In 1968, Dick Fosbury revolutionized the track and field event of high jumping when he won the 1968 gold medal in the Mexico City Olympics using a unique new method of jumping. The video shows Javier Sotomayor setting the world indoor record of almost eight feet (Budapest, 1989) using Fosbury’s technique, known in track and field circles as the “Fosbury flop.” The flop has completely supplanted all other high jumping techniques in the years since its introduction. But why is this technique so superior to earlier methods of jumping? It’s all in the physics.
Prior to 1968, jumpers used to attempt to clear the bar using a straddle technique in which they flung themselves sideways over the bar. To do this essentially the entire body has to be above the bar at the peak of the jump. In other words the center of gravity of a jumper has to pass above the bar. However, using the Fosbury flop your center of gravity actually passes underneath the bar! How can this be?
Well, look carefully at the video. As Sotomayor reaches the apex of his jump his legs are well below the level of the bar on one side and his head and upper torso are below the bar on the other. And by the time he lifts his legs above the bar his upper body is well below. At no time during the jump does his center of gravity actually reach the level of the bar. This is an obvious advantage over the straddle because in effect he does not have to jump as high. Viewed in terms of energy he uses less kinetic energy on takeoff because he needs less maximum potential energy to clear the bar compared to a straddle.
Leaping over a bar eight feet above the ground is an astonishing feat no matter the technique. Even using a trampoline, not too many people could come close!