Physics Based Critique of the Petrov Method

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Re: Physics Based Critique of the Petrov Method

Unread postby PVstudent » Sat Mar 29, 2014 4:21 am

Brilliantly expressed Tim and reinforces the Petrovian Method advantages that immediately follow the take-off foot leaving the ground in a “FreeTake-off.”

Please note that “Free” is referring to the notion of the vaulter experiencing minimal resistance from the pole that counters the vaulter’s motion (as represented by magnitude and direction of the vaulter’s total body centre of mass).

At no point anywhere in the vaulting process can the vaulter ever be truly “free” of the effect of the gravitational attractive force due to the distance apart of a vaulter and earth mass centres!
In running, jumping and projecting the body by means of a flexible pole, the vaulter is working against “gravity” (air resistance can be of assistance or a hindrance to vaulter motion depending on the environmental conditions) through direct and indirect contact with the surface of the earth. Upon the vaulter’s centre of mass reaching the peak height of its flight trajectory following pole release, the vaulter undergoes a vertically downward displacement accelerated by the negative downward direction vector and magnitude of the force of gravity.

I think understanding from a physics and biomechanical perspective the “how, what, where, when and why the composite material pole used in modern pole vault (post 1960 to date) is made to bend is the crux of problem and has yet to be understood by many coaches and many, if not most, relatively successful vaulters.

In your excellent, very clear exposition on the advantage to the vaulter of using a free take –off you do make an error in accepting that the planting box does not move upon the instant the pole tip makes contact with the rear wall!
I quote
Tim McMichael wrote:This goes to the fact that willreiffer is right about. From a purely physics standpoint, is is impossible for energy to go into the box. For that to happen the box would have to move.


The box does move!

Because the box is rigidly attached to the earth and the earth has an infinitesimally large mass relative to that of the vaulter the box is observed not to move whilst the vaulter possessing such a tiny relative mass experiences large effects, from the impact of the pole striking the earth, that are readily perceivable by both vaulter and external observer.

Newton’s action-reaction principle operates such that to every action there must be a simultaneous reaction of equal magnitude and opposed in direction. (If the box did not move Newtonian Law of Motion would not be operating! (It is accepted the collision in the impact is “elastic” not “plastic!”).

The inertial effect of the pole impacting the rear wall upon the vaulter, who is from that instant in contact with the earth via the pole, produces clearly observable changes to the motion of the vaulter’s centre of mass and has associated observable effects upon the vaulter’s body segment arrangement in relation to the hands gripping the pole. Some energy will be lost in the impact due to sound, friction and the “compliance” in the musculoskeletal system of the vaulter. On this I think there is agreement in viewpoints so far expressed.

Tim McMichael wrote:Any method that allows a vaulter to finish the vault and still land in the box is unsound. Not just because it us unsafe, though that is the main reason, but also because it will be a lower vault, even if it is successful.


Yes!!!!!!!!!!!!!!!!!!!! Yes!!!!!!!!!!!!!!!!!! I totally agree with you!!!

Tim McMichael wrote:That said, I do appreciate willreiffer's ideas and comments on this board. His was the majority point of view not too long ago and was advocated by no less that Dick Ganslen who was also coming from a physics background. It's good to rehash this debate, I think. If only because the arguments for an under takeoff can be surprisingly compelling.


Dick Ganslen, arguably the foremost Mechanics of the Pole Vault Guru of the late 50’s through to late 1970’s, did not, in my view, adequately consider the significance of the nature of the pole – planting box interaction dynamics in determining how, where, when and what occurs under differing combinations of pole-box impact phenomena.

Ganslen did introduce Euler beam bending theory considerations in pole performance but necessarily (given the era!) was limited to a purely statics analytical approach. Also, in my opinion, the publications gave disproportionate weight to the anecdotal evidence provided by the best vaulters of the day! In one sense this was admirable in that Ganslen did not censor the opinions being expressed even though he may possibly have had personal reservations as to the veracity of some of those opinions!

Forty years on the myths as to the efficiency and effectiveness of putting lots of stored elastic potential energy by pre-bending the pole before take-off are alive and well.

I hope that Willreifer and others will be persuaded that any advantage mechanically that may be obtained by this take-off technique of storing potential energy in the pole is “too costly” to the successful completion of the rest of the vault because of the high risk of catastrophic failure it presents for even the most successful vaulters on the planet let alone naive neophytes! (see video referenced below).

