GRV: Lavillenie - From Stall Swing to World Record

[KirkB]

Sorry, when I browse to the 2nd page of google, I do find this definition from THE FREE DICTIONARY:

gravity vector [′grav·əd·ē ‚vek·tər]
(mechanics)
The force of gravity per unit mass at a given point.

But I still don't understand it in our PV context. I would like to read a scientific paper (like the one from Princeton) to understand this better. Which paper or wiki article should I read?

Kirk

[willrieffer]

The timing and rate of the swing angle and its necessary relation to the CoM and gravity vector and thus that vector's effect on the compression and chord shortening of the pole are crucial to the vault.

The more that the vaulter can delay the movement of the CoM forward, the more they can have the gravity vector resolve into the pole and not into swing momentum, the better the vault, that is, if they can do this and cover the pole. That is the trick.

The gravity force I'm talking about adds to the compression rate of the pole, based on the progression of the swing angle to the shortening the chord, and thus by shortening it adds to its rotational velocity.

There has been not one single reply that has addressed this directly in refutation. Not one.

Willrieffer, I THINK you make some good points here, but I'm not sure.

What exactly do you mean by "gravity vector"? That EXACT term has zero hits on google.

Unless your terminology is well-understood, your points are lost.

When googling "gravity vector", Wikipedia points to "scalar-tensor-vector gravity": http://en.wikipedia.org/wiki/Scalar%E2%80%93tensor%E2%80%93vector_gravity

Googling "gravity vector", also finds this scientific paper: http://www.hep.princeton.edu/~mcdonald/examples/vectorgravity.pdf

Which of these are you referring to? Or do you have a third definition, perhaps more specific to PV?

Thanks for any clarifications you can make about what you mean. If we can understand what you mean, then we can reply specifically to your point.

Kirk

First, thank you for this engagement Kirk.

http://en.wikipedia.org/wiki/Vector_field
http://en.wikipedia.org/wiki/Vector_calculus

Vector fields
Main article: Vector field

A vector field is an assignment of a vector to each point in a subset of space.[1] A vector field in the plane, for instance, can be visualized as a collection of arrows with a given magnitude and direction each attached to a point in the plane. Vector fields are often used to model, for example, the speed and direction of a moving fluid throughout space, or the strength and direction of some force, such as the magnetic or gravitational force, as it changes from point to point.

The gravity field is a vector field and it is by this we say that gravity has a vector. The gravity vector. In the vault we can generally say it points down. Since the vaulter rotates on the top hand you have a progression of the CoM around the point, and the gravity vector points down. If, for example, a vaulter is practicing on a high bar and they are not swinging, all of the force of gravity is through the CoM and then to the high bar. The bar is supporting all of the weight, or the acceleration of the gravity vector on the CoM and through the body to the bar. Now as the vaulter swings forward what happens is that you have to do a resolution of the gravity vector by analysis. The swing has energy, and one element that can slow the swing is the effect of gravity once the swing is past the vertical. This is what generally decelerates any swinging motion, say of a child swinging on a playground. The angle here really means something because as the vaulter swings forward in time the gravity vector has to be resolved into parts now since it has constant value g, and is now both decelerating the swing AND still pulling down on the vaulter. So as the vaulter swings forward from horizontal it does some of both. At first its still mostly on the pole, but as the vaulter is always swinging forward, it changes to more swing deceleration and less compression force. This is why the swing angle in time and rate are important. And the farther forward the CoM in time, the more gravity has to be resolved into deceleration and not into compression because the force of gravity does not change. But what changes is the vaulters relation to it. The deceleration moment of the swing has to be resolved first, it has to happen, and then whatever force is left is what acts on the pole. This is the scientific reasoning why one needs to "stay behind the pole". This also leads to why the double leg is an advantage and why one needs to consider extension of the lead arm.

Longer levers rotate slower. So anything the vaulter can do to lower the CoM then slows their swing. Think about this. Now over time they are losing less of the gravity vector force in time to swing deceleration. And since the force is constant where must it go? Into the pole, as energy and compression. It effects the compression rate. This shortens the chord faster in time and make the pole rotate faster and farther. Plus it puts more energy in the pole.

http://en.wikipedia.org/wiki/File:Oscil ... ndulum.gif

Look at the pendulum gif. The "a" vector is in direct relation to the gravity vector field, and it changes over time(at the point that the pendulum is vertical "a" completely opposes the gravity vector). And the force on the pivot point varies in relation. This is the same reason why a kid on a swing will, if they are swinging fast enough, when they get high up on the swing will "fly away" from the chain tension and show that at that point there is no counter force on the pivot point, which is where the chain attaches to the frame. For the vaulter this means there is no longer any compressive force on the pole from gravity. It also leads to the idea that the shorter the lever the vaulter makes to speed through the late swing when the pole is near or entering decompression has an advantage. Or, the tuck has an advantage if done at the right time(most IMHO are too late with it).

