GRV: Lavillenie - From Stall Swing to World Record

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby grandevaulter » Tue Oct 27, 2015 10:12 pm

https://www.facebook.com/94190594793/vi ... =2&theater

KirkB wrote:Petrov may have overlooked the benefits of a lower COM (by dropping the lead knee).


He doesn't drop it much in this practice video. Is it intentional?

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby KirkB » Tue Oct 27, 2015 11:57 pm

This vid is hot off the press (just today, I think), posted by none other than RL! Good catch, GV!

Given the newness of the vid, I'm impressed that it already has 2,941 likes, 47,298 views, and 37 comments (none more than 10 hrs ago) from his friends and followers! :yes:

In case anyone missed it, his comments under the vid were:
Renaud Lavillenie wrote: The legs are heavy, the body is tired, but it is good anyway! The first sessions are on momentum reduced in order to make a good amount of jumps with the quality of course!

I think "momentum reduced" is google's loose translation meaning "short run".

You will also notice a question (and an observation) from our buddy DB (6 hrs ago):
David Bussabarger wrote: Are you working on changing your lead leg action at take off? You are driving it up more than usual on this vault.

My comments ...

DB: My eyes see RL HOLD it up more, rather than DRIVING it up more. On his competition vaults, correct me if I'm wrong, but I think he still has good lead knee drive, but then drops it. The antithesis of driving the lead knee would be Jason Colwick's double-leg swing technique. Agree?

GV: I think this may be one of RL's first training sessions over a bar - in preparation for 2016 indoors and outdoors (Rio). So we cannot draw too many conclusions from a VERY early-season short-run vault. Looks like a 7-stepper, but it may be 8 or 9 (no more). I wish the vid started a few secs earlier. For these reasons, he may be: (1) now intentionally trying to keep his knee up (as a new technique that he's trying); (2) doing this ~8 step drill the same way he did it last season; (3) just playing around.

I don't think it's option #3, because he says "with the quality, of course".

My guess is option #2, pending however he answers DB's question (which is also GV's question). I wouldn't get too hung up on thinking that he's majorly changing his technique so early in the "2016" season.

When RL did 6.08 indoors last January, we talked about his technique here: viewtopic.php?f=31&t=43971, and I commented that his backyard vaulting technique had almost no pause (a la Petrov Model), and that (over the years) he's had less and less pause. I can't find the backyard vid link - it would be helpful if anyone can dig that one up.

Just sayin' that you can't read too much into it from a vid of a one-off short run vault.

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby willrieffer » Thu Oct 29, 2015 12:23 pm

Hmmm.

Let me ask this.

If you were making a computer model of the pole vault could you not include the effect of gravity and the force of gravity on the pole? Because this is what you guys continually put forth here. That it isn't really important...

And the compression force is going to vary as the angle from the CoM to the top hand.

There has been a continual political pressure that I, in using physics to analyze the vault, should stick to pole vault terms. This is a part of the problem. IF you are using physics to analyze the vault, then you need to use physics and its terms. When I try to talk about the gravity vector in a field, you guys get lost and confused even when I clearly post several outside sources explaining it.

TO clarify again. I have never criticized the Petrov COACHING method or anyone that uses it. SO when I talk about say grandvaulters "ignorance" I'm not at all talking about his coaching ability. Heck, lets give him a PhD in pole vault coaching. That does not make him any sort of authority on physics and is no shield from that ignorance.

Let me use an example that is not so close to home. In one of Bryan Clymer's vault videos he states about "rowing", 'Rowing destroys energy, and Petrov knows this'. Well look, here we are talking about a Netownian Physics analysis which leads to a problem. In Newtonian physics energy cannot be "destroyed" and so Clymer's analysis of what is taking place is wrong. Energy in this case can only be dissipated or misdirected, and in this case as is in general the case its being misdirected. It's at this point I would feel that at least some of you would take a shot at saying, "Ooooh, that Will, what an idiot, he's pro rowing!". But sadly, no, this is not the case. What is the case is that the physics analysis can't be right and that rowing cannot "destroy" energy. This doesn't mean rowing is good but that the statement about why it is bad is not, and cannot be, correct. Rowing therefore has to have another physics based reason for being a bad method. And knowing this might help one understand the vault better.

