Understanding the metabolic processes and physiological characteristics of organic systems are the key starting points for the successfull implementation of the training process and the improvement of competitive performance. The cardiovascular system is responsible for circulation and oxygen supply to active muscle tissues, and it adapts through the regulation of heart size, stroke volume, heart frequency, blood flow and heart minute volume. The respiratory system has lungs in its center, and it goes through changes in the diffusion capacity in the organism, breathing stimulation and in the maximum receipt of oxygen during the muscular work. Metabolic processes during training are complex, and we can act on each one through the training process. Three basic metabolic routes for supplying the organism with ATP can be outlined, namely the phosphocreatine-creatine system, the glycogen-lactic acid system and the aerobic system. The thermoregulation of an organism is conducted through hypothalamus, which serves as organism’s thermostat, while the body releases heat through the processes of radiation, convection, conduction and evaporation. In order to improve competitive results, training in different environmental condictiones was introduced, such as training in the warm and cold, at altitude and at great depths. During the change of environmental conditions, the body goes through numerous physiological processes, which leads to adaptation.