So look at what Lavillenie does. He drops the lead leg and works the trail leg back which both lowers and moves the CoM back in time. Lowering it makes him rotate slower. He actively does things to slow the rotation instead of letting gravity slow the swing! He loses less energy of the swing momentum to gravity and necessarily puts more energy in the pole and thus over time at this point at a faster rate. It is here I will address the lead arm. One cannot compare two vaulters lead arm action. One needs only to think about what happens when any vaulter with a bent arm extends it. By simple and pure geometry the arm gets longer and effects the swing angle as it pushes the shoulder back, followed by the torso, hips, and then CoM. When the arm extends it is longer. It has to push the system back. It is effective of the CoM in time. It pushes it back. And since it is back in time we have the same effect I have outlined above. There is less of the gravity vector resolved into the slowing the swing, and more goes into the pole. Now since Lavillenie has done all of this to "stall" his swing, he now has to radically tuck to speed his mid vault and cover the pole. This again is conservation of energy in rotation, the tuck is faster. Plus its easier to muscularly speed the tuck to cover. It's the difference between tucking to roll up to a high bar and levering up. That levering is harder to do and slower.

I'll ask you Kirk. Do you think these ideas have been countered or argumentatively addressed in any way by anyone here? I don't think so. And so we have again the point to PVStudent which is that I disagree with nothing he's posted or said here. The pics, the take off angles, etc. In fact I've agreed with almost all of it. The force of gravity is down on the pole despite what the left arm is doing. Good. Very good in my book. And yet he still has not addressed my point which I have made again and again and again, repeatedly. It is by this that I call his work peripheral to my point, and so even if it has value, and it does, it remains in my mind a "boondoggle" on my argument. It's barely pertinent, if at all. And so people look at what he is saying and, well, continue to be unable to focus on what I am saying and miss the point and veer off into other things.

Please feel free to ask any other questions.
And thanks for your time and interest.
Will

[KirkB]

Thanks for your explanation of the gravity vector. I haven't read your links thoroughly yet, so I'll have to read more before I truly understand (sorry for being so slow). But if I didn't understand what you meant by gravity vector then I'm sure that many others didn't understand either.

And there were some "leaps in logic" that you made that I didn't follow. Rather than being specific about them today, I will wait for others to ask about these. If no one asks in the next couple weeks, then I'll ask.

Thanks again for your explanation of the gravity vector.

I'll ask you Kirk. Do you think these ideas have been countered or argumentatively addressed in any way by anyone here?

I'm not going to get in the middle between you and PVS. You're both grown adults. You can duke it out directly with him. Just play nice.

From my perspective, I didn't understand what you meant by the gravity vector, so some of your arguments were lost on me. There's probably some other terms that you use that also distract from you main points. I'm only human, and as a human, I skim over details that I don't understand (or don't make sense to me). Maybe others have done the same with some of your points?

Kirk

[willrieffer]

Thanks for your explanation of the gravity vector. I haven't read your links thoroughly yet, so I'll have to read more before I truly understand (sorry for being so slow). But if I didn't understand what you meant by gravity vector then I'm sure that many others didn't understand either.

And there were some "leaps in logic" that you made that I didn't follow. Rather than being specific about them today, I will wait for others to ask about these. If no one asks in the next couple weeks, then I'll ask.

Thanks again for your explanation of the gravity vector.

I'll ask you Kirk. Do you think these ideas have been countered or argumentatively addressed in any way by anyone here?

I'm not going to get in the middle between you and PVS. You're both grown adults. You can duke it out directly with him. Just play nice.

From my perspective, I didn't understand what you meant by the gravity vector, so some of your arguments were lost on me. There's probably some other terms that you use that also distract from you main points. I'm only human, and as a human, I skim over details that I don't understand (or don't make sense to me). Maybe others have done the same with some of your points?

Kirk

It was unfair of me to ask you to be judge, sorry about that.

Some of the problem is that there are shortcuts in the nomenclature that were learned along the way in the progress of the engineering physics program. So a prof or grad student might say, "By the angle, calculate the resolution of the gravity vector into its component parts on the CoM". It is by this that I use such terms. I hope I have showed now how the term was generated even if it is not one that can be found easily on google.

Will

[PVDaddy]

You take the High Road and I'll take the low ♪ and I'll break the World Record befoooore you! ♪ (Even though I'm shorter and slower!)

