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Evaluation of the Blood Antioxidant Capacity in Two Selected Phases of the Training Cycle in Professional Soccer Players The aim of this study was to evaluate the effects of a regular pre-season training on the aerobic performance and the blood antioxidant defense capacity in soccer players from the Polish Premier League club (n=19) and IVth League team (n=15). The players participated in an incremental treadmill running exercise to volitional fatigue twice (i.e., at the beginning (Trial A) and the end (Trial B) of the pre-season spring training). In venous blood samples, taken at rest and 3 min post-test, the activities of antioxidant enzymes (SOD, GSH-Px, CAT, GR) and concentrations of non-enzymatic antioxidants (GSH, tocopherols, retinol, uric acid) and malondialdehyde as a lipid peroxidation biomarker were measured. With the aim of between-group comparisons and possible conclusions on training-induced changes in the capacity of the blood antioxidant defense, the POTAX index was calculated as a sum of standardized activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants. The results of the present study indicate that the players from the Premier League club were characterized by only slightly higher maximal oxygen uptake rates, the differences compared to IVth League team, as assessed in both trials, were statistically insignificant. Participation in the pre-season training resulted in a moderate improvement of aerobic performance, although only a few players were characterized by VO2max comparable to the international-class elite performers. No distinct differences were observed in the level of aerobic performance between higher- and lower-classified players. Pre-season training led to an improvement in the global blood antioxidant capacity expressed in terms of POTAOX indices, although the changes in the activities and concentrations of individual components of the antioxidant system were less pronounced. Training-induced level of antioxidant conditioning was higher among the Premier League players, which may be related to differences in the training schedule and nutritional preparation of the athletes.

Rapid increase in the prevalence of obesity among children and adolescents has become a major worldwide health issue. Several large epidemiological studies have demonstrated that childhood and adolescent obesity is a significant independent predictor of metabolic disorders, such as hypertension, dyslipidemia and insulin resistance, which have a major impact on the premature development of atherosclerosis and cardiovascular morbidity and mortality in adulthood (Bibbins-Domingo et al., 2007; Dietz & Robinson, 2005; Franks et al., 2010). The cluster of metabolic disorders including abdominal obesity, insulin resistance, dyslipidemia and elevated blood pressure has been defined as metabolic syndrome (Alberti et al., 2006; Aggoun, 2007, Han & Lean, 2006). It is now generally accepted that overweight or obese children and adolescents are at increased risk for some or all of the metabolic syndrome (MS) features (Carnethon et al., 2004; Franks et al., 2010; Magnussen et al., 2010; Zimmet et al., 2007). The data from the Third National Health and Nutrition Examination Survey (NHANESIII, 1988-1994) have demonstrated that about 4 % of the whole population and almost 30% of the overweight or obese 12 to 19-y-old adolescents met the criteria of MS (Cook et al., 2003). The early occurrence of the MS in childhood and at the pubertal age was also found to have a major impact on the development of atherosclerosis, a life-time risk of cardiovascular disease (Aggoun, 2007), and an increased rate of premature death (Franks et al., 2010; Nieto, 1992). Excessive body weight in childhood and adolescence is considered a strong predictor of adult obesity (Wang et al. 2008) and obesity-related health consequences including diabetes and heart disease (Carnethon et al., 2004; Must et al., 1992; Morrison et al. 2007) regardless of whether the parents were obese. Notably, parental obesity was found to double the risk of being obese in adulthood (Shengxu et al., 2003; Whitaker et al., 1997).