Oral administration of green tea extract in a dose of 6 mg/kg twice a day (before and after exercise) over 2 weeks significantly increased swimming times on week 1 and 2 in comparison with control animals receiving water. The 7-day and final exhaustive running in rats was accompanied by a significant decrease in spleen weight and iron serum levels associated with developed reticulocytosis. Administration of green tea extract in a dose of 12 mg/kg once a day (before exercise) for 2 weeks did not affect the duration of the running, but prevented the decrease in serum iron and spleen weight, that, along with a significantly increased concentration of reduced glutathione in erythrocytes, can indicate a normalizing effect of green tea extract on hemopoiesis and stimulating effect on the antioxidant system of erythrocytes.