Redox status alterations during the competitive season in élite soccer players: focus on peripheral leukocyte-derived ROS

It is well known that exercise training can deeply affect redox homeostasis by enhancing antioxidant defenses. However, exhaustive exercise can induce excessive reactive oxygen species (ROS) production, leading to oxidative stress-related tissue injury and impaired muscle contractility. Hence, ROS represent important signaling molecules whose level has to be maintained to preserve normal cellular function, but which can also accumulate in response to repetitive muscle contraction. In fact, low levels of oxidants have been suggested to be essential for muscle contraction. Both aerobic and anaerobic exercise induce ROS production from several sources (mitochondria, NADPH oxidases and xanthine oxidases); however, the exact mechanisms underlying exercise-induced oxidative stress remain undefined. Professional athletes show a high risk for oxidative stress, and consequently muscle injury or decreased performance. Based on this background, we investigated leukocyte redox homeostasis alterations during the soccer season in élite soccer players. Overall blood redox status was investigated in twenty-seven male soccer players from primary division (Italian "Serie A" team) at four critical time points during the soccer season: T0: just before the first team training session; T1: at the beginning of the season; T2: in the middle of the season and T3: at the end of the season. The main markers of muscular damage (CK, myoglobin, LDH), assessed by standard routine methods, are significantly altered at the considered time points (T0 vs T1 P < 0.01). In peripheral leukocyte subpopulations, ROS production shows significant alterations at the considered time points during the soccer season, and strictly and significantly correlates with CK values at every considered time point. Our experimental data indicate that deep redox homeostasis alterations are evident during the soccer season in élite soccer players, and that oxidative stress can be easily monitored, besides using the standard plasma biochemical parameters, by leukocyte ROS production analysis.