vault3rb0y wrote:The goal is not to compress the pole. The goal is to move the pole the vertical.
As Kirk points out, the goal is to vault high, achieve max height. Moving the pole to vertical certainly helps this. Certainly. But I feel vault3rb0y is moving into the area of intent versus the actual. In modern vaulting we know that PB vaulters don't concern themselves with achieving pole bend or compression, yet their poles still bend and compress from the forces on them. So we still need to think about compressing levers. I would think that since we are dealing with a double pendulum system everyone here would understand pendulums and rotating lever properties, but apparently there is still some fog about the subject...
Short pendulums/levers rotate faster if they contain the same amount of energy. Since most pendulums work with gravity as the accelerating force from a potential energy starting point, the longer the pendulum the slower it moves. You might want to think about a figure skater who starts a slow spin with their arms and legs extended and by pulling in their arms and legs spins faster. Now, at least from one perspective the vault is the manipulation of two pendulums, the pole and the vaulter, to achieve max effect.
Compressing the pole, shortening its chord, makes it move forward faster, or rotate faster, and thus helps move it to the vertical. It's just physics that we can witness and see in many objects and has been studied and documented for centuries. It's science. The force on it and its rate of compression are important. Also, because its an elastic lever, it stores and returns energy. Both are good things that have lead to the boom of WR heights since the advent of the flex pole.
Some also seem aware that its best if the vaulter presents a long lever as soon as possible in the swing. Why? Well one reason is that they are intuitively aware from years of either vaulting or coaching that if the vaulter shortens their swing, pulls up their take off leg or pulls with the arms, it kills the vault? Why? Well I've been trying to explain why. They lose compressive force from gravity. The pole doesn't shorten as much, doesn't store as much energy, doesn't rotate as much to the vertical, and they stall out. Much of my thoughts, as the depraved free thinker that I am, came from watching new vaulters fail vaults for this reason. Then I would see a fairly good HS vaulter and think, "IF they could only stay back and down on that swing for a bit longer, they could use a bigger pole/higher handgrip, and vault higher." But as has been said here by Kirk most recently, that is often easier said than done. But still, logic and science gave me an intuitive lead that if the vaulter going forward and up too fast was bad, it was probably that staying back and down was good (which I explain with gravity vector analysis), and probably more efficient. And so not long after comes Lavillenie, in whose every action I see him working to stay back and down for as long as possible, and for which he seems to be one of the few guys that can get back out on top. How does he do it?
Well, we're back to pendulums and rotating levers. Think of him like a figure skater. Initially he's long. In his case he presses the CoM by lowering his right leg, lowering his CoM, which has the same effect of moving the weight of a metronome out on its lever. It slows hims down. This already starts the problem most find (myself included) with attempting this technique. It's hard to get out. What do you have to do? Well you have to at some point time a shortening of the lever, make yourself shorter, tuck. The problem with most tuck vaulters as I see it is that they start too late and past the time when they should tuck. If you watch Lavillenie, his tuck happens early, at least in his angular rotational attitude. And its a very dynamic tuck. He changes shape fast, almost violently, which radically changes his rotational speed. Think again of a spinning figure skater. Even for them they usually speed adjust at manageable rates for if they would just all the sudden whip their arms and legs in it causes a greater chance to lose balance. Lavillenie's timing and control are almost superhuman. He gets out on top and wastes no time in extending over the pole. He's better at this than anyone has ever been. Also, by shortening himself as a lever, it gives him a leverage advantage about the shoulders. That is, he can add more efficiently to his rotational speed through muscular activity.
Take Off and Continuity
Really, I don't know. Information says he's moved to a "free take off". In some sense it matters not to me. The vaulters "hanging" angle which determines the gravity vector resolution can be paired with a free take off. Does he come off low, high? I don't know. I just know the ideas aren't incompatible. One of the things I keep trying to point out was that in the PB model they were very interested in not having the CoM thrown forward under pole braking. This was a great leap forward according to my analysis because as the CoM goes forward, as the angular relation to the top hand progresses, the vaulter loses compressive force. Lavillenie extends the process, actively.
And progresses actively through the entire vault. I see no delays. The take off is active. He activates himself into the pole with arm use, causing action/reaction with himself and the pole. The right leg doesn't pause in movement.
And one last thing. In another thread Tim makes a comment about the take off/trail leg.
A double leg swing lowers the vaulter's COM. That factor outweighs having a shorter trail leg unless the trail leg is very long with a very powerful swing, in which case it is a wash, in my experience. I jumped just as high both ways, and I have seen so many high jumps with a double leg swing and without one that I regard it as a style difference and not a fundamental element of the vault.
This reinforces my silly glee at watching Lazero Borges. That take off/trail leg action is marvelous. That he can use it so far behind him is him ever moving his CoM back during the vault while you can watch him press and repress the lead arm. Then he swings that leg back forcefully down. And so where we might characterize Lavillenie as a down and back vaulter, Borges is more back and down. Oh, but that spicy Latin run up..http://en.wikipedia.org/wiki/Pendulum
In particular note, "Animation of a pendulum showing the velocity and acceleration vectors". Gravity is along the perpendicular line, and note the changing forces
which the activity of the vaulter can manipulate...