Push off

[KirkB]

Pogo, I see you have posted a link to another paper: "POLE VAULT AS DOUBLE PENDULUM AND PENETRATION". I haven't read that yet, but I think my reply here is independent of that, so I'll go ahead and post this, and perhaps reply to your "double pendulum paper" post later ...

We can see now that Bubka's COM travel longer distance than anyone else and this is why he needs more speed. The correlation between speed and COM trajectory is significant: 0.75.

What came first ... the chicken or the egg? ... Cause and effect ...

I would say that:

1. Bubka runs faster than any other vaulter.

So ... beCAUSE he's running faster, the EFFECT is that he can ...

2. Grip higher
3. Move his body (i.e. his CoM) along a longer path
4. Raise his CoM to a higher maximum.
5. Clear a higher bar.

You can think of 3, 4, and 5 as really being one and the same - with the assumptions you have made (crossbar height = CoM peak) they have a 100% correlation. In the triangle that you drew, the hypotenuse (longest side) is the CoM path, and to the length of the vertical side is the max CoM and the crossbar height.

I think this is the same conclusion that Linthorne drew in his paper: http://people.brunel.ac.uk/~spstnpl/Publications/PoleVault(Linthorne).pdf

Unfortunately, short of recognizing that it exists, both Pogo and Linthorne have ignored the extra oomph of energy that the swing/extension add to the system. That's what I was hoping we could build into the formula somehow. [sigh]

Pogo, is this the other 0.25 of CoM trajectory that doesn't correlate to speed?

In Linthorne's paper, he just accounts for this by adding 1.00m to his theoretical predictions of attainable crossbar height - irrespective of individual vaulter efficiency. [sigh]

You will recall that we discussed the Linthorne paper in the "take-off point" thread, here: http://polevaultpower.com/forum/viewtopic.php?f=38&t=15636&start=12 However, we did not discuss this particular issue in any detail.

Kirk

[Pogo Stick]

Right. Pogo had a good idea, but it didn't pan out. His idea is that if you're actually doing a handstand on top of the pole, you're "reaching" a little higher if you're a little taller. But in reality, if your DOWNSWING and UPSWING are vigorous, and if you follow that thru with a vigorous EXTENSION, then you're already FLYING past that HANDSTAND position. The extra oomph that you might put on the pole by a flick of the wrist upon release is all that can be gained there - if that.

I am still thinking that taller vaulter has advantage. You cannot ignore the fact that taller vaulter have hips (or COM) closer to bar at the moment of releasing pole, no matter does he push at top or flying thru handstand. ...

But in the "taller handstand" position, he's had to exert MORE ENERGY to get to that point. He doesn't get that extra energy by luck or heredity. To get there, he must GENERATE additional energy (including takeoff speed as well as energy added after that) during his vault! And this extra energy is body-height agnostic. No?

How about this:
- taller vaulter can generate more energy trough longer swing radius
- taller vaulter don't need same amount of energy because his COM is traveling shorter distance (for same body weight)

[KirkB]

How about this:
- taller vaulter can generate more energy through longer swing radius)

Yes, he can ... theoretically ... assuming identical takeoff speed ... by better leverage ... if he's coordinated enough to do this! That's part of the illusive "efficiency" value that we're trying to identify and put into the formula, isn't it? ... NOT the "taller handstand" value!

But we're talking about the "taller handstand" value (~half his height) ...

- taller vaulter don't need same amount of energy because his COM is traveling shorter distance (for same body weight)

To clear the same crossbar, it's true that the taller vaulter doesn't travel as far. 100% of the reason that's true is due to his higher CoM on TAKEOFF ... 0% is due to his "reaching handstand".

In your statement "taller vaulter don't need same amount of energy because his COM is traveling shorter distance", do you realize that you switched your assumptions? Now, instead of assuming the peak CoM to be at the TOP of his "reaching handstand" (assuming the same grip for each vaulter), you're assuming that the shorter and the taller vaulters must both clear the same crossbar height! Or if you're suggesting that the taller vaulter would grip LOWER (to net out to the same crossbar height as the shorter vaulter), then that's not a fair comparison either!

