Water is essential for our body: more than 60% of our weight is made up of liquids. The analysis of fluid loss during sports performance is crucial for an athlete, as intense sweating can cause dehydration. It can lead to worsening of sports performance, cardiovascular fatigue and, if prolonged and in extreme situations, even hyperthermia, failure of the gastrointestinal system, heat cramps and death. Fluid balance, i.e. the optimal ratio between fluid intake and loss, is critical to athlete performance and safety during exercise, especially in extreme environmental conditions such as high-temperature environments. Being able to perform a fluid loss analysis in a short time and with precision is certainly useful to optimize training and physiological recovery.