A kinematic analysis of the V-style ski jump

Abstract

The purpose of the study was to identify, describe, and quantify selected kinematic variables associated with the successful performance of the ski jump. Secondly, this study attempted to determine the statistical contribution of specific kinematic variables at takeoff and the beginning of the transition phase for the distance jumped. The subjects for this investigation were 60 highly skilled competitors participating in 1994 World Cup K- 120 event. The top twenty eight jumpers were selected from the first and second jump of the official training day for the K-120 event. Data were collected using two Panasonic video cameras, one was set up to record the take-off phase, another was set to record the transition phase, equipped with a high speed shutter. Data for the distance jumped were collected from the records for the two official training jumps held the first day of official competition. The 2D Peak Performance Video Analysis System was used to extract the horizontal and vertical coordinates for a 23 segment model. The centre of mass was calculated by a model which included 14 body segments. The data were smoothed using a second order Butterworth digital filter and processed to compute measures for determining linear displacements and velocities and angular displacements and angular velocity values. A computer program written by the author was used to process the data calculated for the variables selected specifically for analysis in this study. A correlation analysis was conducted to determine the existence and strength of any relationships between the selected variables and distance jumped. Seven variables were included in the multiple regression analyses. A full regression model provided the relative contribution of each predictor variable to the distance jumped. A stepwise regression model eliminated those variables which did not contribute significantly to the regression. Based on the results of the study, selected kinematic variables associated with the distance jumped were identified and described. The similarities and difference between the traditional style and the Vstyle of jumping were discussed. The results suggested that the jumpers who want to increase the distance should generate as large as possible in-run speed, create an optimal aerodynamic body position with forward lean movement, take a guicker drive segment extension to begin a forward lean rotation, at the same time keep and increase continually the velocity in the take-off phase, keep and increase the forward lean movement of body and extension in order to create an optimum aerodynamic body position during the transition phase.