Variation of Oxidative Stress of Elite Football Players during Pre-Season and In-Season

Abstract

IntroductionThe elite players are constantly being exposed to multiple high physiological demands due to elevated number of training sessions and matches played in national and international competitions held several times during a week (King & Duffield, 2009); furthermore also psychological demands, in order to situation awareness, have the role in the performance (Di Tore, 2015). Thus, high physiological capacities are required to elite football players for sustaining the stress imposed by training and matches, that could influence the subsequent performance and recovery over the season (Silva et al., 2014). Other aspects are involved in non elite soccer players (Raiola, Tafuri, 2015ab) and for intermitting training (Gaetano, Rago, 2014), that is not previous in this study, such as the stretching effects (Altavilla, 2014) and the postural aptitude (Guetano et al., 2015). In this way, the monitoring of work-load, stress and recovery in football plays utmost importance for the planning and the periodization of training (Little & Williams, 2007) to determine whether an athlete is adapting to the training program, also minimizing the risk of injury, overreaching and illness. Particularly, when recovery is uncompleted, impairments in performance and risk of injury must be strongly considered (Brink et al., 2010; Nedelec et al., 2012). Thus, several reasons have been suggested for testing athlete's status during training in order to predict performance during competition (Buchheit, Simpson, Al Haddad, Bourdon, & Mendez-Villanueva, 2011; Svensson & Drust, 2005). Oxidative stress indicators have been suggested for monitoring physiological stress imposed by football matches (Andersson, Karlsen, Blomhoff, Raastad, & Kadi, 2009; Ascensao et al., 2008a). Oxidative stress has been defined as a disturbance in the balance between the production of reactive oxygen species (ROS) and antioxidant defences (Betteridge, 2000). Moreover, it is highly remarkable that ROS have a high potential as signalling molecules within the cells as they regulate and can switch (on/off) several mechanisms that are redoxdependent (Betteridge, 2000; Gutteridge, 1995; Gutteridge & Halliwell, 1992). Under normal physiological conditions, the quantity of ROS is in a fine-tuned equilibrium with the antioxidant defence system (Andersson et al., 2009). However, despite well-trained athletes present an higher antioxidant defence (Brites et al., 1999), significant imbalances may be resulted following a football match or an intense training session. In this context, An official match implies several acute physiological changes such as increased cardiac output and blood flow, increasing markers of oxidative stress in plasma (Andersson et al., 2009; Ascensao et al., 2008a; Krustrup et al., 2006). Increased oxidative stress induced by a match or training may compromise performance throughout a given period. Particularly, a competitive football match increases the levels of oxidative stress and delayed onset muscle soreness throughout the 72 h-recovery period (Ascensao et al., 2008a). Although the levels of ROS can be measured directly, they can also be estimated by measuring the by-products resulting from their interaction with other molecules in the cells with which they have biochemical affinity. These include markers of lipid peroxidation, deoxyribonucleic acid (DNA) and protein oxidation (Gutteridge & Halliwell, 1992). Understanding how oxidative stress respond throughout a given period of the season may provide useful information on training adaptations, particularly providing an understanding of exercise-induced fatigue and recovery over the season, in order to design efficient recovery strategies. In regarding, Brink et al. (2010) suggested the individual monitoring of stress and recovery to provide useful information to prevent football players from injuries and illnesses. Recently, J. R. Silva et al. (2014) showed significant changes in oxidative stress markers of physiological strain during the season in elite football players. …