Rats were subjected to different running trainings on a treadmill for 3 weeks, including continuous endurance and intermittent exercises at speed intensity of 10,22 and 30 m/min (°15), respectively. On the last day of the training period, the animals were dosed with Nw-nitro-L-arginine methyl ester, L-NAME (30 mg/kg b.w.), and they were further subjected to exhaustive running exercise (22 m/min; °15). Studies showed that inhibition of nitric oxide synthase (NOS) with L-NAME mitigated pro- and anti-oxidative (TB/TA) balance in the blood plasma of rats subjected to exhaustive exercise. Intermittent training before the exhaustive exercise enhanced L-NAME-induced effects on TB/TA levels in rats, but it was not observed in continuous endurance trainings