14 trained and 21 non-trained girls 18-22 years of age have been inspected. We found that systematically trained girls had a higher level of nitric oxide synthesis through calcium-dependent L-arginine oxidation by constitutive NO-synthase isoforms (eNOS, nNOS) and through reduction of stable oxidized NO metabolites. NO synthesized de novo in calcium-dependent path­way provides a long-term organism adaptation to physical loads of high volume and intensity at the beginning and in the middle of stress-aggravated competition period. At the end of competition period we detected significant activation of induc-ible calcium-independent de novo NO synthesis from L-arginine.