1 Journal of Human Movement Studies, 2005, 48: 109-123. Architectural characteristics of vastus lateralis muscle and jump performance in young men L. M. Alegre, D. Aznar, T. Delgado, F. Jiménez, X. Aguado Facultad de Ciencias del Deporte, Universidad de Castilla-La Mancha. Toledo, Spain. Correspondence: Luis M. Alegre Facultad de Ciencias del Deporte, Universidad de Castilla-La Mancha Campus tecnológico. Antigua Fábrica de Armas Avda. Carlos III, s/n 45071 Toledo Spain Tel: +34 925 268800 (Extension-5520) Fax: +34 925 268846 E-mail: luis.alegre@uclm.es Abbreviations: CMJ: counter-movement jump SJ: squat jump Keywords: biomechanics muscle architecture jump tests ultrasonography pennation angle fascicle length Summary Muscle architecture describes the geometric design of a muscle. It will have a great influence in the force generating capacity and the shortening velocity of skeletal muscle. The purpose of the present study was to investigate the relationship between architectural characteristics of one leg muscle and jump performance in a group of physical education students. Ten male students of physical education volunteered for the study. They were tested for their dynamic explosive force by asking them to perform jump tests on a force platform. Skeletal muscle architecture of vastus lateralis was visualized using ultrasonography and their body composition was evaluated. Isolated muscle thickness and fascicle pennation angle of vastus lateralis were measured in vivo, and fascicle length was estimated, using the ultrasonographer.