INTRODUCTION: While in the past the fastest turn was thought to be a purely carved turn with the smallest energy dissipation possible, nowadays tighter arcs and drifted turns can be observed in top level ski racing. These kinds of line characteristics result in higher energy dissipation during a direction change and higher velocity gains during the transition. Recent studies in slalom (Reid et al. 2007, Supej et al. 2010) mainly investigated the influence of different parameters on energy dissipation as a predictor of performance. In Giant Slalom (GS) however the distance between gates is greater and the potential for velocity gains during the transition is higher. The aim of this study was to show how a Top World Class Athlete intuitively deals with the individual and situational compromise of maximizing speed and minimizing energy losses on a typical GS section with conditions similar to world cup. METHOD: For that purpose a full 3D kinematic field measurement, using a system of 5 panned, tilted and zoomed cameras (50 Hz) time synchronized by a gen-lock signal, was carried out. A body segment model and geodetic measured reference points were manually digitized in each frame. The 3D position data were then calculated in PEAK MOTUS using a Panning Algorithm. Due to the fact that this measurement method is limited by its time-consuming data evaluation, we decided to perform a case study in order to increase the trials per condition. A Top World Class Athlete performed in total 12 runs at two different course settings (26 m vertical, 10 m & 12 m horizontal). At each course setting the faster turns were compared to slower turns. For all kinematic parameters the beginning (a) and end (b) of the turn were determined by the crossing points of the center of mass (COM) line and the ski line projected to the slope plane (x,y-plane), whereas the x-axis was the direction of the fall line. RESULTS and DISCUSSION: Trials with faster and slower sector times differed mainly in the x,y-position of the beginning and the end of the turn, as well as in the placement of the COM line in relation to the gate and the x-axis. These differences in line characteristics are also reflected in other calculated parameters, such as skid angle, edge angle, fore-aft position, turn radius, traverse angle, speed and energy dissipation. The differences in these parameters are more pronounced at the tighter course setting. There was no indication that a shorter path length is advantageous. Fast turns were initiated earlier followed by a patient "forward gliding". As soon as the necessary horizontal distance (y) has been reached ("invested"), a sharp COM direction change was performed in order to finish the turn as quickly as possible regarding the vertical distance (x). Subsequently a longer and more direct transition led to higher speed gains. CONCLUSION: It is not the shortest line that results in the best performance. It is rather the timing and placement of the line, which is important for the compromise of gaining and losing speed. As methodological consequence, training of the intuitive anticipation mechanisms in terms of line / timing aspects should be a main focus for technical / tactical training.
© Copyright 2010 Book of Abstracts. 5th International Congress on Science and Skiing, Dec. 14 - 19, 2010, St. Christoph am Arlberg. Veröffentlicht von University of Salzburg, Interfakultärer Fachbereich Sport- und Bewegungswissenschaft/USI. Alle Rechte vorbehalten.