For those of us who have observed the evolution of Renaud Lavillenie’s technical development, let’s say from 2005 until his 6.16m World Indoor Pole Vault Record in 2014, it is clear that as his capacity to use longer grip lengths on longer and stiffer poles improved, his take-off point on the runway has moved from being “excessively” under in the horizontal direction toward that which minimizes pole resistance, namely a “Free Take-Off”. The laws of physics and mathematics dictate that this must be so given the constancies of the pole lengths and the vaulter anthropometry (stature, mass, body segment distribution of mass and segmental lengths, muscle mass cross sectional areas etc.,) on any specific vault attempt.

The formidable task necessitated by “ideal” take-off locations along the runway, even when very flexible poles are used relative to vaulter body mass, means that the vaulter has to achieve a greater amplitude of pole cord angle of rotation to be successful. This requirement in turn increases the vital necessity to safely rotate the total pole plus vaulter system towards the plane of the cross bar. The vaulter not only has to increase intentional focus on system rotation rather than pole bending but also must train to achieve greater proficiency and efficiency in optimizing the redirection of the transfer of momentum from the preceding run up and plant.

Given the relative ease and safety with which the Petrov-Bubka Approach can be and is being taught effectively to some beginners, it is interesting to speculate on what Renaud Lavillenie’s ultimate potential would / could be if he did not have to contend with the legacy of having learned to vault by taking off under and massively pre-bending the pole!

In the two jumps in this video below, one a Fantastic World Record and the next a World Record failed attempt could not better illustrate, to an unbiased viewer, the notion that simply using a massive pre-bend take-off is ineffectual, inefficient and inherently puts the vaulter at increased risk of injury.

It is my opinion a coach operating on this foundational misconception risks inculcating behavioural actions, beliefs and attitudes about pole vault technique that increases the intensity and probability of adverse pole vaulting outcomes for beginners and advanced pole vaulters alike that become extremely difficult to alter! This is despite the facts and wisdom known about the matter. C'est la vie!

http://youtu.be/ah6tgafM7ek
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Re: Physics Based Critique of the Petrov Method

Unread postby Tim McMichael » Sat Mar 29, 2014 2:24 pm

The box does move!


I concede the point and hang my head in abject humiliation. :crying: Yes...it does move. The only way I can think of to reduce this energy loss is to vault on a bigger planet. But then you have increased gravity, so......

In the two jumps in this video below, one a Fantastic World Record and the next a World Record failed attempt could not better illustrate, to an unbiased viewer, the notion that simply using a massive pre-bend take-off is ineffectual, inefficient and inherently puts the vaulter at increased risk of injury.

http://youtu.be/ah6tgafM7ek


I think Renaud's failure on that last attempt is an illustration of how safe the vault can be if you are trying to do it correctly, even when things go terribly wrong. Here you have someone arguably putting more energy into the vault than has ever been done in history. Then he misses the box. That's about as bad as it gets for a world class vaulter and I suppose it can happen to anybody, but watch what happens next. He cannot finish the vault, and even though things go about as badly as they can, he walks away with a minor injury. At no point in that crash was his life at risk. The average, under, hip flipping, high schooler attempting 15' with the standards at minimum depth is in more danger.

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Re: Physics Based Critique of the Petrov Method

Unread postby PVstudent » Sat Mar 29, 2014 9:29 pm

Tim no apologies necessary. The concept is very difficult to genuinely accept but is foundational to understanding Newtonian Laws of Motion.

Tim McMichael wrote:I think Renaud's failure on that last attempt is an illustration of how safe the vault can be if you are trying to do it correctly, even when things go terribly wrong. Here you have someone arguably putting more energy into the vault than has ever been done in history. Then he misses the box. That's about as bad as it gets for a world class vaulter and I suppose it can happen to anybody, but watch what happens next. He cannot finish the vault, and even though things go about as badly as they can, he walks away with a minor injury. At no point in that crash was his life at risk. The average, under, hip flipping, high schooler attempting 15' with the standards at minimum depth is in more danger.


I agree with your observation except to clarify three points:

1. Renaud has stated that the pole struck the rear wall of the planting box. He went on to say,the words used translate as, "... the pole jumped out of the box".

2. The cause of this happening according to Renaud's explanation was that he was 50cms under on the approach run ie., 50cms too close to the box when the pole impacted it.

