INTRODUCTION: Technique plays an important role in performance in alpine ski racing. Knowledge of technique is primarily anchored in the philosophies developed by experienced coaches and athletes. In recent years, a philosophy emphasizing a short and direct trajectory in slalom and giant slalom has gained popularity in coaching circles (Gartner, 2007). The purpose of this investigation was to evaluate this 'direct line" philosophy by quantifying the center of mass (COM) trajectory length and determining its relationship to performance for a given Situation in slalom. METHODS: The performances of six male members of the Norwegian Europa Cup team were analyzed during a race Simulation in slalom in April, 2006. Skier 3-D positions were determined from 4 panning cameras and calibration control points distributed near the course (Nachbauer et al, 1996). A global coordinate System for the 2 analyzed turns was defined with the X-axis directed down the hill and parallel to the average direction of the course, the Y-axis directed across the hill, and the Z-axis normal to the plane of the snow surface. Total COM distance traveled (TTOT), distance traveled in the Y-dimension (TY), and distance traveled in the Z-dimension (T2) were quantified for each athlete's fastest run. To evaluate their relationship to performance, partial correlation coefficients between COM travel (TTOT. TY, TZ) and performance time - while controlling for entrance velocity - were calculated. RESULTS: Mean trajectory distance for the two turns was approximately 25 m (Table 1). In all three dimensions, a shorter trajectory tended to be advantageous. However, one of the fastest athletes skied a longer trajectory, possibly allowing him to ski more carved turns with less friction. Supej et. al. (2003) found that snow deterioration plays a role in determining the skier"s trajectory. Since this athlete had a later starting number, it may be that a rounder line was selected to avoid damaged snow. The relationship between TZ and performance is of great interest and may correspond to the importance coaches place in so-called "snow contact." CONCLUSION: Although there was a trend towards shorter trajectories being advantageous, this study demonstrates that there can be exceptions to the "direct line" philosophy. Athletes may need to be able to adapt their trajectory length to external factors such as degenerating snow conditions. Further investigation into the role of T2 and the skier's vertical dynamics is indicated.
© Copyright 2007 4th International Congress on Science and Skiing. Published by University of Salzburg. All rights reserved.