You can't have it both ways! To compare vaulter to vaulter (apples to apples), do you want to compare vertical deltas (the distance from reaching takeoff to reaching handstand), or do you want to compare identical crossbar heights? Identical grip, or grip can vary? Identical energy, or less energy?

If it's "less energy, so grip can vary", then the taller vaulter will clear the same crossbar, so where's the advantage to him on the handstand?

Once you freeze your constants (i.e. assumptions) I think you will find (mathematically) that the taller vaulter has a definite advantage, but 100% of this advantage is due to his superior tallness ON TAKEOFF! ... not due to his "taller handstand".

I believe that this entire misunderstanding is 100% provable mathematically. None of it is a matter of opinion because of any different interpretatioins on what a vault consists of. (I don't think we have any!) Everything's "on the table", isn't it? Pure math?

Hey, I could be wrong ... I'm not an engineer! Convince me!

Kirk

[Pogo Stick]

Yes, he can ... theoretically ... assuming identical takeoff speed ... by better leverage ... if he's coordinated enough to do this! That's part of the illusive "efficiency" value that we're trying to identify and put into the formula, isn't it? ... NOT the "taller handstand" value!

Brits, Hartwig and Tarasov are all tall guys (194-196cm or 6' 5") and all went over 6m. So strength, speed and ability to create enough energy are not an issue for 6m club members. If we go little bit down in 590 range then we got 2m (6' 7") Viktor Chistiakov and 1.73 (5' 8") Joe Dial - that is 27cm (10.6") difference.
I understand your point and you are absolutely right, but I think we went too far. I am not trying to predict how high someone will jump if run 10m/s and grip 5m (as Linthorne did). My idea was to see is it possible to compare efficiency without using energy inputs/outputs, elliptic integrals, dyno platforms, moon phases, tarot cards, and other complicated things. I was looking for something like "rule of thumb", something anyone can check and use. At that journey the other people brings their own views and ideas and now I am not so convinced that push off itself is good measure for comparing efficiency of two vaulters. For example: average push off of 6m club is around 114cm, the lowest one is 110cm. If your push off is less than 100cm, all I can tell your is that your chances to jump 6m are very, very, very slim. Or, if you have push off 136 cm and you are not jumping 6m your name is Joe Dial. I am kidding Tim, Joe Dial is remarkable man.
What is more efficient? Clearing same bar with lower grip than shorter guy and "less effort" or clearing same bar using same grip as taller guy? Maybe we need to go back and define efficiency first?

In your statement "taller vaulter don't need same amount of energy because his COM is traveling shorter distance", do you realize that you switched your assumptions? Now, instead of assuming the peak CoM to be at the TOP of his "reaching handstand" (assuming the same grip for each vaulter), you're assuming that the shorter and the taller vaulters must both clear the same crossbar height! Or if you're suggesting that the taller vaulter would grip LOWER (to net out to the same crossbar height as the shorter vaulter), then that's not a fair comparison either!

My simplifications were:
- All jumps in the table are vaulters personal best results at that moment
- COM peak is at the same point (height) as crossbar. Actual COM is bellow the bar at the moment of clearing (pocket knife position). Please note that this fact is not related with vaulter height or bar height. If you are jumping your PB this is solid assumption - this is your best jump in the life. I can normalize all values to 6.00m or any other value if you want
- COM trajectory is straight line, not curve, but starting and ending point are identical
- COM is at 1/2 body height
- vaulter's height with hand up increase proportionally with vaulters height

Of course, taller guy CAN use lower grip and his COM will travel even shorter distance. At the end (handstand, inverted) his COM will be at the same height as of shorter guy with higher grip. If both clear same height, they have same relative push off. My "formula" will not penalize him because of that. This is his comparative advantage and we can discuss is that less efficient or not.
Second example: for the same grip taller guy will end up with COM higher than shorter guy when inverted. If they clear same height, shorter guy is better.
I want use numbers from real world, otherwise, we will end up comparing only vaulters with same take off speed, height and grip (both of them ).
To summarize, taller vaulter has more options than shorter one (all other relevant things equal or in adequate range):
- he should jump higher by using same grip (main reasons: higher pole angle at take off, shorter horizontal distance from standards and COG closer to bar when inverted)
- he should jump higher by using higher grip (same main reasons minus horizontal distance advantage, but he needs some additional energy input from either speed, swing, technique or all together)
- he should jump same height by using lower grip (again same main reasons, plus he don't need to "work" so hard)