3. Detailed frame by frame analysis shows that he had to make the classical adaptive body configuration changes to his take-off: tipping his torso laterally to left, shoulders tip (left shoulder lower than right), right hand grip arm elbow flexed and placed to the left so that the line of the pole is slightly diagonal to the primary plane of motion on box impact, total body inclined rearward with respect to the placement of the take-off foot which has been positioned right side lateral to the central line of his forward progression. Note that it was his bottom hand grip that was lost when the pole bend and incipient potential buckle to the left was suddenly stopped by contact with the pad! This also throws some light on to the role that bottom arm "pull" is contributing in the beginning of the first phase of vaulter pole support immediately on take-off.

I agree that in a lesser experienced and technically accomplished vaulter such an occurrence could be "very risky to say the least" and most certainly would fail to accomplish even the initial part of the first phase of pole support in the execution of the vault.

The video also reveals how pole tip slippage and bend contacting the pads "over-damps" and instantly decelerates pole and vaulter progression to result in the recoiling pole "shooting" the vaulter rearward.

To finish on a positive note examination of Renaud Lavillenie's 6.16m World Record Vault take-off (the dropping of the right leg after the take-off is another issue) fair minded observers would have to concede it shows more characteristics of the "free take-off" technique advocated in the Petrov-Bubka Model and that the failed 6.21m attempt revealed the technique
disadvantages that ensue from excessive pre-bend technique!

Application of sound principles of physics in pole vault will always trump erroneous ones!

The evidence must be evaluated on accurate, precise application of Newtonian Motion Laws before a "physics critique"will identify the flaws and fallacies purported to exist in the Petrov-Bubka Approach to pole vault and especially those principles specifically relating to take-off. What occurs immediately after take-off remains to be explored and discussed.

The "pull" controversy when placed under close scrutiny of the physics principles that must operate on the pole / vaulter total system immediately following the take -off foot breaking of runway contact I am optimistic can be shown to be a "straw man argument" and not problematical at all!
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Re: Physics Based Critique of the Petrov Method

Unread postby KirkB » Sun Mar 30, 2014 5:49 am

Good comments - especially by Tim and PVStudent.

Sometimes the box DOES MOVE enough that you can physically see it move! That's grossly inefficient, as that causes some of the impact of the pole to be absorbed into the ground (much more than if it's just the size of the vaulter impacting against the size of the earth). It's especially important indoors to ensure that the box is tightly bolted to the runway and anything else that's solid (since the entire runway could move - technically - under the impact of the vaulter striking the box. And the mass of the wooden runway isn't THAT much more than the mass of the vaulter). But I digress ...

What's far more important than all of this is the efficiencies within the vaulter's body. Being 'tight' on takeoff is SOOOOO-O important! If you're a rag doll on takeoff - aka a 'sack of potatoes', or if you don't have the strength to withstand the impact of the pole, or if you're not as tall as you possibly can be on takeoff, then energy is going to be lost - it's going to dissipate into your body in the form of friction and INEFFICIENT muscular movement - aka 'muscle burn'.

PVStudent can explain this far better than me in scientific terms. All I know is that from personal experience, I took less energy (wasn't quite as tired) on a good smooth takeoff and swing, compared to a bad or under takeoff where I was fighting the pole and gravity too much. In an earlier post, I referred to this as 'putting the brakes on'. Even bailing after a bad takeoff took more energy than sailing over the bar - even though my altitude was far lower on a bail.

I first noticed this when I started getting a smoother takeoff on my short run practice vaults. You won't notice the difference on any one vault, but after 20 or so - compared to 20 on a previous day where I was struggling with my takeoff - I noticed it. My conclusion from that experience was that the LESS energy I use up by an inefficient plant and takeoff - and swing - the MORE energy was left in my vaulter-pole system to shoot skywards. Again, I'm not using very scientific language here, but I knew that there were scientific reasons why my good vaults FELT better than my bad ones.

In a nutshell: Stretch tall on takeoff, and keep your muscles taught in preparation for the impact of the box and the swing - otherwise your energy will be lost bigtime.