And, I mean, I can answer why rowing is bad. It's pushing the CoM forward and up in time ahead of schedule. It's misdirecting the CoM even as its an energy positive effort by the vaulter i.e. they are doing muscular work.

These sorts of things crop up all the time and it was the point from the get go.

IF Lavillenie is dropping the front leg, extending the back leg back, and keeping the lead arm almost fully extended in the post take off, these are all things which necessarily must lower and keep his CoM back. Its geometric. The comparison is to where his CoM would be with a Petrovian bent arm, a normal lead leg, and less extended back leg, which is the more common form of the vault. It's geometrical and logical. You want to make some comparison with another vaulter. That's not exactly going to work. I mean I said you could compare the CoM paths....

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby willrieffer » Thu Oct 29, 2015 1:20 pm

grandevaulter wrote:
willrieffer wrote:The problem is that you think there needs to be a "scientific" response to your practical observations. That's not how "science" works, or, you're working backwards. In this, the property of pendulums is proven science which YOUR observation goes against. OR, again, the point of proof is yours.

Indeed I say they CAN swing at the same speed, but only if they are actively regulating the swing speed.


Let's work backwards, you seem to think that's what works best for me. (first take a look at another one of your statements)
willrieffer wrote:In another thread grandvaulter posited that two vaulters of different heights would free swing at the same velocity. This is against well established principles of physics. They may indeed swing at the same speed (and where he used his eye to tell me they did), but not "freely". The natural movement of the shorter vaulter would be to progress faster through the angle...


Let's go through this "backwards" with a practical thinking coach. Perhaps a story problem:

A stickman comes to pole vault practice. He is an ordinary stickman, that acts like a pendulum. Well I guess he's not that ordinary, he's a one arm stickman pole vaulter. He comes to his coach, the coaches name is coach Strawman. Stickman asks coach Strawman what he should do today. Coach Strawman tells him to get back on the runway and jump from 8 lefts. He tells Stickman to swing his body perfectly straight. "Don't break at the hips, just swing like a pendulum, like the pendulum I saw on Willriefer's youtubes and cut and pastes".

Stickman runs up (very fast), plants and then swings his feet to inversion, 180 degrees from the earths plane on his one arm/hand axis. He totally resembles a pendulum. He asks coach Strawman; "Did my hips swing faster than my feet?" Coach Strawman says; "Idunno, I'm just a practical strawman coach" . Coach Strawman asks; "Did your hips reach 180 degrees before your feet, I can't tell, I just use visual observations, but WillRiefer thinks your hips traveled at a faster velocity because they are closer to the axis just like a short vaulter and your feet traveled at a slower velocity because they are farther away from the axis, similar to a tall vaulter, he claims the latter to be science".


Uh, talk about a Strawman...

What is the effect if Stickman happens to be a beginning vaulter and decides to pull with his arms shortening them and raise his legs shortening them?

What then does this do to the compressive force of gravity on the pole in the post take off?

Yeah, again, you have little to no idea what you are saying here in particular in being pertinent to my point. In short...

WillRiefer thinks your hips traveled at a faster velocity because they are closer to the axis just like a short vaulter and your feet traveled at a slower velocity because they are farther away from the axis, similar to a tall vaulter, he claims the latter to be science


It's indicative that you have to put words in my mouth to prove your point. The tangential rotational velocities of these body parts are different, however, the CoM's angular velocity here, and its effect on pole compression would be what matters where this argument is concerned.

You have simply attempted to show what has been a known property of fixed length pendulums for some centuries. That the tangential velocity varies with the distance to the pivot (I mean I guess that is what you are trying to illustrate as if that is the case, you got it backwards). The further from the pivot, the greater the tangential speed. So, I mean, credit for getting one of the basics of pendulums, but, you know, it makes no argumentative point against my position. None. Zip. Zero. Nada...

My point (and long have a labored at it...) is the effects a vaulter can make by means of using his body to manipulate and move the position of the CoM, lengthen the distance, as well as the use of the hands to manipulate the speed of the CoM in time through the vault. Or, you know, you still don't get it. But, hey, keep swinging slugger..