Well done Will, well done my friend! You did not have to convince me, I saw it for myself, over a year ago. But thanks to your bright mind and mastery of Physics you have fully confirmed what natural instincts and a limited grasp of Physics (3 Physics courses) was telling me right along! Thank-You for fully describing what is meant by "The Gravity Vector" and how Lavellenie takes better advantage of it with his method as opposed to the PB method of pole vaulting. You have been more than adequately attempting to relay this concept to some hard headed individuals for over a year now! It must have been very frustrating for you that they would not even address it and keep wondering off into never land. You have displayed more patience and perseverance on one concept than anybody I know! If they won't recieve it now after your last post, they never will! and that's because A. They don't want to, because they didn't see it, much less think about it and therefore not receive the credit or B. They just don't have the mental capacity to recieve what is actually a very simple concept? I believe it's more likely the former. Can't have any pole vaulting nobodies telling the "biomechanics" and or "experts" what's up now can we? Enough of that, but many of you who have consistently dominated this board with your over-inflated egos had it coming!

Onto more constructive thought (never land sucks). Will, it makes obvious sense to me that if the goal is to keep your COG low for as early and as long as possible, the vaulter would want a much flatter take off than what has prior been considered ideal. In other words more focus on the horizontal component of the jump. This is actually ideal, as it preserves more of the runway energy as it is not loss to the braking effect on the plant foot and the transition (Biomechanical) loss from running to jumping hard in the verticle direction. I have previously mentioned this on many post. This is were PV Students Charts are indeed very helpful.! I refer the reader to his past post showing the still frame side by side comparison of Lavillenie and Bubka through take-off phase. download/file.php?id=1016. Notice how lavilennies drive knee is not nearly extended in the upward direction. Photos 1-5. Lavillenie is preserving more of the verticle component energy into his take-off and because his drive knee is not as extended he is taking better advantage of his gravity vector resulting in more pole compression and earlier rotation. Photo 5.

Will, it makes obvious sense to me that if the goal is to keep your COG low for as early and as long as possible, the vaulter would want to keep the bottom hand more extended by not allowing the elbow to bend as much and go back over the head. Lavillenie does this. Examine Photos 1-5 and compare them to Bukas. Notice how much further from the pole Lavillenies head is? He does not have to re-extended the bottm hand to lower his COG. He's already there! If your oing to do this you better have a very strong top hand grip and I think this was clearly shown by in his second attempt! Because he does not have to do this he also is not fighting the elemental rotation of the pole and Bubka is. This is a topic that is not being addressed! Notice how much more the pole is compressed but equally important how much more pole rotation Lavellenie has? Photo 10. The pole is compressing so fast and rotating so fast it actually results in a great twisting of lavillenies spine. He has to compensate for this by later pulling down on the pole and redirecting his swing (Hips) more to the right side of the pole. If you look at his video carefully you will notice he relaxes is thumb grip of his bottom hand and allows (even steers it some) the pole to rotate through his fingers. I believe This and steering his swing to the right assist in the natural elemental rotation of the pole.

As you say, because his swing is delayed, he must compensate with a very quick and efficient quasi double leg (frog like) tuck. I believe that because his pole has rotated much more than Bubkas he does not have to fight the pole as much and therefore is easily able to cover it at the top. Heck he even has to wait for it!

Do you agree that not only does he compress the pole more with his better use of the gravity vector, but, equally of importance, is able to cover it very quickly because he does a better job of not fighting the poles elemental rotation better than Bubka?

[KirkB]

You take the High Road and I'll take the low ♪ ...

I'm taking the high road.

This post was made by PVDaddy who is currently on your ignore list.

There, PVDaddy is back on my ignore list. Enough said.

Kirk

[willrieffer]

The angle of the pole in its rotation about the box and the angle of the vaulter to the gravity vector are not tied, but are independent. This is why you can use both the PB Model in take off and then post take off adopt a more Lavillenie/GRV swing orientation. This is where I note that while Dossevi practiced the gravity relative method, his take off was radically non PB and that evidence appears to show that Lavillenie has put the two together into the most efficient vault form in history.

The only other thing I can say here is that Lavillenie, well, there are training videos of him showing him working with a very flat take off that seems to somewhat disappear in his meet jumping. This may be left over from his pre PB take off days, and is something he's actively trying to correct.

It may be of use to some to watch the readily available long progression of Joe Dial who's progression from youth vaulter to world class is well documented in film and watch in particular the progression of his lead arm. In the beginning he is a very classic bent arm vaulter. And there is a bit of a relation between the scale of the vault and the front arm. For youth vaulters at low heights the vault happens so fast that its hard to press and cover. Dial even makes mention of his progression to having to extend the arm as he goes up in grip height and so on through time. I also believe that I see even Bubka become more active with the front arm over time on which I would theorize that it was due to a necessary response to some loss of foot speed over time. Also, it is worthwhile to look at Tradenkov versus Bubka as the slower man had to work harder to stay back and work the gravity energy into the pole and was then forced to use more of a tuck to get out and cover.

