Push off

[dj]

Good morning

Yes, there's an optimal path that your body must follow which can't have any "square corners". But also, it can't deviate TOO far from a direct line from takeoff to bar clearance, else you're travelling a further distance, which will take more time.

Kirk

what we are missing is “longer and faster”… why can't it be longer and faster? Because of the bend qualities of the pole. If the pole is not to “stiff” the vaulter will travel the “IN” distance of the trajectory faster.. not only moving the cord closer to vertical but ‘swinging” in the process which “adds” to the energy input.

While going “directly” at the bar, the way of the steel vaulters, takes away the benefit of “shortening the radius” gain by using fibreglass.

In other words a 16-4 four grip shortened to a 12 foot grip should take the same “swing” force to move to vertical as a 12 foot grip on a none bending steel pole…

The big advantage is when you get the fibreglass pole to vertical it has regained it’s length and you are working with a 16-4 grip.. when you get the steel to vertical you are still only working with a 12 foot grip….

Bamboo had the same advantage.... they just could not be bent enough without the chance of breaking.. plus finding your “flex’ number in the swamps of Florida, (John Pennell) meant fighting the mosquitoes, snakes and gators…..

Food for thought..

dj

[Carolina21]

Hey Kirk/DJ ,

I have updated the sheet with your suggestions, .56 COM and round Efficiency %'s. When I actually think about it your COM is probabaly even higher than .56 since your arms are above your head at takeoff, and not by your side. Also your knee is raised up. It might be closer to .6 or .65 at takeoff, any thoughts?

I think the problem you have with 100% and higher numbers comes more from the fact that efficiency in this case is not the right word. The problem I think is that 100% efficient would be subjective; we would have to determine what the most amount of energy an athlete could add during the swing, and the least they could lose. Then we would factor this in, and have a base to compare against.

My final number is just a percentage showing the expected height achieved from physics based on the initial velocity input into the system, compared to the actual height achieved by the vaulter.

Secondly, we would suspect this number to be greater than 100% since when clearing a bar you COM actually passes under the bar due to the piked position we enter in clearance (so I hear). And the fact we add energy with the swing (also as stated above your COM is probably higher than .56 at takeoff). I think these two (three) factors are great enough to allow us to go above 100%. So I think the formula I used itself is correct, maybe just not a complete description of what is happening.

Like I said before this was simplified and an idea to start with, and maybe someone on this board with some better data and formulas can produce more robust results, or can give me those formulas and data and I will do it. I thought it might be a good first step to truly coming up with a measurable way to compare vaulters post takeoff. I think push off doesn't work as a true measure, it can be manipulated. I think this is closer since in the simplest form we are trying to move our COM higher than our competition, whoever does this the best through a combination of height (how tall you are), runway speed, swing energy added, etc wins. We really need more vaults to declare anyone more efficient than someone else, and we would have to be sure of the speed they actually transferred into takeoff is the same as their last 5m running speed, or close enough not to matter.



I would like to end with the reason I still believe Bubka was most efficient. Efficiency after takoff is only one part. The ability to run 10mps (in a good position) with a pole through your plant required a whole different type of efficiency and skill and he did that better than anyone. Maybe his technique post takeoff was the best and most efficient and maybe it was only as good as other top guys (that can be debated on here apparently forever), but as a total package he was the best thus far.

[KirkB]

... While going “directly” at the bar, the way of the steel vaulters, takes away the benefit of “shortening the radius” gain by using fibreglass. ...

Yes to your entire post. I wasn't arguing for a steel vault style technique (a MUCH more direct line from takeoff to release). I was arguing for a "happy medium", wherein you didn't lose the advantage of the higher grip afforded fiberglass vaulters (for the reason you explained), yet you didn't "crush the pole" too much.

On my best jumps in 1971, I was close to that happy medium. In my entire 1972 season, I crushed the pole too much because I didn't realize the inefficiencies involved in not keeping your momentum going in a continuum in an upwards direction.

CRUSHING THE POLE is a PASSIVE action! That's because you're "waiting for the timing" of letting the pole get to max bend, rather than continually applying body actions that will keep you going up-up-up and back-back-back (the opposite of flagging out).

That's all.

Kirk

[KirkB]

I have updated the sheet with your suggestions, .56 COM and round Efficiency %'s. When I actually think about it your COM is probabaly even higher than .56 since your arms are above your head at takeoff, and not by your side. Also your knee is raised up. It might be closer to .6 or .65 at takeoff, any thoughts?