I like Tim's explanation about relationship between grip and push off.
If you increase grip over the optimal value, your push off will decrease and vice versa. Having formula for that will be very useful. If you know that 5" higher grip will reduce your push off for 3" and you have slight back wind that day, then go for it - you should be still 2" in positive. But if you increase grip over the optimum, push off can go down for maybe 8" or you will not land on pit at all. It will be nice if we can collect some reliable numbers about this. With enough good numbers it is easy to find relationship.

I also like Barto's idea about ratio of grip height to time it takes the pole to travel to perpendicular. Time is little bit more complicated to measure, but definitely easier and more accurate than speed in last 5m. If camera angle is good, the error should be bellow 5%. Almost any camcorder is good enough for that. I would also like to see some numbers.

[KirkB]

My idea was to see is it possible to compare efficiency without using energy inputs/outputs, elliptic integrals, dyno platforms, moon phases, tarot cards, and other complicated things.

Pogo ... so what's wrong with moon phases and tarot cards? The moon affects the tides (lunar gravity), so I'm sure it must have some effect on vaulters mid-jump.

And your meet preparation would not be complete without consulting a card reader or palm reader. While you're at it, you should check your horoscope, to see if the day of the meet will be your lucky day!

Seriously, all your detailed explanations are well-reasoned, and I buy it all. Not that I fully agree with your "taller handstand" argument, but since you've already mentioned all of the other MORE IMPORTANT factors that can affect the outcome of a vault, I'm not going to press the point any further. We're in sync. My original complaint was merely that your assertion of a "taller handstand" being a distinct advantage was short-sighted, without mentioning all the other more important factors.

You've fixed that now.

I have a related idea regarding "common data points for PV video analysis" that I will flesh out soon, and post on a new thread. It doesn't belong on this thread, as this thread is (or at least started out as) all about "Push off".

Stay tuned.

Kirk

[Pogo Stick]

[ have a related idea regarding "common data points for PV video analysis" that I will flesh out soon, and post on a new thread. It doesn't belong on this thread, as this thread is (or at least started out as) all about "Push off".

Stay tuned.

Kirk

I also have one idea related with push off. You gonna love it. More about this tonight or tomorrow morning.

[KirkB]

I find today the following article on net: "POLE VAULT AS DOUBLE PENDULUM AND PENETRATION". ...

Pogo, this entire paper lacks substance. It's not really a paper in the scientific sense, from what I read.

What little data they provide is questionable. For example, they compare Seagren's 1968 Gold with Nordwig's 1972 Gold and Kozakiewicz's 1976 Gold, when in fact Seagren's PR was in 1972, and Koz's was in 1980. If they're going to compare Olympic gold medalists, they should at least compare their career bests! Seagren's was in 1968, Nordwig's in 1972, and Koz's in 1976. The data related to each of those jumps may be perfectly valid, but I have no reason to trust it.

Although there were a few tidbits of interest, almost all of their conclusions lacked meaningful data to back them up. They quoted many, many references, but I read very little original research. The paper didn't earn my respect.

And I really detested their use of the term "rock-back". However, that can possibly be explained away as a translation error, as the original paper was probably written in Greek. THERE IS NO ROCKBACK!

There were many, many other misconceptions and misinterpretations that basically make this paper not worth the paper it's written on, IMHO.

Kirk

[Pogo Stick]

[ have a related idea regarding "common data points for PV video analysis" that I will flesh out soon, and post on a new thread. It doesn't belong on this thread, as this thread is (or at least started out as) all about "Push off".

Stay tuned.

Kirk

I also have one idea related with push off. You gonna love it. More about this tonight or tomorrow morning.

Here you are:
In last phase of jump vaulter is totally inverted, in handstand position and in line with pole (which is parallel with standard). Pole recoil is pushing you up and, if your grip is not too high, you still have some horizontal speed that allows you to reach the bar which is at optimal distance for that given jump. Amount of push off depends of:
A) body proportions
B) speed when you release the pole

A depends on arm and trunk length and it is given by nature.
B depends on everything before that - take off speed, swing, grip, timing, pole flex, etc. Also, you can increase that speed by pushing from pole (if you have the chance) and improve your chances for clearance.

