INTRODUCTION: The definition of meaningful biomechanical models of alpine skiing technique turns out to be a much more difficult challenge than the parametric modelling frequently used in other sports. Nevertheless, the kinematic and kinetic motion description during high level competitions can provide fundamental information towards the quantitative evaluation of the biomechanical constrains which influence the performances. Provided the limited amount of studies reporting movement kinematics during ski competitions, we focused our work on collecting three-dimensional kinematics data on athletes during a World Cup Slalom race. METHOD: The data were collected during the men's slalom World Cup Finals, (16.3.2008-Bormio). Two digital camcorders (SONY- 50 Hz) were located on both sides of the slope and acquired the skier's motion throughout four gates in the middle part of the race. A dedicated software for video analysis, allowing the operators to freely panning, tilting and zooming, was used to ensure the largest possible working volume (Baroni, 1998). The system calibration was performed by means of the DLT method, with a minimum of six control points in a three dimensional distribution. The 3-D localization of the control points (gate poles, nets Supports, etc.) was obtained by means of a geodetic theodolite. A 13 segment model was applied in order to estimate the position of skiers center of gravity (CG) Instant CG velocity, joint's angles functions and the inclination angles of legs with respect to average slope plane (25°) were calculated. Estimation of centrifugal acceleration was computed by combining instant curvature radius and CG velocity-time functions. RESULTS: Data acquired for best ranking skiers are presented in this work. Fig. 1 shows the typical paths of CG and heels on the average slope plane. Results show that each skier performed the four analyzed turns in less than 3.1 seconds. At the phase of "criange of the edges" of each turn, the CG average vertical displacement was 30.2 cm, with an average vertical velocity of 1.01 m/s. DISCUSSION and CONCLUSION: According to previous works (Pozzo, 2005, Raschner, 1997) the knee joint angle reached a minimum value of 70° and a maximum of 150°. The kinematics of additional biomechanical parameters is discussed with reference to the potential biomechanical significance for the optimization of the movement performance.
© 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.