It depends on what you're trying to measure. Personally, I'd ignore your CoM whilst you're reaching your arm and driving your lead knee on takeoff. That's because I'd consider that part of your EFFICIENCY. If you make the ASSUMPTION that the CoM includes this for ALL vaulters, then you're making a false assumption, since we all know that it's a flaw to NOT reach/drive on takeoff - but many vaulters (especially beginners and intermediates) do this. So IMHO, if you truly want to measure EFFICIENCY, then you should take the lower CoM - just BEFORE the reach/drive on takeoff.

I think the problem you have with 100% and higher numbers comes more from the fact that efficiency in this case is not the right word. The problem I think is that 100% efficient would be subjective; we would have to determine what the most amount of energy an athlete could add during the swing, and the least they could lose. Then we would factor this in, and have a base to compare against.

My final number is just a percentage showing the expected height achieved from physics based on the initial velocity input into the system, compared to the actual height achieved by the vaulter.

Right. I agree with that, but it still begs the question of why Bubka's at the bottom rather than at the top. Taking either his REAL WR of 6.15, or his ESTIMATED hip height (CoM?) of 6.40 on his "best" jump, he's still at the bottom. So something's wrong here. If our contemporary thinking is that Bubka was hands down the most efficient vaulter in history, then why is he not at the top? It has to be the formula that's wrong. No?

Secondly, we would suspect this number to be greater than 100% since when clearing a bar you COM actually passes under the bar due to the piked position we enter in clearance (so I hear). And the fact we add energy with the swing (also as stated above your COM is probably higher than .56 at takeoff). I think these two (three) factors are great enough to allow us to go above 100%. So I think the formula I used itself is correct, maybe just not a complete description of what is happening.

OK, but still ... what's wrong? It doesn't add up!

I think push off doesn't work as a true measure ...

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.

In hindsight, Pogo did stir the pot and get us all thinking and collaborating, so this thread has turned out quite good, IMO. And I don't think we're done yet, because I suspect that when Pogo chimes back in, he'll be wearing his engineering hat.

I would like to end with the reason I still believe Bubka was most efficient. Efficiency after takoff is only one part. The ability to run 10mps (in a good position) with a pole through your plant required a whole different type of efficiency and skill and he did that better than anyone. Maybe his technique post takeoff was the best and most efficient and maybe it was only as good as other top guys (that can be debated on here apparently forever), but as a total package he was the best thus far.

Right. So how do we model that?

Or better yet ... how do we put it in a can and sell it?

So far, the answer to this dilemma has eluded us. We can't even put it into a theoretical formula that matches real life!

Kirk

[dj]

hye kirk

i think the crushing comes from not having the up "impluse" and the continuous fast swing..

i think Tim Mack's 5.90 jump that i have spoken about often, had the best trajectory, the speed of the swing..(1.43 seconds compared to the first Bubka jump I timed at 1.47 seconds) and the “impulse.” Yet that jump was termed by many, to be a “pole squashier” but It was not even close… because of the speed of the swing and the height above the grip and of course the”impulse.”

That 5.90 Tim Mack trajectory was pretty much identical to the first Bubka trajectories, where he was gripping the top of a 5 meter pole.. and bending them over 30%.. I actually drew the trajectories on tracing paper and matched up the correct proportions.. (which I had done with Earl’s by projecting film on the wall when he was a 17 footer.) so I could see if they were different and where..

I have since (actually ladyvol did it for me on Dartfish) taken another 5.90 jump by a different vaulter, gripping the same grip as Tim.. hitting the same MID as Tim and about the same height as Tim but faster than Tim, overlaid them..to see if and where the differences where. Style, timing, pole bend, physics ..etc..

Interesting comparison… Even though the other vaulter was faster than Tim, he did not clear the bar by as much as Tim, he had slightly different timing from takeoff to max bend and “back flat to the runway” position.. he also had a slight “delay” at maximum bend but finished above the bar at approximately the same time as Tim. Which meant he had to speed the rotation (tuck slightly) after the slight delay to finish in the same amount of total time..

So I had a “continuous chain” ..vaulter a..Tim ………over laid with a none continuous, vaulter b.. slight tuck vault… with timing and comparisons of the pole bend to boot.

dj

[Andy_C]

That's a very nice spreadsheet Carolina!

Though I think there are other factors that need to be taken into account. Specifically with the COM, variations in body types can be really important. Take a look at Bubka, he's all legs! So I don't think you can apply a single number like .56 to all of the vaulters, you'd have to look at each one and make measurements if you want to have the up-most accuracy. There are also other issues like what if somebody nailed a pre-jump?

Also, are there numbers for Steve Hooker? Just curious.

Again, I don't think it's perfect, but it's very good nonetheless.

[KirkB]

i think the crushing comes from not having the up "impluse" and the continuous fast swing..

