Water and Sodium
Water
Average water losses when playing a sport are from 1 to 3 litres/hour (up to 10 litres/hour in extreme cases).
Dehydration is a cause of reduced performance once 1 to 2 % of body weight is lost (0.7 l to 1.4 l for a person weighing 70 kg).
At this stage, the reduction in muscular efficiency has already reached 10%! Beyond 4%, you can experience great fatigue, heavy legs, breathlessness, confusion, ...
And beyond 6-8%, the risk of accidents arising becomes significant (exercise heatstroke...).
You must always hydrate yourself before you start to feel thirsty, because this only appears once you are already dehydrated. Train yourself to hydrate yourself well, to anticipate thirst and dehydration!
Brief or prolonged, all exercise requires the right hydration, which must be adjusted depending on the duration and intensity of exercise. To avoid dehydration, you have to take account of heat losses that vary according to weather conditions (temperature, wind), the level of training and clothing. Remember, the state of fatigue and stress are factors conducive to dehydration
Be aware that being perfectly hydrated before exercise is essential to good performance and prevention of muscular accidents during exercise.
Sodium
Secretion of sweat creates an interest in electrolytes (sodium Na+ and chloride Cl-).The more the volume of sweat rises, the more your electrolyte concentration falls.
During prolonged exercise (3 to 4 h), the quantities of sweat lost can reach 7 to 8 litres. The risk is therefore of hyponatraemia (lowering of blood sodium concentration), expressed as muscle cramps, behavioural problems, even a loss of consciousness.