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby grandevaulter » Thu Oct 29, 2015 10:56 pm

willrieffer wrote:willrieffer wrote:In another thread grandvaulter posited that two vaulters of different heights would free swing at the same velocity. This is against well established principles of physics. They may indeed swing at the same speed (and where he used his eye to tell me they did), but not "freely". The natural movement of the shorter vaulter would be to progress faster through the angle...

willrieffer wrote:SO when I talk about say grandvaulters "ignorance"

That is your opinion. But not so fast.

willrieffer wrote:Yeah, again, you have little to no idea what you are saying here in particular in being pertinent to my point. In short...

Yes, I have provided more than sufficient points that the variables that you fail to take into account render your arguments useless to most anyone except yourself.
You say that a shorter vaulter swings faster than a taller vaulter, you fail to take into account variables such as arm reaches that can make a 5' 6" Stickman into a a 6' tall Stickman (like your cut and paste NASA pendulums, but space orbits don't have variable arm, torso or leg length).
PVstudent wrote:The instantaneous and the average angular velocity about the hand axis of Stickman's feet and hips will be the same in angular displacement magnitude!

I put it in practical terms and PVstudent explained it with a scientific solution. Did his feet arrive at 180 before his hips? How does the instantaneous and the average angular velocity apply to RL's 6m vaults compared to a TALLER (disclaimer: not taking into account on the variable of arm length) vaulter. (Disclaimer: not taking into account the composition of the other variable breaking points at hip joints and torso).

PVstudent wrote:The fundamental premise amongst the many that have been made by WIll is not supported by the relatively recent evidence in Lavillenie's real world vaulting performances. The video below shows that he does not keep his COM (Vaulter's Centre of Mass) down and back in the pole support phases of the vault.

The pole support phases are defined as occurring between the instant ground take-off foot contact is broken until the instant the final hand grip in contact with the recoiling pole is released completely and the vaulter is airborne (free for indirect contact via the pole with the earth and subject only to air resistance and gravitational force causing a constant -9.81m/s/s acceleration on the vaulter vertically downwards).

https://youtu.be/sMpzTO8h5qk


willrieffer wrote:My point (and long have a labored at it...) is the effects a vaulter can make by means of using his body to manipulate and move the position of the CoM, lengthen the distance, as well as the use of the hands to manipulate the speed of the CoM in time through the vault.

Fortunately a vaulter is not just a Stickman or Stickboy and has some cognitive abilities, similar to the latest RL practice video. Does it appear that he is manipulating his vault with his hands in that one?

willrieffer wrote:But, hey, keep swinging slugger.

I'll keep swinging tall and for the fence.

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby Tim McMichael » Fri Oct 30, 2015 11:25 am

I can't stay out of this debate. It has always been my understanding that the longer and further from the chord of the pole a vaulter can keep their COM, the higher they will go. The reason all very small vaulters have done this is because we have to. It's the only way we can compete. You can see this at work in Joe Dial, Jeff Buckingham, and to a lesser degree, my own vault. What you have in Lavellenie is someone who can do this with a free takeoff. I always believed that this could produce a world record and it was awesome to see it happen. I don't really understand what the issue is here. As far as I can tell it's fundamental physics that everyone from the stiff pole era knew. If you hang a weight on a one foot long rope from the top of a pole, it will take more energy to raise the pole to vertical than if you hang the same weight from a four foot rope.

It's here that we find that if we look at WC shorter vaulters like Lavillenie, Dial, Greg Duplantis, Jeff Buckingham, etc, you find they are all lead arm lockers. Why? Because they have to do so to stop swing progression where swing progression is where the COM rotates forward lowering pole compression and causing the vault to fail or be infringed. This has almost NOTHING to do with force or pressure on the pole at the lead hand. Yes, it will feel like pressure and there MUST be an active/reactive force, but the important part of what it does is press or hold the COM back...which is part of the PB method! It was imperative to keep the COM/hips back!


Whether or not this is correct, this is certainly what we were working on when Joe at 5'8" cleared 19'6" with a 15'9" grip. His father worked this out from first principles with no formal training, background or education at all. I have often said and will repeat here that the long bottom arm does nothing to bend the pole but does a lot to keep the vaulter's COM back. The language I use there is deliberate, "long" not "stiff" and certainly not "locked."

https://www.youtube.com/watch?v=wAiOmgK_Fiw

Points to note here are that his COM does not pass the chord until 007 when the pole is nearly straight and he doesn't finish coming out of his tuck until 008 when he is in the middle of his turn. He also never gets close to "inverted." Yet this still a 53" push off.

