INTRODUCTION: During the flight phase, moment force, aerodynamic force and gravity act on the jumper. Therefore, an athlete must taken these mechanical factors into consideration when trying to maximize the effect of the aerodynamic force in the flight phase (Sasaki et al.1997). Body's surface area becomes larger in getting closer to the end of the jump motion on the platform. Therefore, jumpers cannot ignore aerodynamic force in trying to maximize the effect of jump motion (Sasaki et al., 2007). Especially in the flight phase, only the gravity and aerodynamic force affect a jumper. These forces depend on change of acceleration in any range of ski jumping. A jumper has to control his motion on all the situations. The purpose of this study was to reveal the influence of aerodynamic forces in the aerial area. METHOD: Four voluntary jumpers participated in this study during their training camp. They jumped with a small accelerometer, which is designed to be able to record the three dimensional accelerations and angular velocities. A mobile recorder was set on the jumper's back and was fixed by an elastic band. The data was recorded digitally with 200 Hz sampling frequency. The data in the local coordinate system had to be converted into the corresponding value in absolute coordinate system by using Euler's rotation matrix. The acceleration data were reconverted on the direction of the velocity vector from the absolute coordinate system. RESULTS AND DISCUSSION: The mean of flight distance between senior and junior jumpers revealed a great difference. The flight distance in each senior jumper was over the K-point (90 m), while the jump of junior jumpers did not reach the P point (70 m) in each jump. Aerodynamic force was calculated by subtracting the gravity from the total force. The drag force is a parallel factor to the velocity, while a lift force is a perpendicular factor to the velocity. Drag and lift forces during the flight phase are indicated by the Figure 1 and 2. The amplitudes of both the drag and lift forces converged around -200 N (see Fig. 1) and 200 N (see Fig. 2) approximately 0.5 seconds after the take-off. After the amplitude converged, drag and lift forces acted constantly to jumpers until beginning the motion for landing. The lift forces of junior jumpers progressively increased until touching down on the slope. On the other hand, lift forces of both senior jumpers were keeping almost same values until touching down. Two jumpers reached over the 90 m. CONCLUSIONS: The amplitude of both the drag and lift is almost the same approximately around 200 N.
© 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.