Objectives: Normal and moderate exercise can stimulate the immune system. Acute and chronic exercise is a stress, which may have harmful consenquences leading to marked changes in the hormonal, neuroendocrine and immune systems. However, maximal acute and long-term exhaustive exercise may cause opposite profound changes. The aim of the study was to determine the acute and long-term effects of exhaustive exercise on the immune and endocrine systems. Study design: We investigated 20 top sportsmen between the ages 16 to 18 years. Blood samples were collected before exercise, immediately after exercise on a treadmill and after 60 minutes of regeneration. To determine the long-term effectes, the investigations were performed repeatedly every 3 months during a one-year period. Absolute and percentage counts of lymphocytes and their subsets - CD3 + , CD3 + CD4 + , CD3 + CD8 + , CD3 - CD16/56 + , CD19, CD3 - CD8 + were determined by flow cytometer. Results - I. acute exercise: Immediately after acute exercise we observed a significant increase of absolute counts of T lymphocytes and their subsets - CD3 + , CD3 + CD4 + , CD3 + CD8 + , CD3 - CD8 + - followed by a significant decrease after 60 minutes of regeneration. The most marked differences after acute exercise were found in the NK cells, which are assumed to be responsible for defence against viruses and malignancy cells. The mean values of th e NK cells were 340 cc/ml before exercise, 1220 cc/ml immediately after exercise and 130 cc/ml after 60 minutes of regeneration. Results - II. chronic changes: There was a significant decrease of percentage counts of CD3 + CD8 + T lymphocyte subsets and NK cells (CD3 - CD16/56 + ) after one hour of regeneration. In our opinion, these changes may be due to the higher training intensity and may be significant mainly in subjects with daily exhaustive exercise called the „open window“. Conclusions: Our results indicate, that exercise may induce redistribution of lymphocytes between the peripheral lymphatic tissue and the circulation. This may be due to muscle damage, increase of IL6 levels, stimulation of the neuroendocrine system and increased expression of adhesion molecules. Repeated and exhaustive long-term exercise modifies the immune response and may predispose individuals to more frequent respiratory viral infections, chronic fatigue syndrome or opportune viral (CMV, EBV) and parasitic (e.g. toxoplasmosis) infections. These facts should be taken into consideration during planning of exercise schedules of top sportsmen.

        Key words: maximal acute and chronic exercise, changes of the neuroendocrine and immune systems,