in their diverse and varied
challenges: ultra trail, trails stages, marathons, 100kms, 24h….
Member of the AFDN (French Association of Dietitian Nutritionist) and
the nivernais network RESEDIA for the management of DIABETES and OBESITY, he
also put his knowledge to the treatment of pathologies such as obesity,
diabetes, heart disease, food allergies…
Find David in magazines such as Running Coach and Cyclo Coach
Cyclosport, Running attitude trail magazine, running 100%feminin, nutricycle.comcourirdeplaisir.com, nutritiondusportif, traileur outdoor zsport.com…..
Nuteoconsult is the structure founded to bring together expertise from
various backgrounds (diet, coach, mind trainer…) for one purpose: to provide
simple and clear answers to each level of practice.

Recuperat-ion – Hydration and Nutrition Experts


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