In order to optimally exercise, the fluid balance must be maintained. Making an effort causes moisture loss, mainly by sweating. If this moisture is insufficiently supplemented, a lack of moisture or dehydration will occur. Dehydration therefore reduces performance and can lead to gastrointestinal complaints, muscle cramps, headaches, ... It is important to start well hydrated and to check the fluid loss during and after exercise controlled. The warmer and humid conditions, the more sweat is produced. In extreme circumstances it is therefore possible to opt for a hydration drink with sodium. Due to the higher salt content the body keeps its moisture better.