One of the reasons I think this debate is so difficult to resolve is that many if not most of the things a vaulter has to work on to jump like this are the opposite of what is emphasized in the Petrov method that has held sway for so long now. What I see in Lavillenie is a melding of the two. Free takeoff and low COM followed by a tuck.

I'm more than willing to entertain the idea that I could be wrong here, I certainly was about the role of the bottom arm a few years ago. Help me understand how.

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby KirkB » Sat Oct 31, 2015 12:09 am

Good points Tim (as always).
Tim McMichael wrote: ... the longer and further from the chord of the pole a vaulter can keep their COM, the higher they will go.
At the expense of slowing down the swing, thus "pausing" while waiting for the pole to rotate (thus limiting how they will go).

1. You noted that JD didn't have the free takeoff that RL has (JD's pole bends before liftoff)

... but two other points to consider:

2. The "pause" (or "flatback") timing of JD v. RL

3. The role of Agapit's "Theory of Continuous Motion" in JD's v. RL's technique.

My opinion:

1. JD's pre-takeoff bend is a braking action (inefficient; loss of energy).

2. JD pauses longer than RL i.e. You can count more vid frames in "flatback" state on JD's vid v. RL's.

3. I agree that bottom arm pressure will keep the COM lower, but at the expense of slowing down the swing; not rolling the pole quickly enough; and not inverting soon enough (thus the need for the dreaded "pause").

RL seems to have found the happy intersection of the Petrov Model (free takeoff; no pause) and the Drive Vault Model (low COM) - taking the best of both.

Your opinion?

Kirk
Last edited by KirkB on Sat Oct 31, 2015 12:26 am, edited 1 time in total.
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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby KirkB » Sat Oct 31, 2015 12:21 am

willrieffer wrote: ... Lavillenie, Dial, Greg Duplantis, Jeff Buckingham, etc ... are all lead arm lockers.

Tim debates this. Personally, I don't care whether it's a lock or pressure or any other kind of resistance. A duck is a duck. It slows down the rotation of the body around the top arm (one pendulum); and it slows down the rotation of the pole around the box (the other pendulum).

willrieffer wrote: ... Why? Because they have to do so to stop swing progression where swing progression is where the COM rotates forward lowering pole compression and causing the vault to fail or be infringed. This has almost NOTHING to do with force or pressure on the pole at the lead hand. Yes, it will feel like pressure and there MUST be an active/reactive force, but the important part of what it does is press or hold the COM back...which is part of the PB method! It was imperative to keep the COM/hips back!

As mentioned above, this is at the expense of having to "pause" while waiting for the pole to rotate.

I partly agree. YES, they do it to hold the COM back and low, but NO, the unfortunate negative side-effect is the "pause".

I see a lot less pause in RL's technique than Joe Dial's and other "drive vaulters". Or is that what you're saying too?

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby Tim McMichael » Sun Nov 01, 2015 12:57 am

It's too late for me to think well, but let me just say this for now. A fast swing adds energy to the vault. That's indisputable. Keeping the COM low and back also adds energy to the vault. The focus of Petrov's method is on a fast swing. The focus of a drive vault is on the low COM. Both methods have a long and glorious history with multiple records and championships. At this point I am more interested in learning all I can about how and why each method works and much less interested in trying to decide which is best. I personally think the drive vault is a little more powerful, but it is MUCH harder to learn and teach.

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby KirkB » Sun Nov 01, 2015 1:33 am

Tim McMichael wrote: Keeping the COM low and back also adds energy to the vault.

Tim, I'm having a hard time understanding how this is possible.

Let's take the simplest case, where the vaulter's body is locked (frozen) for a few moments without any motion in his arms or legs.

You are saying that this adds energy to the vault. How can this be possible?

The pole is still bending during these moments, so I can see how potential energy is transferred from the vaulter's body to the pole (due to inertia?), but I don't see how that's an increase in the energy of the total vaulter-pole system.

Am I missing something? :confused:

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby Tim McMichael » Sun Nov 01, 2015 3:46 am

I reasoned it out this way. I know that if you hang 45 pound plate from a foot long rope attached to the top of a 16' pole and then raise the pole to vertical with the end anchored in the box, it will take a lot of force to do this. If you take that same weight and hang it from a four foot rope, it will take much less force. If we look at the chord of the pole as simply a stiff pole that must be rotated to vertical, then the COM can be looked at as the weight hanging from the rope. The lower the COM in relation to the chord of the pole, the less energy is needed to rotate the pole to vertical. This means a higher grip and faster pole speed. I guess it would be more accurate to say that the low COM doesn't add energy like a fast swing does, it transfers the energy from the run more efficiently into the system.

