ABSTRACT
This chapter addresses the complex adjustments made by water ski jumpers to achieve timely contact with the ramp. Visual information is derived from the relative movement between the skier and the ramp. In order to understand the motor adjustments for proper timing, we propose to address the physical parameters involved in these motor adjustments and the possible informational basis on which they rest. The 2D trajectory of a point at water level between the feet of the skier was calculated from the films. Experts were found to demonstrate a narrow range of trajectories and their initial decision when to attack the jump is therefore critical for the development of maximal speed and hence ultimate performance. Utilizing the model we identified two potentially decisive parameters. The t? parameter seems to be more precise than F? but is only available 250 ms before impact.
