486 International Journal of Sport Nutrition and Exercise Metabolism, 2012, 22, 486 -496 © 2012 Human Kinetics, Inc. Jówko, Sacharuk, M. Charmas, and R. Charmas are with the Faculty of Physical Education and Sport in Biala Podlaska, University of Physical Education, Warsaw, Poland. Balasinska, Wilczak, and Ostaszewski are with the Faculty of Veterinary Medicine, Warsaw Agricultural University, Warsaw, Poland. Effect of a Single Dose of Green Tea Polyphenols on the Blood Markers of Exercise-Induced Oxidative Stress in Soccer Players Ewa Jówko, Jaroslaw Sacharuk, Bozena Balasinska, Jacek Wilczak, Malgorzata Charmas, Piotr Ostaszewski, and Robert Charmas Purpose: To evaluate the effect of acute ingestion of green tea polyphenols (GTP) on blood markers of oxi- dative stress and muscle damage in soccer players exposed to intense exercise. Methods: This randomized, double-blinded study was conducted on 16 players during a general preparation period, when all athletes participated in a strength-training program focused on the development of strength endurance. After inges- tion of a single dose of GTP (640 mg) or placebo, all athletes performed an intense muscle-endurance test consisting of 3 sets of 2 strength exercises (bench press, back squat) performed to exhaustion, with a load at 60% 1-repetition maximum and 1-min rests between sets. Blood samples were collected preexercise, 5 min after the muscle-endurance test, and after 24 hr of recovery. Blood plasma was analyzed for the concentrations of thiobarbituric acid–reacting substances (TBARS), uric acid (UA), total catechins, total antioxidant status (TAS), and activity of creatine kinase (CK); at the same time, erythrocytes were assayed for the activity of superoxide dismutase (SOD). Results: In both groups, plasma TBARS, UA, and TAS increased signifcantly postexercise and remained elevated after a 24-hr recovery period. SOD activity in erythrocytes did not change signifcantly in response to the muscle-endurance test, whereas in both groups plasma CK activity increased signifcantly after 24 hr of recovery. Acute intake of GTP cased a slight but signifcant increase in total plasma catechins. However, GTP was found not to exert a signifcant effect on measured parameters. Conclusions: Acute ingestion of GTP (640 mg) does not attenuate exercise-induced oxidative stress and muscle damage. Keywords: catechins, antioxidants, oxidation-reduction balance The generation of reactive oxygen species (ROS) is an inevitable consequence of normal cellular metabolism. The body defends itself against their detrimental activity by means of the antioxidant defense system, the objec- tive of which is to render ROS harmless. The system is composed of antioxidant enzymes including, among others, superoxide dismutase (SOD) and glutathione peroxidase, as well as nonenzymatic antioxidants includ- ing glutathione, coenzyme Q 10 , uric acid (UA), vitamins, and polyphenols (Lamprecht, Greilberger, Schwaberger, Hofmann, & Oettl, 2008). Under conditions of intensifed ROS production, the antioxidant defense system may prove ineffcient, which in turn leads to oxidative stress, a state induced by the imbalance between antioxidative and pro-oxidative processes (Fisher-Wellman & Bloomer, 2009). Strenuous physical exercise is one of the factors alleged to induce oxidative stress. Under conditions of exercise-induced oxidative stress, increased oxidation of cell constituents—DNA, lipids, and proteins—has been observed (Banerjee, Mandal, Chanda, & Chakraborti, 2003). The oxidative stress induced by acute physical exercise may lead to aerobic damage of muscle tissue, consequently intensifying muscle soreness and diminish- ing exercise performance (Lamprecht et al., 2008). It is suggested that lipids are more sensitive to oxi- dative damage than proteins are (Morillas-Ruiz, Villegas Garcia, Lopez, Vidal-Guevara, & Zafrilla, 2006). ROS release causes lipid peroxidation of polyunsaturated fatty acids in biological membranes and blood. Malondialde- hyde, a by-product of lipid peroxide, and thiobarbituric acid reactive substances (TBARS; indirect assay used to measure aldehyde products, primarily malondialdehyde, formed via decomposition of lipid hydroperoxides) have been the most frequently used markers of oxida- tive tissue damage during exercise (Fisher-Wellman & Bloomer, 2009). In fact, increased oxidative-stress biomarkers have been observed not only after aerobic exercise (exhaustive long-distance cycling and running) but also after anaerobic exercise (supramaximal sprints or strength-type exercises; Bloomer & Goldfarb, 2004; García-López et al., 2007). It is common knowledge that intensive anaerobic exercise induces oxidative stress, www.IJSNEM-Journal.com ORIGINAL RESEARCH