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Re: Physics Based Critique of the Petrov Method

Unread postby DLM » Sun Mar 30, 2014 8:48 pm

kirk you are absolutely right in regard to the loss of energy if you are not stretched tall at takeoff, I am a coach of high schools vaulter both girls and boys and I still jump, in part because it is just fun, but also to show them that while I am older, slower, and probably with less vertical jump then they have, I can still out jump most of them using better technique . And it is because I have learned how not to loose energy, most of which comes when a jumper think that they have the strength to pull them self up off the ground at the moment of take off. The bent upper arm even if it is ever so slight acts as a shock absorber. Much in the same way that a seat belt does, it is designed to absorb some of the energy of your momentum and that is what happen as your arm is stretched back out. This is what I have seen and felt. I could be wrong.

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Re: Physics Based Critique of the Petrov Method

Unread postby willrieffer » Wed Apr 02, 2014 2:54 pm

I got capped net, friends, and with me an my kids I tend to run out somewhere in the back end of a month. Boo. It resets on the 2nd. Yay!

Well, some things answered, some things even more cloudy...

The Box Moving...

Well, certainly. And I've also proposed a counteracting moment. The foot that's also still on the earth (like the box) applying a counteracting force there, which is why the force measure is so high and why there is still potential for added increase. I mean we could talk about the elasticity of the system including the back of the box and down the runway and then to the vaulters foot, too, but is that necessary? We are also talking about magnitudes here, some of which are more or less dwarfed by other considerations....

It's going to be very very hard to really accurately measure the biomech potential of added force during the braking of a bend take off. Very hard. Lot of big brains, equipment, super slo mo measurements, and on.

I still haven't seen an explanation for the big vaults you can easily find of famous Petrov vaulters taking off with pole bend. Try looking at around 4:10 here.
https://www.youtube.com/watch?v=KUPBl4xToUM
I think someone said there was one. SO we have theory, and we have evidence, and we still don't seem to have a real answer. But maybe some clues. Someone talked about swing moment, and someone else about gravity, lets look there.

Bad Vaults. Most common its being under AND a bad posture take off. What happens? Well, lots of things, but you wind up with an immediately progressed swing, the vector now to compress the pole is off and gravity (that effect which is of most importance after take off) is draining more momentum from the swing itself while its being used less effectively on compression. The vaulter loses rotation in both the pole and swing, they get yanked up early and stall. This is box dangerous stuff. The best vaulters manage the effect of the gravity vector by body position in the swing. First in compression by trying to maximize its transmission into compression, and then in decompression by trajectory. I tend to think this is why the Petrov model works and is generally one of the safest methods. That the path it derives makes very good use of the gravity vector in the compression and swing phase. On a free take off at box contact they possibly get added swing momentum from gravity, and also get good effect on its transmission to the pole.

To me there are three crucial points relative to the gravity vector. 1 Take off and immediate post take off. Near perpendicular to max use and transmission of the gravity vector. It also possibly mines rotational moment if the hips are behind the hand at contact with the box. Then it minimizes its effect on swing as it has no negative force on the swing moment when the vaulter is perpendicular. 2 The possible parallel moment. At some point in a completely natural and fully extended swing the vaulter would come to a point where they would be completely parallel to the ground and the gravity vector. This would be, or is, a very bad position to be. Now gravity is in full effect in slowing the swing speed, and pulling energy out of the system and there is zero effect on the pole. So what should and what do vaulters do? They almost all shorten their CoM to the rotational axis to speed their rotation through this period. They do this with the legs and torso, shortening one or both. 3. Vertical. The vaulter now works toward losing as little energy to unnecessary rotation. Also, per the Petrov model, it can be used to regulate recoil speed, although the two effects align quite well. Again, an extended body rotates slower and thus through less degrees and so once the proper angles are achieved the vaulter wants to be extended as soon as possible.

Lavillenie. He drops the right into what I call a "quasi double leg", because it is just more efficient in the compression. It lengthens the rotational CoM and thus slows his swing and puts him in a better relation to gravity for longer. Then not to get "caught" behind, he has to radically alter his rotational length and pulls in both legs. That he does this so radically means that his rotation speed is high and he has to spend very little time in phase 2 where gravity can rob the rotational moment of energy. This, friends, is why he can vault so high without superior speed (and also gets more time and a better position to bail out of catastrophe!). He's radical in compression with the right leg drop. He's radical in transition with the amount of his manipulation of rotational speed and timing, and with this he gets into and out of his manipulation very fast and can get into extension as soon as possible. None of this is particularly Petrovian. Bubka was not a completely straight legged vaulter, and the relatively slow Tradenkov was even more radical in his swing manipulation around phase 2.