B shows how good your vault is regardless how tall you are. That speed determines flight phase. Bigger speed, higher flight.

I will try to estimate this flight phase or follow thru handstand as Kirk said.
Sit at the floor and raise hand up, trunk and hand straight and perpendicular to legs. Measure distance from hand to chest. My result is 75-80 cm.
Now, imagine himself staying in that position but turned upside down. This looks like the following picture:


Now add the pole and the bar:


If bar is at abdomen level and you have some horizontal speed you should be able to "clear" the bar only by manipulating your body parts and thus creating enough rotation around bar. By the way, center of rotation is exactly at your COM and its position is bellow the bar. I will never mention COM again today, I promise. If, in addition, you also have some vertical speed, your whole body will rise up and you should be able to clear higher bar.
The difference between those two clearances is your efficiency. Are you with me so far?

As usual, I will made some additional assumptions to simplify everything and make calculations possible but keeping results as close to reality as possible. This is known as engineering approach. If results are far from reality, this is known as marketing:
- ignore the fact that bar is 30-50 cm far from pole. I will try to add this in calculation later
- ignore the fact that flight trajectory is curve (same as cannonball) and substitute with straight line. This is pretty good approximation for such short flight. I will also try to add this later
- assume that humans proportions are "linear" and for example 10 cm taller person has 10 cm bigger distance from hand to chest
- assume that pole and body are perpendicular to ground looking from runaway
- the accuracy of input numbers is unknown (except maybe for Bubka). This increase volatility and accuracy of output results
- even if all numbers are 100% correct, because of low number of samples (only 12 vaulters) the results needs to be considered "Cum Grano Salis" (with caution)

I will use myself as reference. Let say that "magic number" is 77cm. I will deduct this value from each vaulter push off. Please note that it doesn't matter if distance is 10, 50, 70 or 100, the proportions will be conserves. I am probably wrong about this number, if someone has more accurate data, I will change it. The final result will show the distance they really flight:



Bubka and TIm Mack are the best. Galfione probably can thanks to "hand of god" for being so high on the list. The "worst" are Tarasov and Brits.
If I do the same calculation for Joe Dial, his flying distance is amazing 63 cm or 2 ft - almost twice higher than Bubka. What a man!
Few facts:
- taller guys (190 cm and over) generally are not so impressive as shorter (less than 190 cm)
- average grip for both groups is almost identical - 508.8 vs. 508.7
- shorter guys have 2 cm better average push off (115 vs. 113)
- shorter guys can flight in average 10 cm higher
- average vaulter's height between groups is 192 vs. 185

So, in average, 7cm shorter guy jump 2 cm higher with same grip and his body can flight 10 cm higher.
And finally: in average, tall guys can compensate almost everything by using advantage of his body height - QED!

Don't take these numbers as a holly grail. My assumptions and simplifications reduce accuracy of results although for same percentage for each vaulters. This is not science work, it is just for discussion purpose.

[dj]

good morning...

well I was at the airport all night last night.. weather.. sand storm..

I have two decathletes competing today..

you mentioned camera angles.. i assume it is to have comparable data...

what i have done is find a "reference" point that is reasonably accurate from any angle.

i time the complete vault with these reference points...

first the takeoff is when the pole is up.. the foot on the track and the knees even with each other…thighs parallel…….. that way every vaulter will have the same… reference point…

second is the maximum bend……. And the back “flat to the runway”… I think these two points in the swing should be the same (occur at the same time) in every vault, but I have found differences based on the “bend” qualities of the pole…

the last time I take id the maximum height of the COM off the top of the pole..

this way the angle of the filming doesn’t have a major impact on the data…

I do most of my comparisons with Windows Movie Maker…

dj

[dougb]

Efficiency

For those of you who have access to the data, how about the ratio of body weight to pole stiffness given the same grip.

???????

