1 Swiss Federal Institute of Sport Magglingen, SWITZERLAND Swiss Federal Institute of Sport Magglingen, SWITZERLAND National School of Mountain Sports National Ski-Nordic Centre Prémanon, FRANCE Swiss Federal Institute of Sport Magglingen, SWITZERLAND Institute of Sport Sciences University of Lausanne, SWITZERLAND Departmental Section of Physical Education and Sports University of Alicante, SPAIN Swiss Federal Institute of Sport Magglingen, SWITZERLAND Swiss Laboratory for Doping Analyses Center Hospitalier Universitaire Vaudois and University of Lausanne, SWITZERLAND Institute of Sport Sciences University of Lausanne, SWITZERLAND.