The purpose of the study is to evaluate the feasibility of a new wearable computerised system designed for an ongoing monitoring of sportsmen under real-life conditions. This system consists of different sensors and Bluetooth Transmitters interconnected by wires and integrated in the textile of a T-shirt. Several physiologic parameters including bioimpedance should be investigated under conditions relevant for an intensive physical activity, like high body temperature or partial dehydration. This system has to be tested under laboratory and "natural/open air" conditions, the obtained evaluations compared with standardised established diagnostic methods.