Explosive force in football association: effects of competition and field location

Explosive force was assessed through squat jump (SJ), counter movement jump (CMJ), and elastic index (IE) in 21 South American football players at the beginning and the end of a six-month competitive period. Jumps were accomplished on a force platform and the data obtained were grouped according to: time, beginning and end of competitive period, and field location of the players (defenders, midfielders and attackers). T-test and Kruskal-Wallis analysis for the differences between positions were used to analyse its influence, as well as that of the competition, on the variables considered. The association between the CMJ and SJ was analysed by Pearson product- moment. The values found for SJ, CMJ and IE were below international standards. The IE showed that explosive force is significantly affected by the competitive period for those field positions implying high intensity activities during the match. The correlations suggest that differences exist on the factors that determine the significant changes for midfielders and forwards. It is concluded that the application of exercises that imply an action of the type stretch-shortening cycle (SSC) during the highly intensive competitive period could contribute to optimize the performance of the players.