I think this is why every great vaulter of the stiff pole era dropped their lead knee at takeoff. There have been plenty of fantastic vaulters in our time who do exactly the same thing. Hooker and Lobinger come to mind. Lavillenie is the first vaulter in the history of the sport to have a free takeoff and a low lead knee while also aggressively swinging the trail leg.

Let's take the simplest case, where the vaulter's body is locked (frozen) for a few moments without any motion in his arms or legs.


Locking the body in place isn't what keeps the COM low. Lowering the lead knee and keeping the hips as far behind the chord as possible while swinging is what does the trick. Your example is still relevant though. The vast majority of vaulters penetrate further when they don't swing than when they do. The tiny fraction of vaulters who penetrate more when they finish the vault either have a free takeoff and an aggressive swing. (Petrov) Or they have found a way to keep their COM low and behind the pole while they swing. (Drive and Tuck) Or they do both and set the world record. (Lavillenie) :D

Here is a really cool old video I stumbled upon.

https://www.youtube.com/watch?v=G_feuodm7e8

The part that's relevant to this discussion starts at 4:34.

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Re: GRV: Lavillenie - From Stall Swing to World Record

Unread postby KirkB » Sun Nov 01, 2015 10:09 pm

Tim McMichael wrote: I reasoned it out this way. I know that if you hang a 45 pound plate from a foot long rope attached to the top of a 16' pole and then raise the pole to vertical with the end anchored in the box, it will take a lot of force to do this. If you take that same weight and hang it from a four foot rope, it will take much less force. If we look at the chord of the pole as simply a stiff pole that must be rotated to vertical, then the COM can be looked at as the weight hanging from the rope. The lower the COM in relation to the chord of the pole, the less energy is needed to rotate the pole to vertical. This means a higher grip and faster pole speed.

Very true. :yes:

Tim McMichael wrote: I guess it would be more accurate to say that the low COM doesn't add energy like a fast swing does, it transfers the energy from the run more efficiently into the system.

That's what I was getting at. It doesn't ADD energy; it only CONSERVES energy.

But does it conserve more energy than a Petrov vaulter that has a higher takeoff angle; doesn't drop his lead knee; and meets the criteria for the Theory of Continuous Motion? :confused: There are two areas of potential delay in the Drive Model: (1) the "hang time" - instead of continuosly raising the COM; and (2) the pause in the flatback position whilst tucking/rocking back to a full inversion.

Tim McMichael wrote: I think this is why every great vaulter of the stiff pole era dropped their lead knee at takeoff.

Agreed. But it would also have been counter-productive to leave their lead knee up, because their poles didn't sink/bend to give them the time and space to invert with a shorter chord. Agree?

Tim McMichael wrote: There have been plenty of fantastic vaulters in our time who do exactly the same thing. Hooker and Lobinger come to mind. Lavillenie is the first vaulter in the history of the sport to have a free takeoff and a low lead knee while also aggressively swinging the trail leg.

Yes. The differences that I've noticed between Petrov Model and non-Petrov are (1) the speed of the swing; (2) the ability to invert sooner; and (3) the amount of pause while waiting for the pole to roll to vertical. And I think we should completely ignore those vaulters (like Okert Brits) that forced the bend to start prior to takeoff SIGNIFICANTLY, and INTENTIONALLY.

Tim McMichael wrote:
KirkB wrote: Let's take the simplest case, where the vaulter's body is locked (frozen) for a few moments without any motion in his arms or legs.

I didn't mean to imply that RL intentionally locked his bottom arm. You've already clarified that. I was merely trying to take a hypothetical situation (just as GV did with his stickmen) to make my point that once you leave the ground, staying low doesn't ADD energy to the vault; it merely PRESERVES energy. I've now made that point, and you've clarified what you meant about this.

