RÉSUMÉ

A survey of 29 trained and untrained youths aged 18 to 20 years was carried out. It has been shown that the optimal level of adaptation of a trained body to prolonged and intense physical exercise is provided by the activation of not only the constitutive calcium-dependent nitric oxide synthesis, but also by oxidative arginase metabolism of arginine, which yields a range of important low-molecular bioregulators and antioxidants, including urea. Significant reduction in the functionality of the body of trained youths at the end of competition period and as a consequence the manifestation of disadaptation signs correlates with increased oxidative calcium independent nitric oxide synthesis and its non-oxidative synthesis due to reutilization of stable circulating NO metabolites.