The mechanics of the curved approach in high jumping

In high jumping, the Fosbury Flop technique is currently used by all elite high jumpers throughout the world. The technique involves an acrobatic bar clearance at the end of a curved approach run. Initially the curved approach was considered to be no more than an idiosyncrasy of Dick Fosbury. However, the curved approach remains the preferred approach among elite jumpers, and therefore can be expected to be advantageous in high jumping. Speculations on the possible advantages of the curved approach have been made, but most are not based on experimental data and all lack convincing mechanical explanations. In order to understand the contribution of the curved approach to high jumping technique, the characteristics of the approach needed to be examined. Analysis of the 15 m approach phase of the high jump posed a. challenge in terms of obtaining the appropriate size of image and field of view. A number of image analysis systems were evaluated before one with the appropriate accuracy was selected. A total of 15 jumps performed by two elite high jumpers in two competitions were analysed. It was found that the curve through the foot placements tightened towards the end of the approach. Concurrently the inward body tilt towards the centre of the curve decreased resulting in an angular velocity about the frontal axis of the body. This suggested that the curved approach was used to provide the somersault rotation over the bar. In order to test this hypothesis a computer simulation model of the approach phase was developed and evaluated using the data from the image analyses. The model was used to explain the mechanics underlying the curved approach in the Fosbury Flop. It was found that tightening of the foot placement curve towards the end of the approach generated somersault rotation and also contributed to twist rotation at takeoff.