In my case, I always had the "up impulse" - a very powerful jump on takeoff. But I swung my trail leg so darn fast (after lifting it UP and BACK, to make it even faster), after PAUSING in the Split position for a moment , that I had no trouble crushing a 195 pound pole. (I was 172 pounds, and ran the 100m in 11.4 - once!) By pausing in the Split, it caused me to sink FORWARDS towards the bar too far, instead of contiually rising (as in my better vaults). My CoM should have followed a more direct path towards the bar.

However, I do agree that many vaulters crush the pole by not jumping off the ground as vigorously as they should.

Kirk

[dj]

hey

i agree.. the pause was most likely the cause.. if you swing "through" fast... the trail leg goes from below horizontal to the runway.. which is still creating a "bending" force... to above horizontal which will start to take pressure off of the pole so it can "un-bend" eaiser.. there is no time for a "static" sink.. the sink Mike felt at the maximum bend was just a little "dip" and go..

lare

dj

ps sorry didn't have time to spell check...

[Pogo Stick]

Hey Kirk/DJ ,
I would like to end with the reason I still believe Bubka was most efficient. Efficiency after takoff is only one part. The ability to run 10mps (in a good position) with a pole through your plant required a whole different type of efficiency and skill and he did that better than anyone. Maybe his technique post takeoff was the best and most efficient and maybe it was only as good as other top guys (that can be debated on here apparently forever), but as a total package he was the best thus far.

Sorry, kid's schedulle was very hectic this weekend and I had no time to reply before. I will summarize few things and will not reply to individual posts.
Your formula is special case of transformation kinetic energy to potential energy where no losses occur. And lot of losses occurs during the: friction, pole impact with box, losses in vaulter's body during takeoff, losses in pole, etc.
As dj noticed, you need to take into account horizontal distance. COM path (trajectory) is not straight vertical line but complicated 3D curve. This trajectory is different for each jump and depends on many variables. Tim, Kirk and dj described that very well (pole type and bend, grip, swing, etc). Also, it is possible to add energy in the pole-vaulter system after takeoff because human body can produce energy (think swing).
I have no picture of COM trajectory, but Alan has nice one in BTB2, page 43, figure 7.5. The components are:
1) Horizontal: from take off point to standards
2) Vertically: from approx. half vaulter's height to little bit bellow bar
3) "3rd dimension": Looking from the back. If you ever landed at side edge or outside the pit, you are aware of 3rd dimension.

Available data:
for 1) there is no available data, or at least not known to me
pretty good approximation can be used for 2)
for 3) this is more or less straight line, perpendicular to ground or close to perpendicular. We can ignore this one and look at pole vaulting as 2D problem.

I will make some simplifications and assumptions that will not produce 100% accurate results, but will show some relationships between horizontal and vertical speed components.
To calculate horizontal component we need to know take off point and vaulters height with right hand up. I am 177 and I can reach around 230 so I would assume that someone who is 10cm taller can reach 10cm (2.40).
We can calculate takeoff point from vaulter's height with one hand up and pole grip (Pythagoras Theorem). Don't forget on box depth (20 cm).
Tim Mack is 188 cm tall, I assume he can reach with hand up 11 cm higher than I can (230+11=241cm). Add 20 cm for box and this is 261cm. His grip is 500 so takeoff point is square root from (500*500 - 261*261) which is equal 426cm.

Let's simplify calculus little bit more and substitute complicated COM trajectory with straight line. Let's also assume that the higher COM point is at bar height. We have another triangle:

Now we can calculate COM path assuming COM position at half vaulter's height. Again Tim Mack is 188cm, his COM is at 94cm and bar height is 600cm. COM path is hypotenuse of the triangle and is equal 654 cm. Here is a complete table, sorted by COM path:

Code: Select all

Name   PB (cm)   Height (cm)   Pole Grip (cm)   Speed   hand up height   take off   COM path
Sergei Bubka    615   183   518   9.94   236   450   682
Dmitri Markov    605   181   514   9.84   234   447   673
Maxim Tarasov    605   194   515   9.75   247   440   664
Rodion Gataulin    602   190   510   9.75   243   437   661
Jean Galfione    600   184   505   9.68   237   435   660
Steve Hooker    600   187   507        240   435   659
Igor Tradenkov    601   190   508   9.47   243   435   658
Okert Brits    603   196   512   9.74   249   436   658
Jeff Hartwig    603   194   508   9.73   247   432   657
Tim Mack    601   188   500   9.50   241   426   654
Tim Lobinger    600   190   503   9.62   243   429   654
Danny Ecker    600   193   505   9.71   246   429   653

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.
The actual COM curve lengths are bigger than in my example (remember, this is a very strange curve), and this fact just emphasize importance of speed.

