Cardiorespiratory fitness, strength and speed in early and late mature youth soccer players - Janssens, M.; Philippaerts, R.; Stoops, F.; van Renterghem, B.; Craen, M.; Vrijens, J. (Book of abstracts of the 6th annual congress of the European College of Sport Science, 15th congress of the German Society of Sport Science. Cologne, 24-28 July 2001, 2001)