Doug Balcomb
PV Coach, Colfax HS

[Tim McMichael]

My thoughts on the fly away are fairly unorthodox, as you would expect, and are based around my understanding of the model that we developed in Oklahoma. So as to not be redundant, here is the link to the rough sketch I gave of this technique some time ago.

http://s43076.gridserver.com/forum/view ... 378#p83299

I am going to run into the same problem I had with my “Manifesto.” Most of what I have to say is diametrically opposed to conventional wisdom, but is grounded in personal experience. As has been previously noted, Joe Dial’s air time was double that of the best of the six meter club, and while he did not jump that high, I think his PR of 5.95 is close enough to make this discussion relevant.

I am going to tentatively submit that his astonishing superiority in this phase of the vault was not because his athleticism was superior to these other great athletes, but because his method was significantly different. I also need to preface these remarks with a few caveats. I am not in any way suggesting that this technique is superior to any other, nor am I suggesting that anyone run out and try to do this. It rest of the foundation of a method that is prohibitive in its difficulty. It also favors the smaller, lighter vaulter with a superior strength to body weight ratio. The primary thing I want to communicate is that this method is based on elements of physics and physiology that are not generally taken into account when discussing this phase of the vault.

Joe’s father, Dean, invented this technique specifically because his son was the smallest vaulter in the world over 5.50 at the time, and he reasoned that something had to be different from the method used by taller athletes with equal or superior athleticism. Otherwise Joe would not be able to compete. His solution was based on an innovation that is utterly counterintuitive when applied to the vault. A lower center of mass through the second half of the vault increases the speed of the return of the pole, as well as putting the vaulter in a position to exert maximum force in the extension, turn and push. This force is enough to increase the fly away by as much as eight inches above what would be the result of a passive position on the pole.

It has been argued that the tucked position is passive, and that no force can be exerted by the athlete at the top of the jump. Both of these observations are true when applied to conventional technique. In a bad jump using the Petrov model the tuck is used as a passive move to try to catch up with the pole after a horrible takeoff. In a good jump, however, the vaulter is able to swing his hips to his hands with very little bend at the knees and then extend to vertical immediately afterward, while the pole is still bent. The earlier this happens the better, but from this position it is impossible to add energy to the top of the vault through any muscular effort on the part of the athlete. They are fully extended, so there is nothing else they can possibly do. The position of the body is static, and what the vaulter must do is stay as close to the pole as possible. Anything else will cause them to flag out as the weight of thier legs pulls their center of mass away from the pole.

I have already argued that the tuck, if done properly from a driving takeoff and swing does not rob the vault of energy. I am just not sure how anyone can argue against the law of conservation of angular momentum. It is an inviolable principle of basic physics. As the swinging body shortens its radius the rotation accelerates without loss of energy. While the power of the swing is not lost, the vaulter does end up in a very different position from the athlete using the Petrov model. The drive vaulter ends up in the position Mr. Dial referred to as “the bucket.” The knees are very close to the vaulter’s chest, and the hips are below their shoulders. Proponents of Petrov believe that from this position nothing good can happen. This is because, from their experience, an athlete who ends up in this position is in the middle of an already ruined vault. And they are right. At this point, this athlete has lost all energy and is hanging on the pole like a dead weight. The fact that Joe Dial could come from this same position and push off 52” over his grip while clearing 5.95 means that strict proponents of the Petrov model may be missing something.

A drive vaulter, from this same position, has all the energy they exploited and developed in their takeoff and swing, and is still adding energy to the jump. Far from being a passive position they are still pulling as hard as possible as the pole rockets toward the bar. The hips stay low throughout the return of the pole, thus placing the vaulter’s center of mass closer to the axis of rotation. This is not because they are passively waiting for the pole to finish, as it appears, but because the return of the pole is so powerful that no amount of effort on the athlete's part will allow them to catch up with it till it stops moving. This is because the position at the end of the swing allows the pole to return much faster than it would if their hips were at their hands, which would place most of the weight at the very top of the pole. The tucked position actually makes the pole stiffer after the vaulter has already penetrated. They are also in a position to turn through the shoulders. The Petrov vaulter’s shoulders are perpendicular to the pole which only allows them to rotate as though in a barrel that is right side up. The direction of this turn can add nothing to the top of the vault. This is why there are so many of Bubka’s clearances that are sideways, or with the bottom hand extended and the top hand drawn back. His bottom hand is the only part of his body in position to guide his rotation, and is thus the dominant arm at the top of the vault. Sometimes his vertical velocity is so powerful that his left arm's input is not enough to complete his turn before he leaves the pole.

