1. National Institute of Physical Education of Catalonia (INEFC), University of Barcelona (UB), Barcelona, Spain
2. Grup d’Investigació Social i Educativa de l’Activitat Física i de l’Esport (GISEAFE), INEFC, University of Barcelona (UB), Barcelona, Spain
3. Development Department, International Tennis Federation, London, UK
4. School of Sport and Exercise Sciences, University of Kent, Canterbury, UK