Variation of oxidative stress of elite football players during pre-season and in-season

The 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. The aim is to assess oxidative stress variation throughout pre-season and the first half of the season by comparing month-by-month free radicals. Secondly, we aimed to compare overall pre-oxidative stress to in season one. The methods is experimental. Blood samples were obtained per month from twenty-three elite football players, during seven-months season (2 months pre-season and five-months in-season). The results show a large negative correlation was observed between July and August and between November and December (p=0.02; r=-0.54; p=0.03; r=-0.45 respectively). Significant interaction was observed in ROS over the whole analysed period (p<0.01; ž2=0.19) in function of the monthly analysis. Monthly ROS increased (p<0.05) from November to October, and then decreased (p<0.05) from October to November. In conclusion the Oxidative stress vary over the season. Thus, a certain risk of non-contact injury and illness must be considered at a given seasonal stage, particularly in September, when competitive season is beginning. Further research may relate training load to oxidative stress over a given period to better explain the present results.