ABSTRACT
During physical work, all systems and organs of the human body are involved: the muscular system is the effector of the central nervous system, which requires the other systems to supply muscle tissue with energy to maintain motor activity. Muscle contraction during physical exercise is possible due to energy transformations from chemical energy stored in the bonds of molecules in different metabolic substrates into mechanical energy. Adenosine triphosphate (ATP) is an intermediary molecule throughout these processes. Three energy systems in which ATP resynthesis takes place depend on the intensity and duration of physical exercise. These are the phosphagen, glycolysis, and aerobic systems. The phosphanenic system or alactical anaerobic system provides energy at the beginning of any physical activity and for activities of very high intensity and short duration. Electrocardiographic recording systems allow for continuous monitoring of the heart and evaluate changes during exercise and recovery.
