INTRODUCTION: In ski jumping the take-oft is a key position within the entire movement. The execution of take-off, the jump intensity (vertical take-off velocity) and the angular momentum generated with the take-off have a direct impact on the take-in of the flight posture (Hildebrand, Drenk & Müller, 2008). Analyses of international best practise show a variety of different sport technical solutions regarding the varying deployment of the upper body. The execution of the take-off movement is an optimization process because it is impossible to maximize the vertical take-off velocity and minimize the air resistance simultaneously. Using computer simulations it was intended to simulate different motion sequences and to generate knowledge on optimal execution of take-off. METHOD: Using the simulation software JUMPICUS (Hermsdorf, Hildebrand, Hoffmann Müller, 2008), the constructed take-off movements with different angles of upper body were analysed systematically. JUMPICUS is a highly detailed biomechanical model for multi-body simulations in ski jumping which offers different methods of biomechanical analysis. By the method of inverse kinematics JUMPICUS evaluates joint angles as well as global position and orientation of the athlete over time. Based on these results ski jumping specific parameters (e.g. take-off velocity, take-off angular momentum, angles between body segments) are evaluated and can be compared with parameters of other variants or a given technical ideal. The basic aim for all simulated variants was to generate an angular momentum of 8 kgm2/s, together with the maximum vertical take-off velocity. For the construction of realistic take-off variants of acceleration, time and way, the maximum acceleration performance were considered. RESULTS AND DISCUSSION: Results show, that from an aerodynamical viewpoint the variations of take-offs with different angles of the upper body are almost equal. Therefore, the criteria result from the demands of the movement to achieve a sufficiently large angular momentum. Accordingly, an upper body angle of 20° at the take-off edge is optimal. Upper body angles of 13-26° at take-off have to be rated as equivalent, since the differences in the achievable take-off speed are so low that the maximum difference in distance is only 0.5 m. However it is necessary to realize different angles of lower body at the take-off edge depending on the angle of upper body (Müller, 2008). CONCLUSION: The simulation system JUMPICUS enabled us to identify optimal variants of the take-off, so that a large angular momentum and a high vertical take-off velocity can be achieved. For deeper insights it is necessary to execute dynamic simulations taking into account the external and internal forces as well as the involvement of the transition period.
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