Hydration of the athlete

During a sports activity, most of the energy produced by your muscles turns into heat. To evacuate this excess heat, the sweat mechanism kicks in. Sweating generates water losses that must be compensated to maintain your physical and mental abilities.

The risks of poor hydration


When you do not drink enough to compensate for water loss, you may find yourself dehydrated. The heart has to work harder and the heat regulation mechanisms are outpaced: the heart rate increases, the blood pressure decreases and the body starts to « overheat ».

Just a slight water deficit of the order of 1% of body weight, or only 0.7 liters for a man of 70 kg, will reduce performance by 10%: the athlete can feel fatigue, headache, nausea, heaviness in the legs, shortness of breath … In addition, an athlete who is dehydrated in a repetitive manner may suffer from muscle, tendon and ligament pains; the risks of breakdown and sprains are increased.

Heat stroke

When dehydration becomes too high, the blood volume decreases. The brain and the heart are not getting enough blood. To preserve them, the body tries to increase the circulation: it closes the vessels leading to less essential areas like the skin. The body temperature continues to rise while the cooling mechanism, sweating, is no longer effective. The difference between heat produced and heat evacuated is too great: it is a heat stroke!


The movement of the muscles is achieved by the contraction of fibers inside the muscle cells. The contraction is done through ion exchanges, mainly potassium, sodium, magnesium and calcium ions. Dehydration can lead to an imbalance of ion exchange, especially via sweat which makes us lose a lot of sodium: cramps are then manifested. This is the most common alter symptom of poor hydration (in quantity or quality).

Drink little but often

If the amount of drink absorbed is too much, only a part will be really used and the rest will be sent almost directly into the bladder. In addition, the drink is less well accepted during physical activity: a large volume can distend the stomach and hinder exercise. During exercise, hydration should be divided every 15-20 minutes per volume of 100-200 ml. Be attentive to the weather conditions and do not hesitate to take a larger volume in case of extreme heat.

Drink choice

For a physical activity of less than 1 hour, only hydration is recommended and the best source of hydration is water.

After 1 hour of physical activity, the body needs a « boost »: you must then add simple sugars and minerals in your water.

A sport drink must contain:

  • 60 to 80 g of carbohydrates per liter (i.e. 6 to 8 g / 100 ml) in the form of sugar, glucose, fructose, possibly maltodextrin
  • 500 to 700 mg of sodium per liter (without exceeding 1 g/L).

There are ready-to-use powders, but it’s possible to make yourself a sport drink with simple ingredients.

Here are two examples of sport drinks:

  • Mix 500 mL of pure fruit juice and 500 mL of water and add a pinch of salt (¼ teaspoon)
  • Dilute 60 g of syrup / sugar in 1 L of water with a pinch of salt.

Adapt the flavors to your liking to find your magic potion!

It is with experience and after a few experiments that you will know the formula and the volume that suits you.

To read also: my article « Water, an essential need for the body »

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