This study showed that (1) the validity of high-end dGNSS systems allows meaningful investigations such as characterization of physical demands and effectiveness of safety measures in highly dynamic sports (2) physical demands were substantially different between GS, SG, and DH and (3) safety-related reduction of skiing speed might be most effectively achieved by increasing the ski–snow friction force in GS and SG. Therefore, the component of the ground reaction force in the direction of travel (ski–snow friction) and air drag force were computed. It was found that the applied methodology may not only be used to track physical demands and loads on athletes, but also to simultaneously investigate safety aspects, such as the effectiveness of speed control through increased air drag and ski–snow friction forces in the respective disciplines. Combining the dGNSS data with a digital terrain model of the snow surface and an air drag model, the magnitudes of ground reaction forces were computed. External forces were determined using WC forerunners carrying a differential global navigation satellite system (dGNSS). Therefore, this study applied new and accurate wearable sensor-based technology to determine the external forces acting on skiers during World Cup (WC) alpine skiing competitions in the disciplines of SG and DH and to compare these with those occurring in giant slalom (GS), for which previous research knowledge exists. However, due to methodological shortcomings in biomechanical research, data comprehensively describing the external forces that occur in alpine super-G (SG) and downhill (DH) are so far lacking. In order to establish appropriate physical conditioning regimes, which adequately prepare athletes for the loads and physical demands occurring in their sports and help reduce the risk of injury, sport-and/or discipline-specific knowledge of the external forces is needed. 5Group for Snowsports, WSL - Institute for Snow and Avalanche Research SLF, Davos, SwitzerlandĮxternal forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness.4Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.3Department of Sport Science and Kinesiology, University of Salzburg, Hallein, Austria.Moritz Health and Innovation Foundation, Center of Alpine Sports Biomechanics, St.
1Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.Matthias Gilgien 1,2 *, Josef Kröll 3, Jörg Spörri 3,4, Philip Crivelli 5 and Erich Müller 3
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