Serum selenium (Se) is a constitutional part of both major plasma selenoprotein P and glutathione peroxidase (GSH-Px), a cytoprotective enzyme against the oxidative damage. It is an accepted fact that any case related to oxidative stress increased by physical exercise changes serum Se levels. In this Study serum Se levels were examined in high physical activity (group I). moderate physical activity (group II), and low physical activity (group III) mates undertaking a soccer-training regimen. In addition, Se changes before and after the acute intensive maximal exercise in an anaerobicloading coordination tests among groups I, II, and III soccer players were investigated. For a minimum of 3 months, the players in group I (n = 12), exercising more than 5 It a week. group II (n = 9), exercising less than 5 h but more than 2 h a week, and group III (n = 11), exercising regularly or irregularly less than 2h were examined. Heart rate monitor 220 (heart rate)-age formula wits used to evaluate the maximal exercising test during the procedure. Serum Se was analyzed by atomic absorption spectrophotometry. The difference between groups before and after the exercise was tested by Wilcoxon test, and the difference varying in the groups was tested by Kruskal-Wallis variance analyse. The relation between heart rate and serum Se was tested by Sperman's rank correlation analyses. After maximal physical exercise, the serum selenium level decreased significantly compared with pre-exercise values (P < 0.05) in group I only. III group 1, maximal and pre-exercise heart rates as opposed to pre- and post-exercise serum Se level were negative correlated (P < 0.05). In conclusion, a nutrition regime rich in selenium may be beneficial for both athletes who exercise regularly and in patients with increasing oxidative stress. (C) 2004 Wiley-Liss. Inc.