The Left Arm. You do not use the left arm to bend the pole. You use the left arm to work "back" and orient the torso. Or, more precisely, to stop unwanted swing progression. There have been a lot of guys vault with the bent left with worries about the swing moment and not slowing it. I contend they wind up with a progressed swing and actually lose both swing momentum and forward pole momentum.

P.S. Another anecdote. Two years ago I'm helping some kids. Over and over I'm working, "Plant High!", "Move back you're under!", "Drive deep!", etc. My 8th grade boy won conference, but only after he fought me all season to start his run 2 feet in front of where it needed to be! Also, I always keep the standards back from 24 to 30 and will not let my vaulters move them forward. So a coach called me "dangerous". I have no particular idea of why. Meanwhile they were letting a kid take off under, leaned back, arms bent, and where the vaulter was getting yanked straight up off the runway every time. They were also letting him vault with the standards as far forward as allowed as he took shots at 13' and was landing with his feet in the box on every vault....

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Re: Physics Based Critique of the Petrov Method

Unread postby dj » Wed Apr 02, 2014 10:43 pm

2. The cause of this happening according to Renaud's explanation was that he was 50cms under on the approach run ie., 50cms too close to the box when the pole impacted it.


This is miss information.... He was 50cm OUT at his mid

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Re: Physics Based Critique of the Petrov Method

Unread postby ADTF Academy » Thu Apr 03, 2014 9:14 am

dj wrote:
2. The cause of this happening according to Renaud's explanation was that he was 50cms under on the approach run ie., 50cms too close to the box when the pole impacted it.


This is miss information.... He was 50cm OUT at his mid

Dj



Agreed Miss Information... I have the slow motion video from the meet. He was out. Took off near 5 meters from talks with people there (and renaud at worlds).... The ultimate Pre Jump!!!!!!


Sad part is it lead to the pole bouncing out of box and planting into the mats.

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Re: Physics Based Critique of the Petrov Method

Unread postby ADTF Academy » Thu Apr 03, 2014 10:37 am

Can as a community we agree that each of you should take the time to Please Define the Words you are using in arguments before you begin your arguments. Great posts are made but your definition of key terms are not added to your long posts. No one knows what you mean when you say key words. They are in your head and different in others.

What is a Free Takeoff in your mindset?

Based on the answer to that questions the entire conversation changes massively. The issue with all coaches is we each have a thought process about a word, thought, theory, movement and action. That thought greatly causes issues when communicating with others who do not have the exact same thought process. This leads to people disagreeing even though they probably agree.


Watching all the videos posted by the original poster I would say due to the angle of the shots taken I would not call any of the jumps witnessed as being a bad UNDER TAKEOFF!!!!!


If your mindset of a free takeoff is that the athlete leaves the ground with no bend in the pole. Sorry IMO you have a skewed vision of the term Free Takeoff. That is approaching the notion of a PRE JUMP>>>>>>> They are not the same.


What saddens me is in three pages of posts no one said hey wait a second just cause there is slight flexion in the pole and the foot is on the ground why are you saying most of those jumps are in fact not free takeoffs? What is the definition of a Free Takeoff. Many have posted on it over the years yet it seems to get lost in our own imagination of that perfect moment in time. That perfect moment in time doesn't exist 100% of the time if ever. It is the issue with vaulters and coaches we try to be perfect or teach perfection in every movement their athlete does. It doesn't exists. We don't vault in bubbles. Sorry!!! You will only lead to your athlete going crazy and mental.


The free takeoff is a flow or continuation of movements not a position or moment in time. Its a series of events not a photo. It is the ability of the vaulter to move thru the full running and jumping action at takeoff while receiving minimal tension on their body posture by the pole as it begins the stressed sensation of the two fixed points (the box and the top hand). If the vaulter can finish their final stride without any major alterations to their posture than they have in fact completed near a free takeoff for that individual vaulter. The videos you posted IMO meet this general theme/criteria of a free takeoff to me and therefore the entire argument you are making is lost in translation. However, if the ideology of a Free Takeoff is that there is no bend in the pole at all as the toe breaks contact with the ground than you have a totally different thought process. IMO you think a free takeoff is a pre jump IE Markov. Sergey Bubka IMO achieved a free takeoff movement on most of his jumps over history.

