The human body is composed of about 60% water (50% for women). A sedentary adult needs to consume about 1 ½ to 2 litres of water a day. A physically active person obviously needs more, depending on his level of activity. Dehydration has a very important effect on both physical and intellectual performance. It is known, for example, that a loss of body weight of 2% due to dehydration reduces physical ability by 20%!

And the greater the level of dehydration, the more unpleasant the side effects: digestive problems, blurred vision, poor reaction times, a diminished ability to concentrate, etc…

Our advice: drink before you feel thirsty. Your body has actually started to become dehydrated long before you are aware that you are thirsty. It is preferable to drink small quantities of water throughout the day, rather than only drinking at mealtimes. During any physical activity, it is essential to drink more than you normally would, also in small quantities, throughout the period of activity.

Water circulates throughout our bodies. We are constantly absorbing it and eliminating it. The healthy human body needs to adapt its consumption of water to the amount it loses every day.

"Output" of water: the adult human body loses 2 to 3 litres of water per day. Kidney function accounts for half of this loss (through urine), while the other half occurs by other means (through the skin, in respiration, and during digestion).

"Intake" of water: all water that is lost needs to be replaced. Thus, our daily intake of water should be in the realm of 2 to 3 litres. This daily intake is shared between endogenous sources of water (i.e. water that is produced by the human body itself), and exogenous sources (i.e. water contained in the drinks and food we consume). These 2 sources of water, while significant, are not sufficient to ensure that we maintain a healthy level of hydration. It is therefore essential that we consume about 1.5 litres of water per day, or approximately one glass of water per hour between meals.

Keeping properly hydrated is essential to the practice of any sport. Here are the 10 golden rules as to when and how to take in fluids:

1. Before the period of physical activity, and in particular during the half hour that immediately precedes it, drink up to ½ litre of water (about 3 glasses), in small sips. To begin the event in optimal conditions, drink 0.15 to 0.25 litres of water (one glass) with added glucose during the 15 minutes before the start.
2. During the period of physical activity, if possible, drink small sips of water, in a reasonable quantity, but not so much that it will overload your stomach and cause you to get a stitch. Avoid fizzy drinks which can cause your stomach to become bloated.
3. It's not absolutely necessary to drink water during the physical activity if this lasts for less than 30 minutes. If you plan to exercise for a period of 30 minutes to 3 hours, and at an increased intensity, it is preferable to drink regularly - every 15 to 20 minutes. According to your level of perspiration, you should drink between 0.5 and 1.5 litres of water per hour, with added glucose. If your period of activity is to exceed 3 hours (an endurance sport), you should spread your intake of fluids evenly throughout the exercise, at intervals of 30 minutes to one hour, with 0.4 to 1 litre consumed per hour.
4. If it is warm and you happen to pass by a drinking fountain, don't hesitate to splash yourself with water (your legs in particular), as this will help in the regulation of your body temperature.
5. Don't wait until you feel thirsty to drink. Once you are thirsty, it is already too late. Think ahead, and drink a little after the first 15 minutes of activity.
6. Drink regularly after you have finished exercising, so as to eliminate toxins and drain the impurities that were accumulated during your effort. It is vitally important that you restore the amount of water in your body as well as your reserves of energy as soon as possible after the exercise or event has finished, drinking between 0.5 to 1.5 litres of water per hour at even intervals.
7. Even if you are "dying" of thirst, do not take in a large quantity of liquid all at once, as, again, this could lead to stomach problems.
8. Make sure that you compensate for the loss of water and essential nutrients due to your physical activity by drinking at regular intervals, so as to delay muscle tiredness.
9. The water you drink should be at a temperature of 10 to 15°C. If your drink is too cold, or iced, you may end up with intestinal problems.
10. Depending on the intensity of your physical exercise and the ambient temperature, you should consume somewhere between 2 and 4 litres of water on a daily basis.

A plethora of different types of mineral water can be found in today's supermarkets. However, not all types of mineral water have the same properties. Each one should be consumed in moderation, and each is useful in its own way.

Water on its own does not provide us with energy. However, it appears that our muscles, blood cells and even our brain have very specific requirements with regards to the quality of the water we drink. In fact, our vital organs rely on high energy substrates and minerals rich in trace elements to ensure their peak performance in specific situations (endurance sports, high intensity activity, very high temperatures). Plain tap water is simply not sufficient in meeting the body's needs in these situations.

In order to avoid physical and physiological deficiencies, we should therefore include" isotonic" and/or glucose-polymer based drinks among the liquids we consume. The advantage of these so-called "sports drinks" is twofold: they provide our organs and tissues with the energy they need, while at the same time ensuring we are absorbing enough fluid.

Tap water is still advised for daily use, however, as is spring water, which has the additional benefit of a diuretic effect, thus helping to eliminate waste, both in the morning before eating, or at a time of significant muscle fatigue.