Computer animations of an actual high jump and of an altered jump produced using computer simulation. I produced the simulated jump by changing the motions of various body parts relative to each other in the air. The animations show that you can improve performance by changing the actions that the athlete makes in the air.
High Jump Animations
by Jesús Dapena
(email: dapena@iu.edu)
You can download two computer animations of high jumps from this page.
Computer simulation
The first animation shows an actual jump, analyzed using 3D filming methods. The second jump is an animation of an artificial jump generated using computer simulation. In this second jump, I kept the conditions in the run-up and takeoff the same as in the original jump, except that I had the takeoff occur slightly farther from the bar. So the height reached by the athlete’s center of mass was the same as in the original jump. And her angular momentum (or “rotary momentum”, a factor that plays an important role in determining the speed of rotation of the athlete) after takeoff was also the same as in the original jump.
But then, in the air, I made the knees flex very much as the athlete traveled up toward the bar. [By this, I don’t mean the adoption of a “fetus position”. What I mean is a body configuration in which the hip joints are hyperextended (i.e., the knees are kept low) while the legs flex at the knees as if the athlete wanted to kick the bar from below with her heels.] These changes made the athlete’s body more compact in the view along the bar. In turn, this made her somersault backward faster than in the original jump. I also improved her arch at the peak of the jump, and then made her un-arch with good timing. The result was a simulated jump that would have cleared a bar set much higher than in the original jump.
Videos
The files are in three formats, MOV, AVI, and M4V:
MOV format file of original jump
MOV format file of simulated jump
AVI format file of original jump
AVI format file of simulated jump
M4V format file of original jump
M4V format file of simulated jump
The MOV files have higher quality images.
NOTE: To facilitate the identification of the two animations, in the original jump the ground is shown in its true color (red), while in the simulated jump the ground is green.
You can play the videos directly in your browser. However, a better alternative is to download the files (right-click on the links above –preferably the MOV links– and select “Download Linked File As” or “Save Target As”). Then, open each file with QuickTime. If the movie does not loop (repeat over and over) when played, click on View-Loop. You can also use the right and left arrows of the keyboard to single-frame advance in order to see clearly the differences between the bar clearances of the original jump and of the simulated jump.
Caveat
The above example demonstrates that the result of a high jump can be improved through actions made in the air. However, I do not want to give you a false impression. Actions in the air are normally not the most important way to improve high jumping results. The actions of the athlete on the ground are generally more important than what the athlete does in the air. This is because actions in the run-up and takeoff phases determine key factors at the end of the takeoff phase. They are factors that can’t be changed after the athlete has left the ground. Those key factors are vertical velocity and angular momentum. Vertical velocity determines how high the center of mass will be at the peak of the jump. Angular momentum determines a lot of the athlete’s rotation in the air. So, yes, it’s good to optimize the athlete’s actions in the air, but it’s even more important to optimize what the athlete does while he/she is on the ground.