The purpose of this study was to identify the characteristics of the ground reaction force (GRF) production within the elite ski jumpers. We measured the GRF exerted perpendicular to the take-off platform during take-off motion in the actual ski jumping situation. Twelve ski jumpers of the Japanese national ski team took part in this study. We calculated the following variables; the maximum force (Fmax1) during 10-6.2 m before the take-off edge and the maximum force (Fmax2) during 6.2-0 m before the edge. Then we calculated a quotient of Fmax2 to Fmax1 (F 2/F 1). We calculated the maximum value of vertical velocity of the center of gravity (Vmax). We also calculated the minimal value of vertical displacement of the center of gravity (DCGmin) and its time duration from the edge (T 1).
Fmax1, Fmax2 and F 2/F 1 had no significant correlation with Vmax. These results would suggest that the elite jumpers could attain almost the same velocity by their own take-off style. F 2/F 1 was positively correlated with T 1 and negatively correlated with DCGmin respectively. These results suggest that the force produced on the latter part of the take-off platform such as Fmax2 had some influence on the counter movement and the timing of beginning of the take-off movement.
