Bodybuilding 5 MIN READ 870 VIEWS October 23, 2016

Isotonic Drinks for Athletes

Written By Archana

An isotonic drink for athletes has sugar content between 4g and 8g per 100ml, which mimics your body fluid.

The episodes of dehydration are common in sports, especially in a hot and humid country like ours. Technically, dehydration means losing water and salts, via perspiration and casts a negative effect on athlete’s performance. To think about it, dehydration in mild form can spell the difference between a gold and silver medal. In an extreme form, dehydration affects vital organs, such as the kidneys, brain and heart, as they require a minimum of water and salt.


When you start an intense activity, like a competitive sport or running a marathon, your heart rate goes up. You start feeling flushed, which signals the body to resort to its cooling mechanism, sweating.  Meanwhile, as your body continues to tap into the glycogen reserve of liver to fuel the intense exercise regimen you begin to feel thirsty. The intensity of your activity will remain as long as the glycogen reserve lasts but as your tank empties your body is going to switch to burning fat, a less efficient source of fuel and you will feel all the more thirsty.


The core temperature of our body is 370 celsius to 98.6 degrees Fahrenheit. When athletes engage in sports, their heart rate goes up, as a result sweating occurs to maintain the core body temperature, thereby resulting in the loss of body fluids and minerals, such as chloride, calcium, magnesium, sodium and potassium, collectively known as electrolytes. Calcium is useful in muscle contractions, potassium keeps blood pressure level stable, magnesium stablises protein-fluid balance and sodium along with chloride helps maintain fluid balance.

% Body Weight Lost as Sweat Physiological Effect
2% Impaired Performance
4% Weakness and inability to do muscular work
5% Heat exhaustion
7% Hallucinations
10% Circulatory collapse and heat stroke


An intense physical activity, like running a marathon or playing a competitive sport diminishes your glycogen stores. Glycogen is the longer chain version of glucose and they are stored in the muscles and the liver. The normal body stores of carbohydrate in a typical athlete are:

70kg male athlete Liver glycogen 90g and muscle glycogen 400g
60kg female athlete Liver glycogen 70g and muscle glycogen 300g

During hard exercise, your body consumes 3-4g of glycogen per minute. If your activity lasts for 2 hours or more, a very large fraction of stored glycogen will be exhausted. If these carbs are not supplied in time, recovery of the muscle and liver glycogen stores after exercise will require 24-48 hours.


It’s a no-brainer that heavy sweating leads to fluid loss. For a pound (453g) of weight loss due to physical activity, you need to drink 16 ounces (approx. 2 cups) of fluid to rehydrate your body.  How much of the fluid intake will be retained by your body depends on the speed at which it is emptied from the stomach and the rate at which it is absorbed through the small intestine.

Drinking plain water is not good for rehydrating, as it is not retained efficiently. Moreover, it contains neither carbs nor electrolytes. ​


Normally, any rehydrating liquid contains dissolved substances, even plain water has minerals. The other such rehydrating liquids like sports drink have glucose with water or antioxidants. Now, going back to the school science lessons, when two liquids of varying concentrations meet, the one with more concentrated solution moves towards the lesser concentrated version. Rehydrating drinks or sports drinks are of three kinds: isotonic, hypotonic and hypertonic.

A hypotonic drink has less liquid concentration than your body. It contains less than 4g of cabs per 100g. It functions well as a thirst quencher, but falls short on energy.  Your body absorbs hypotonic sports drinks more quickly than water and it is ideal for less strenuous sports, primarily recreational in nature. A hypotonic drink quickly replaces fluids lost by sweating. It is suitable for athletes who need to replenish their fluid intake without the additional boost of carbs, like jockeys and gymnasts.

A hypertonic drink generally has more than 8g of sugar (carbohydrates) per 100ml and is thicker than bodily fluids. It is primarily intended to supply energy. Hypertonic drinks are taken up more slowly than water. Hypertonic drinks are helpful for sportspersons who need more energy during their training to top up their glycogen stores. You need to have a hypertonic drink along with a hypotonic drink to replace fluids.

The higher concentration of sugar also makes it ideal for less strenuous, long duration exertions such as studying (the fuel for the brain is glucose), driving, gaming, etc.


Years of research have suggested that the correct concentration of carbohydrate in your drink is about 5 to 7 percent.  An isotonic drink for athletes generally has sugar/ carbohydrates content in this per 100ml, which mimics your body fluid.  Your body absorbs isotonic drink more quickly than water.  Not only these drinks quench thirst quickly but also are an ideal solution for endurance sports.

1.       Replenishes Electrolytes

As compared to hypotonic, hypertonic and energy drinks, isotonic drinks replenish electrolytes in a better way. A 1998 study from Netherlands published in the International Journal of Sports Medicine compared the after effects of a caffeinated drink, a low-sodium mineral water and an isotonic carbohydrate-electrolyte solution on cyclists. Those who consumed isotonic drinks were able to retain more sodium, magnesium and calcium in their bodies, even after urinary and sweating losses.

2.       Faster glycogen top-off

For athletes, glucose remains the quick-acting source of energy, but the drawback is that there is a limited store of this energy in the body. A two-hour intense workout is enough to exhaust the glycogen reserve of the athlete and it takes more than 24 hours to return to its original level. An isotonic drink quickly tops off the glycogen level.

3.        Better hydration

The question remains why you even need such rehydrating solutions. Why can’t plain water do the trick? Since water exits quickly from your system it makes you feel bloated.

4.        Improved endurance

As compared to a placebo, the hydration offered by isotonic drinks is 24 percent higher. The research was reported at the European Journal of Physiology in 1990.

The benefits of isotonic drinks will reflect in your intensity and duration of workout and sports event. Choose an isotonic drink, like MuscleBlaze Isotonic that contains along with sugar, amino acid-like glutamine to speed up your recovery process.

Read these next