A COMPARISON BETWEEN THE KINEMATIC CHARACTERISTICS OF THE TRANSITION PHASE OF SKI-JUMPING ON JUMPING HILLS WITH DIFFERENT CRITICAL POINTS

  • M. Janura
  • F. Vaverka
  • M. Elfmark

Abstract

The jumping hill construction is one of the major external factors which influence the ski-jump. The increase in the jumper's velocity reduces the time for the mainparts of the ski-jump. It is necessary to determine the influence of these changes on the transition phase in the ski-jump. The transition phase is the section from the edge of the hill to the beginning of the flight phase. This part is determined by many factors which occur during the takeoff. The magnitude of the aerodynamic forces increases with the high velocity. Therefore, for the quick implementation of the transition phase, the rotation of the ski-jumper has to increase. We suppose, that the inter individual differences between various performance levels of jumpers will increase. The purpose of this study was to find relationships between the kinematic characteristics of the transition phase on jumping hills with different constructional characteristics and to determine the degree to which jumpers at various skill levels are able to manipulate the technique. The study was carried out at the events held on the jumping hills with different critical points: - GP Frenstat pod Radhostem (K=90) – Intersport tournee Innsbruck 1995 (K=109) - World Championship in the ski flight Planica 1994 (K=185).The 2-D analyses were implemented using the System of Kinematic Analysis of Ski-jumping, which was presented on the XI1 International Symposium of Sport Biomechanics in Budapest. This system allows us to find the basic angle, length and velocity parameters for the transition phase of the ski jump. The sets of competitors in the 1st round (n=50-80) were divided -into three groups (n=12-15,B-best, M-middle, Glow) according to the length of jump. The statistical analyses were using the statistic package Statgraphics.
Section
Coaching and Sports Activities