A true under step that is not a free takeoff is an example here.
https://www.youtube.com/watch?v=L0P3H4iO1DU
If you're going to show a Bubka Under Step jump starting at 1:02. Show this one. I doubt this was his goal. Now this is an UNDER STEP and a Free Takeoff was not achieved on this jump!!!

An under step to most vaulters will result in a poor jump because they can't finish their final stride into a jumping sensation. IE a free takeoff. A bail is usually the sign of a poor takeoff and lack of a free takeoff achieved for said vaulter. Bubka was remarkable as the original poster made cause he could manipulate his body in the air to make up for a poor takeoff.

Or this one of Jean Galfione since he made the bar and I do believe I have heard he ran more of an under step on purpose... Please someone confirm or correct me on this statement. (not 100% sure on this) I would call this jump on the edge of no longer being a free takeoff. However, in his mind the sensation he feels is in fact a Free Takeoff. Is it a general term or based on the individual vaulter.
https://www.youtube.com/watch?v=H7MeU0DQ17Q


For me depending on the exact definition of Free Takeoff this entire post is just people posting for the sake of posting. I don't think everyone is on the same page with the initial post made. Until we know his definition of what is a free takeoff this is all pointless. I am guessing what he thinks should be occurring is exactly what the real definition of a free takeoff is and therefore he is arguing against himself. Bubka had and was attempting to perform a Free Takeoff IMO based on my thought process towards what a free takeoff movement consists of. I propose the Free Takeoff is based on the individual vaulter and their skill set. A free takeoff allows for a safe jump in the mind of the athlete. The danger comes when an athlete gets rocked and they know the takeoff was bad yet their #1 objective is to SWING. This is when we are in danger. The free takeoff (for said vaulter) sets up the swing. It's different for each vaulter.

Alan has proposed that there should be a PRE JUMP like Markov. Please keep the thoughts separate they are not the same.

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Re: Physics Based Critique of the Petrov Method

Unread postby willrieffer » Thu Apr 03, 2014 12:21 pm

ADTF Academy wrote:Can as a community we agree that each of you should take the time to Please Define the Words you are using in arguments before you begin your arguments. Great posts are made but your definition of key terms are not added to your long posts. No one knows what you mean when you say key words. They are in your head and different in others.

What is a Free Takeoff in your mindset?


Well, as I have done we have to go back to Bubka himself and his statements. He claims they in fact were shooting for a pre-take off by leaving the ground prior to bend initiation and were worried about losing energy into the box. He does talk about body position as well, but claims the idea of a pre take off crucial to the inacting their vault. In fact I think my post is aligned with yours very much. There is also an effort in the community to explain that pole bend take offs are detrimental, and yet the evidence for these things is spurious.

We can look at 3:10 of this vid.

https://www.youtube.com/watch?v=QGTdEhUW0nE

Which has radical pre take off bend beginning before right foot even hits the ground and if the vid is correct is a winning jump in a significant contest. Even I cannot advocate this method! Yet, if I were to believe some, this vault is not only improbable, but impossible in terms of physics. The vaulter here pretty much just runs the pole into position while maintaining decent posture. Then he doesn't even use the left leg particularly well. And he doesn't appear to end the vault without momentum over the bar and into the pit. Or, it looks highly radical and yet not particularly dangerous at least in this particular vault and outcome.

The concern for box energy loss is particularly odd. On one level, a deep purely physics level, we might have to say that indeed a vaulter is going to 'move the earth' when they vault, but the velocity is going to be very very low. And since for kinetic energy = mass times velocity squared, any situation where velocity is very low is going to be exacerbated by being multiplied by itself in velocities relationship to energy. It's a math situation nearing a limit of zero. And if the box bled any significant amount of energy from the system in time, we couldn't vault in the way we do. Instead of energy going into the pole, it would go out of the box. It more or less doesn't, and certainly not at a level or magnitude that we need be concerned about.

And so my most direct original point remains. SInce the Petrov model works, one can claim any sort of mechanism for its success without a lot of concern for the physics (or physics terms or even pole vault terms) involved. That they could have misguided concerns and also attribute success to technical aspects that in truth have little meaning. And for me it is much as you say. They got success because of the swing pattern they could evoke from the approach which has little to do with being off the runway prior to bend initiation in part because they could pull off big vaults from pre-take offs, well timed free take offs, and bend take offs.