PVStudent himself has made note of the difference between attack in shorter and taller vaulters and here we are talking about Lavillenie and Dial, noted shorter vaulters. I have before said that there are possible high path and low path efficiency maximums for vaulters. But the analysis of this, again, would take more than a static analysis, but one that used vector calculus over time. And it would take tools I don't have access to.

Will

[PVDaddy]

Do you agree that Lavellenie does a better job of not fighting the poles elemental rotation better than Bubka?

[PVDaddy]

Evidently my statement about the Experts with the overinflated ego's must have applied to Kirk (I didn't address anyone in Particular but he got all offensive)

No worries , I won't be coming back for while.

Your post should be sounding about exactly like mine by then.

[willrieffer]

Do you agree that Lavellenie does a better job of not fighting the poles elemental rotation better than Bubka?

I don't know that I can say as I don't exactly know what we would be talking about here. I have no idea how you see Bubka "fighting" the poles elemental rotation. I have read your ideas in the thread, but again, am not sure quite what to make of them. I will offer my thoughts as best I can.

The two swing differently to me, very differently, and at opposite ends of the spectrum.

Remember there is a critique of Bubka saying that he could have used longer and softer poles. I contend this would have altered his swing timing. So he appears for all intents and purposes as say a good HS vaulter working on a shorter pole than maximum. And in effect has to speed up his swing to cover for the speeded rotation of the pole. As above the vault occurs in less than maximal and ideal time. That is a longer softer pole vault would take more time from take off to clearance and so the swing rate and time would be longer. So even on the "shorter" poles Bubka could slowly push the WR this way and earn his incremental rewards from the USSR. He could, more or less get away with what I call "swing progression" which is being forward of the ideal swing angle in time. This is how I came up with all of this. Watching novice vaulters get too far forward and time where the pole doesn't compress enough, starts decompression early, and kills the vault. There is, then, a tolerable window for the CoM in its path for the vault to occur. It maximizes near the vertical of the gravity vector. This is why "under" can be less of a problem if the CoM can be kept back. This is what Dossevi shows us. It's worse to be tilted back, taking off "swing progressed", than it is to be purely under but being able to retain the CoM swing rate relation to the vertical. This is a key point. It doesn't say this is ideal or maximal about take off mechanics, which is what some have, I guess, tried to read into what I've said. It just makes of what the gravity relation and swing angle does to pole compression and how that is a benefit.

Lavillenie is the other end of the spectrum. His comparative disadvantages require him to squeeze from his mechanics every last bit of efficiency.

As somewhat counter to your idea of "fighting" the rotation, I find Bubka's vaults, his style, very aesthetically pleasing to watch. He makes it look easy! And in fact I propose an argument above that says between his speed and take off mechanics it was easy. Too easy. He doesn't have to fight pole rotation, he doesn't have to work to drive it to maximal, he simply has to get over the pole in time and that's easy as well. He has vestige energy from his run that he can allow into his swing rotation and energy under pole braking. It shows up as his high swing rate in say the IAAF data. And this is where an why in analysis he comes out as less efficient than Lavillenie.

Will

[grandevaulter]

https://www.facebook.com/video.php?v=10 ... =3&theater

Rumor has it that Renaud heard about this study from the kinetic physicist, Willriefer on this forum and how accurately he described his technique. Translated from Francois to English:" You clever Americans are on to something here. Watch me perform the energy conservation body into a gravity vector by keeping my com low for an extended period of time and make up for my delay with a tuck" "I really conserved energy on this one by using the viscosity of the h20 in a transformed molecular structure" "Hopefully these geniuses know a chemist too"

[KirkB]

... You clever Americans are on to something here. Watch me perform the energy conservation body into a gravity vector by keeping my com low for an extended period of time and make up for my delay with a tuck ...

Grandevaulter is being sarcastic of course, but like most comedy, the humor is in stretching or twisting the truth a bit ... not much, just a bit.

I don't think it's any big secret that tuck-shooters try to keep their CoM low by pressing with their bottom arm to put more potential energy into the pole (by more bend); and then tuck to keep from stalling out.

But if that's all that this gravity vector thingy is, then RL's technique is nothing more than a tuck-shoot. What else is distinct about his technique? Does RL just tuck faster than others? How?

Without clouding his technique with fancy phrases like "gravity vector" (which really just means "The force of gravity per unit mass at a given point"), what is DIFFERENT about RL's technique, in comparison to a tuck-shooter? I think he has a better run, plant, and takeoff than most tuck-shooters, but what is it after that that sets his technique apart?

What I'm really struggling with is how he can invert so quickly, without the aid of a "good" swing (like SB's), and in comparison to other 6.00m tuck-shooters?

Is it possible to answer this in a single sentence or paragraph, without any jargon?

Kirk