Tim McMichael wrote: Locking the body in place isn't what keeps the COM low. Lowering the lead knee and keeping the hips as far behind the chord as possible while swinging is what does the trick. Your example is still relevant though. The vast majority of vaulters penetrate further when they don't swing than when they do. The tiny fraction of vaulters who penetrate more when they finish the vault either have a free takeoff and an aggressive swing. (Petrov) Or they have found a way to keep their COM low and behind the pole while they swing. (Drive and Tuck) Or they do both and set the world record. (Lavillenie) :D

And this gets us to the "gotcha" that I've always considered to be the flaw in a double-leg swing ...

Most Drive Model vaulters (yourself included) stay so low that they must tuck in order to let the pole catch up (in its rotation to vertical). I'm not against swinging low. In fact, I wish the vaulter could swing low (to gain the obvious advantage that you yourself discovered, and that's clearly shown in the Old School vid from Art of the Vault), but then somehow quickly invert without stalling out. That seemed to me to be impossible for a couple reasons: (1) the strength and coordination needed to do it; and (2) the inevitable stall that occurs after hanging low. I agree that RL has now done the impossible, so it's now back to being possible!

But isn't it ironic that the theory (that you've explained, and that's also explained on the vid) of why staying low is a GOOD THING (for Drive Model vaulters and Old School stiff pole vaulters alike) actually has THE FLAW OF THE PAUSE in it? :confused: I mean, you (a Drive vaulter) want to stay low (presumably because if you keep your lead knee up you won't penetrate as much); yet when you stay low, you've lost the time needed to invert without tucking, forcing a pause so the pole can catch up.

Or to say it another way, if you swung long (without tucking) as Bubka did, then you would stall out (the pole wouldn't roll all the way to vertical).

If you understand this quandry, please explain. My current position on this quandry is that I like the lower COM that a double-leg swing gives you, but not at the expense of pausing in the tuck. :confused:

Tim McMichael wrote: Here is a really cool old video I stumbled upon.

https://www.youtube.com/watch?v=G_feuodm7e8

The part that's relevant to this discussion starts at 4:34.

Thanks for the vid, and thanks to Coach Eric and Dave Butler (Art of the Vault) for publishing it. Very cool. :yes:

Starting at 4:34, the instructor states: "The highest grip that the vaulter can utilize is one that just permits the pole to reach the vertical. In any vault, the energy of the run and takeoff can be used to raise the body to a particular height. At maximum grip, that height should be reached when the pole approaches the vertical. The maximum grip of the vaulter will depend on the efficiency of his form, running speed, and his height. In this case, the line of dots represents the height to which the body weight can be swung. So far, the string has been hanging freely. This time we will shorten the string to see what happens. Now with the string shortened, and weight closer to the pole, we continue to raise the pole. With the amount of energy at his disposal, the forwards energy of the pole must stop when the weight has reached the height of the dots. The answer is clear that the vaulter must hang. In this way, he keeps his CoG low during the swing, and permits the pole to approach the vertical. The takeoff is the most important part of his vault. "

Sidebar: Notice that at 5:40, you can see that this steel pole actually bends slightly. This type of bend was even more pronounced with bamboo poles, and was a well-known phenomenon in the 1950s and 1960s. Bamboo poles preceded steel poles, and were actually more desirable due to this property. However, steel poles became more popular because they could be built more consistently, without fear of breakage, and to more stringent and more consistent flexes than having to find a series of bamboo poles with similar flexes.

Back to keeping the COM low by dropping the lead knee ...

Relevant to the Old School (stiff pole) Model shown in the vid, they had less choice than us fiber pole vaulters, because their poles didn't bend (nearly as much). So their COM traveled a much straighter line than ours (which is one good reason why they didn't vault as high as us). Whether the Petrov Model; Drive Model; RL Model; or Barber Model (yes, that's what Shawn's dad George has named his model), we could (and we did) control the path of our COM with greater precision than them. And (ignoring all the other reasons for now) some of us chose to keep the lead knee up (to swing faster; to add energy to the vaulter-pole system; and to invert quicker); and some of us chose an even lower (and more curved) path for our COM (to gain the advantage explained in the Old School vid; which was later re-discovered by yourself and others).

I've already asked this question 100 times (but still no good answer): Please help me to understand how RL can (1) have a free take-off; (2) get a good, low swing; and (3) invert quickly enough without much - if any - pause. :confused:

Kirk
Run. Plant. Jump. Stretch. Whip. Extend. Fly. Clear. There is no tuck! THERE IS NO DELAY!


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