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Re: Physics Based Critique of the Petrov Method

Unread postby PVstudent » Thu Apr 03, 2014 12:46 pm

To DJ and ADTF
Thank you for pointing out my mistake.

I mistakenly translated the transcript in regard to Renaud’s comments, which I had translated as “my marks were off about 50cms” as referring to his approach run check mark and take-off point instead of as 50cms “out” as both DJ and ADTF informs us.

The video evidence (internet sources only) of his take-off showed his take-off foot to be just under and hips well advanced forwards of that location before the pole could be considered to have struck the rear wall of the box. I could not determine from the video available to me where his approach run check mark was.

I would not in any way deliberately mislead and I concede most happily that Renaud’s run was out by 50cms.

However I do not, on the basis this video evidence (see below), agree that Renaud’s take-off was also “out” by that amount.
This evidence suggests to me that he was over striding into the take-off and was “on /slightly under” at touchdown for take-off.

From the two differing camera angles Renaud Lavillenie does not appear to be anything remotely like 50cms out. I think on this evidence the take-off is reasonably viewed as being “on” or slightly under. The cause of the pole bouncing out of the box remains to be explained, perhaps ADTF’s slow motion video will shed some further light on the matter.

ADTF’s slow motion video and the angle at which the shots were taken may indeed confirm that Renaud was out by 50cms. There is no indisputable evidence on the videos available in the public domain, that I have been able to find, to confirm the belief that the take-off in question could be “the Ultimate Pre-Jump.” The onus is on ADTF to verify that statement.

That Renaud in conversation revealed to ADTF that he “thought” he was out at take-off I have no grounds to dispute. The videos most readily available in the public domain cast some doubt on this claim by Renaud. I want to see the indisputable evidence before I change my opinion.

What video evidence there is available in the public domain of the jump in question is still a reasonable record of the actual event but clearly is open to further critical scrutiny.

Once again thank you to DJ and ADTF for pointing out my mistake.

http://youtu.be/3tM3gyC7fJA
Every new opinion at its starting, is precisely a minority of one!

ADTF Academy
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Re: Physics Based Critique of the Petrov Method

Unread postby ADTF Academy » Thu Apr 03, 2014 2:03 pm

PVstudent wrote:To DJ and ADTF
Thank you for pointing out my mistake.

What video evidence there is available in the public domain of the jump in question is still a reasonable record of the actual event but clearly is open to further critical scrutiny.

Once again thank you to DJ and ADTF for pointing out my mistake.

http://youtu.be/3tM3gyC7fJA


I hate to turn this into a different discussion away from the original one, but I wanted to address his incorrect statement.


I'll try to post pictures taken from the video at key moments. I won't post the video sadly. It may already be out there but its not my video so I don't post other people's stuff. Even the video you you posted you can barely make out the marks on the side of the track. He is way outside both the Mid Mark and Takeoff mark. As the WR occurred and as the fail happened I was getting texts from people at the meet in the front row. The comment he was 50cm out at mid and took off around 5 meters was made. Did he in fact get long at takeoff. I would say probably but remember he was 50 cms out at mid or 1 foot 8". A normal human would have ran thru being that far out. He took it up anyways he only knows one speed: ALL OUT. Pretty much an aggressive stud and a little bit crazy at the same time. The exact numbers would need to come from his camp of people catching Mid and TO spot.

If you watch the slow motion section correctly you will see at around 1:06 the pole is in the box than 1 second later its into the pits. He was not under. Sorry you saw it incorrectly, one of the photos I just took he is off the ground and pole still 100% straight. If I was a beating man he was out and when he finished his takeoff with upward pressure with his hands the pole tip kicked up and was on the top half of the box. Once the pole was stressed it popped out of the box into the pits. Just my rough guessing. I wasn't the one vaulting or in direct communication with him or his coach immediately after the meet till I saw him at Worlds.

He was out.

Mid Step.jpg
Mid Step
Mid Step.jpg (57.06 KiB) Viewed 6910 times

Take Off Step.jpg
Takeoff Step
Take Off Step.jpg (56.9 KiB) Viewed 6910 times

Take Off Location.jpg
Take off Location
Take Off Location.jpg (55.38 KiB) Viewed 6910 times
Last edited by ADTF Academy on Fri Apr 04, 2014 2:49 pm, edited 1 time in total.


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