Also Alan is right - the accuracy of collected data is probably questionable. Maybe few 6m jumps were properly measured using high speed cameras, photo cells, markers and other equipment. If you are using your home camcorder, TV or movie projector to count frames and calculate speed the error margin can be one frame or 1/30 of second. That means if you are calculating the speed over last 5m, instead of 10 m/s you can get anything from 9.4 m/s to 10.6 m/s and that is a huge difference. Vaulter's weight can also vary few pounds during competition. Data about grip are probably most accurate, but inch or two inaccuracy is also possible.

[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. The one flaw in my "theory" can be bar bar clearance: taller guys will need more time/speed/force to rotate himself around bar.

In hindsight, Pogo did stir the pot and get us all thinking and collaborating, so this thread has turned out quite good, IMO. And I don't think we're done yet, because I suspect that when Pogo chimes back in, he'll be wearing his engineering hat.

Small disclaimer first. I am IT guy with B.Sc. of Electrical Engineering. During my University years I hooked up on computers and ended in IT field. I am still addicted, but I am trying to become clean. At university we got very good training in fundamental and applied science. Lot of my friends and colleagues from same T&F club went to Faculty of Physical Education. I learned from them about training process, biomechanics, anatomy and physiology and I taught them physics, mechanic and computers.

[Pogo Stick]

That's a very nice spreadsheet Carolina!

Though I think there are other factors that need to be taken into account. Specifically with the COM, variations in body types can be really important. Take a look at Bubka, he's all legs! So I don't think you can apply a single number like .56 to all of the vaulters, you'd have to look at each one and make measurements if you want to have the up-most accuracy. There are also other issues like what if somebody nailed a pre-jump?

Also, are there numbers for Steve Hooker? Just curious.

Again, I don't think it's perfect, but it's very good nonetheless.

I find today the following article on net: "POLE VAULT AS DOUBLE PENDULUM AND PENETRATION". Here is a link: http://www.asrigas.gr/doc/arthra_doublependulum_170603.doc

In this article the scientists from Aristotelian University of Thessalonica, Greece discuss about almost everything we are talking here. It is just 6 pages long and worth to read. I found 3 intriguing citations I'd like to discuss.

1. Factors affecting performance in pole vault:

According to Muthiah (1986) success in pole vault can be attributed to various parameters of the vault:
1. Up to 40 % is determined by run up speed.
2. Up to 40 % is determined by technique.
3. Up to 15 % is determined by the upper body strength.
4. Up to 5 % is determined by jumping ability.

What do you think? Are these ratios close to your experience? If 40% is determined by technique what to do? It is relatively easy and known how to improve and measure speed, upper body strength or jumping ability, but how to measure improvement of technique? Perhaps the best advice will be go to local gymnastic club and ask their coaches for help.


2. Push off comparison of rigid and fiber vaulters:

As it can be seen in Table 1, the improvement in performance from 4,76m (with rigid poles) to 5,45m (with flexible poles) up to 1980 was 0,69m. Schmolinsky (1983) concluded that the improvement was mainly due to the higher grip of 0,63m (90,9 %) whilst only 0,06m (9,1 %) was due to clearance efficiency or catapulting the flexible pole.

Wow! I heard many time that push off improvement was smaller than grip increase, but this is the first time I saw the numbers. The data are little bit old and probably are little bit better for fiberglass vaulters today. At the other side, probably pole technology has added few inches there.


3. About pole stiffness:

The results showed that:
1. Best results were achieved with the appropriate stiffness of the pole.
2. In the case of the softer pole, with all the other parameters staying the same, the CM of the athlete reached to 0,56m “in pit” and 0,43m lower than the actual vault.
3. In the case of the stiffer pole the CM of the athlete reached 0,68m higher but it was 0,73m “out pit” than the actual vault. With the stiffer pole the athlete’s CM was higher but at the same time he hadn’t reached the pit, the penetration was poor (Braff & Dapena, 1985). In both cases of simulation, neither with the softer pole nor with the stiffer pole, results were not as good as with the appropriate stiffness of the pole.

This shows that you need optimal pole flex, not the stiffest one you can jump. I would say that the same is with grip and take off angle and lot of other parameters.

[KirkB]

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. ...

I see your premise here Pogo, but have you considered this? ...

The CoM of a taller vaulter on takeoff is a distinct advantage, since it reduces the angle of the pole towards vertical. Also, the taller vaulter is already "higher" up toward the bar before he even leaves the ground. This much we agree on, right?

Now to invert on the pole, you're saying that he will gain yet another advantage because he's "taller in his handstand - just before he releases the pole".

The difference that I see is that the advantage on takeoff is clearly the vaulter's luck on how tall he is. That's in his genes, and short of growth hormones, there's not much a shorter vaulter can do about that.

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?

Kirk