Mechanics of rotation in the Fosbury-flop.

The mechanics of the rotations involved in the Fosbury-flop technique of high jumping were examined in the light of appropriate experimental data generated by use of a 3-dimensional cinematographical method. At the start of the take-off phage, the six subjects who used the Fosbury-flop had little angular momentum. Most of the angular momentum necessary for a proper bar clerance was not produced during the run-up, but during the take-off phase. A curved approach run appeared to favor the production of "somersaulting" angular momentum (the component of angular momentum which mainly contributes to lower the shoulders and lift the knees during the flight phase), as well as a greater vertical range of motion of the c.g. during the take-off phase. These conclusions give little support to the hypothesis that the main purpose of the curved run-up is to produce angular momentum during the run-up. On the other hand, they favor the hypothesis that the main purpose of the curved approach run is to make the athletes lean away from the bar. One athlete with particularly small "somersaluting" angular momentum made effective use of a hitch-kick motion to accomplish an effcicient bar clearance.