Hydration needs

How much water per day according to your profile. A 2% drop in water weight reduces performance by 10-20%.

Why hydration is underrated

A loss of just 2% of body weight in water reduces aerobic performance by 10-20%, increases perceived exertion, and increases the risk of cramps and injury. However, 60-70% of amateur athletes arrive at training already dehydrated.

Calculation method

Base: 35 ml/kg/day (EFSA / French Nutrition Society recommendation).
Effort: +500-800 ml per hour of sport (average 600 ml/h, more in long endurance).
Climate: factor 0.9 (cool) to 1.3 (very hot) to adjust sweat losses.

Before, during, after training

Before

Drink 500 ml in the 2 hours before exercise. No soda or excessive coffee (moderate diuretic effect).

During

150-250 ml every 15-20 min depending on intensity and temperature. Beyond 60 min of effort, include electrolytes (sodium 300-700 mg/L) and carbohydrates (30-60 g/h).

After

Compensate 150% of the weight loss observed by weighing before/after. Example: 1 kg lost = 1.5 L to drink within 4-6 hours.

How to know if you are well hydrated

Color of urine: pale yellow = good hydration; dark yellow = to be corrected.
Vircination frequency: 5-7 times/day is normal.
Thirst: If you feel thirsty, you are already 1-2% dehydrated. Don't wait.

Individual sweat losses

Very variable: 0.5 to 2 L per hour depending on the athlete, intensity and heat. To estimate your personal level: weigh yourself naked before exercise, weigh yourself after (without wet clothes), add what you have drunk. The difference in kg = your sweat losses in L.

Water or sports drink?

Effort < 60 min: plain water is enough.
60-90 min or intense effort: water + pinch of salt + a little quick sugar.
Effort > 90 min: exercise drink (30-60 g carbohydrates/h, 300-700 mg sodium/L).
Extreme heat: electrolytes even for short efforts.

Caffeine, alcohol and dehydration

Coffee (up to 3-4 cups/day) has a mild diuretic effect, usually offset by the water it contains. Alcohol, on the other hand, is strongly dehydrating: 1 glass = 100 ml of additional water to compensate. To be limited before or after a big session.

À consulter aussi

TDEE Apport énergétique global Calcul des macros Compléter avec les nutriments Calories brûlées Estimer la durée d'effort Besoins en protéines Récupération musculaire

Questions fréquentes

More or less depending on your weight and activity. The 35 ml/kg rule gives 2.1 L for 60 kg, 2.8 L for 80 kg. To be supplemented with water intake through food (fruits, vegetables, soups).

Yes, rare but possible (dilution hyponatremia). Appears especially in ultra-long endurance sports when you drink a lot of pure water without sodium. Beyond 6-8 L/day without extreme heat or long exercise, it is too much.

No. It is even recommended for digestion and hydration. The myth that water “dilutes” digestive juices is false.

Yes, 80-90%. The diuretic effect of normal doses (3-4 cups/day) is largely offset by their water content. Only the very high dosage of caffeine (> 500 mg/day) can be dehydrating.