The drive vaulter’s shoulders finish parallel to the pole which allows them to turn as though in a barrel lying on its side. This allows them to keep using the strength of both arms to add energy to the top of the jump, and since they have negative gravity at this point, every ounce of force counts. This is another position that confuses coaches coming from a Petrov perspective. The vaulter’s hips are separated from the pole and angled toward the bar, and yet they are still catching energy. It is the violent timing of the turn through the shoulders that is connecting their center of mass to the return of the pole. This position also allows the vaulter to have a very deep top end. The center of mass is not resisting gravity directly, but at an angle, which allows for greater height. Ideally the standards should be all the way back, and the pole should finish at an angle toward the bar. Mr. Dial believe that if we could put the standards at 100 we would jump higher, and he was right about everything else, so I don’t doubt him on this point.

I have got to get a film of Joe jumping high on here. The only two I have are of mediocre vaults at lower bars. I need some of the season he gripped 15’10” on a 17’4” 15.0 at 155 pounds. Peter McGuiness calculated his peak height at 20’2” on his clearance of 19’ to win the 87 National Championship. Here is the video of Buckingham that illustrates most of these positions. He was the prototype of the vault Mr. Dial developed. This is a relatively horrible vault. His step is a mile under, and his pole does not make it to vertical, but perhaps this illustrates my point better than a good jump. According to the Petrov model what he does in this jump is impossible.

http://www.youtube.com/watch?v=wooo4n8weU4

Please forgive the raggedness of this post. I just dashed it off. I will make corrections to it later if I need to. Also, it is an article of faith to me that if you are really passionate about something you will, at some point, talk total nonsense about it. I reserve that right and will be happy to be corrected where I am wrong.

[Pogo Stick]

Efficiency

For those of you who have access to the data, how about the ratio of body weight to pole stiffness given the same grip.

???????

Doug Balcomb
PV Coach, Colfax HS

I did, and the results are predictable:

Code: Select all

name      weight       flex      w*f
Sergei Bubka       80       10.6      848
Maxim Tarasov       81       11.2      907
Igor Tradenkov       78       11.7      913
Danny Ecker       78       11.7      913
Okkert Brits       88       10.4      915
Rodion Gataulin       81       11.4      923
Tim Lobinger       82       11.4      935
Dmitri Markov       80       11.8      944
Steve Hooker       83       11.5      955
Paul Burgess       83       11.6      963
Jean Galfione       82       11.9      976
Jeff Hartwig       92       10.8      994
Tim Mack         80       12.6      1008
Toby Stevenson       82       12.6      1033


Please note that lower number (weight x flex) is better because lower flex means stiffer pole. Grip is different for each vaulter.
3 Americans are at the bottom. Taller guys tends to use stiffer poles and flex is more in correlated with his weight.
FYI, the 6m table can be found at PHP main page, under Misc menu: http://www.polevaultpower.com/6mclub.php

Here is also grip/pushoff table for Tim McMichael (I added Joe Dial for comparison):

Code: Select all

Name   grip   push   grip/push
Joe Dial   480   136   3.53
Tim Mack   500   121   4.13
Tim Lobinger   503   117   4.30
Jean Galfione   505   115   4.39
Danny Ecker   505   115   4.39
Jeff Hartwig   508   115   4.42
Sergei Bubka   518   117   4.43
Steve Hooker   507   113   4.49
Igor Tradenkov   508   113   4.50
Rodion Gataulin   510   112   4.55
Okkert Brits   512   111   4.61
Dmitri Markov   514   111   4.63
Maxim Tarasov   515   110   4.68


This one is interesting. Tim Mack is now at top, Bubka in the middle and Tarasov at bottom. According to Tim McMichael that means Tim Mack was closer to optimal grip and pushoff ratio than Bubka. At the other side, Bubka made this up (and little bit more) by gripping 18 cm higher. So who is more efficient? You need fantastic technique, speed and strength for both. I don't know, I am and