Determining the load for resisted sprint training with sled towing in soccer players. A pilot study - Cánovas, J. F.; Martinez-Valencia, M. A.; Marin-Pagán, C.; Gonzalez-Zaragoza, M.; Alcaraz, P. E. (17th Annual Congress of the European College of Sport Science (ECSS), Bruges, 4. -7. July 2012, 2012)