INTRODUCTION: Nowadays, giant slalom races are won by hundredths of a second. Difference between the athletes on the podium is generally less than 0.5 s, which represent less than 0.5% on a 2 min race. Very small details make the difference and it is important to understand where, when and how the top athletes make the difference. Energy principles in slalom have already been explored (Kugovnik 2005, Reid 2009), but giant slalom biomechanics still needed to be explored. The aim of this project was to develop a system adapted to giant slalom analysis and to figure out the possibility for an athlete to increase his energy, and therefore improve his time, through active movements during turns. METHOD: 7 EC and FIS racers participated in the study. They were wearing a white suit equipped with black markers. The athletes performed 2 runs in a Giant Slalom. Six panning and tilting cameras (48Hz, 1Mo resolution) were positioned around the slope. A software especially developed recorded the frames directly on the computer's RAM memory. Dedicated boxes performed GPS based wireless synchronization with high accuracy for all the cameras. 43 poles with 3 markers each were set up around the run to calibrate the camera orientation. All the references points where measured with a theodolite. The 3D model reconstruction was processed using SIMI motion. The skier Center of Gravity was calculated with the Hanavan method. An energy balance using the potential, kinetic and dissipated energy allowed the calculation of the active energy of the skier. RESULTS: The system allows the visualization and the recording of a 20s run in a 2 Go RAM before writing data on the hard drive. An accuracy of 2cm for each reconstructed point is reached. ' The CoG position accuracy is also better than the individual point accuracy. The energy balance shows the same template for all the athletes but the curve tends to be higher for Top level racers. DISCUSSION: The decrease of the active energy during the first half of the turn implies absorption of energy by the skier. During the second half of the tum, the skier increases his total energy. Vibrations of the skis-skier system can also be a source of energy dissipation and need to be quantified. CONCLUSION: This study proposed an experimental set up for giant slalom analysis. Energy balance of high level racers was also performed and the absorption and restitution of energy still need further investigation.
© 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.