Push off

[KirkB]

DJ,

... but in the vault you have the "lift" of the pole that is "lightening" the load so to speak... so it doesn't all have to be or seem to be muscle.. sometimes when you "feel" it too strongly it took too long and you will "fall" off the pole instead of "fly"...

Well, I'm saying that no matter how much the pole is lifting you, you still need to EXTEND as vigorously as you can. The net effect of the pole recoiling and you extending gives you the resultant pushoff (bar distance above your grip).

Little lift + little extension = bad.

Little lift + vigorous extension = muscling up (only good to recover from a poor vault ... but it may be tough if the pole's already ahead of you).

Big lift + little extension = bad ("riding the pole" - leakage and lost opportunity to add more energy into the system).

Big lift + big extension = WR!

I had big lift + big extension. I didn't set any WRs, but it was only because I wasn't a sprinter. The technique was there.

... of course way back in the early seventies we keep thinking you had to "rockback" and wait for the pole.. but when Earl, Dave Roberts and Tully came along we saw that the physics would dictate an "active" continuous swing action so you were not "dead weight' on the pole.

Even today, the "rockback" is the tell-tale of the drive vault model.

You've mentioned many times that Mike Tully considered the pole as a highbar. This is definitely Petrov model (before Petrov!). This continuous swing action that you speak of is correct, if you include the extension action that I speak of. Semantics, I guess. It's a swing/extension action, like on the highbar.

... not being dead weight on the pole is one of the reasons i am very emphatic about a "impulse" at the takeoff.. just as in the long jump... to do this “move” (jump/impulse) you cannot have a long last step or be "reaching" at all... you need a penultimate to do it correctly.. and you need to run correctly to have a penultimate. …

I get that. In fact, my takeoff was one of my strengths. I could jump - I just couldn't run. Maybe my running TECHNIQUE wasn't so bad in my prime, but the SPEED wasn't there. I'm certain that I did the penultimate and the takeoff better than most - by a long shot.

You mentioned long ago that "I must have had something" that put me into the elite class. I did have a very good takeoff. In fact, I often saw faster runners just let the pole pick them off the ground, rather than JUMPING off the ground. They didn't get that "lift" that you speak of - the start of the upwards momentum towards pushoff. I'd rather have a bad run and a good takeoff than a good run and a bad takeoff.

Good run + good takeoff + big lift + big extension = WR!

That is why it is very difficult to talk about one “phase” of the vault without bringing in points from the continuous chain… and the continuous chain starts with the run and not at takeoff.

I get that now. In my day, I didn't get that. Heck, we didn't even know what a "Reverse C" was or what a "Continuous Chain" was. That's actually why I call my "C" a Jump-to-the-Split - because I had to call it SOMETHING! (And by the way, I'm referring it to a position that you pass THRU - there should be no pause in the "C"). But without the hindsight of the past 36 years, there was no one to tell us that the Continuous Chain started at the top of the runway. I thought it started after the Split! I get that now!

... and just a note on the discus analogy.. the front foot "block" in the javelin and discus is simular if not the same "physics" as the pole tip planted into the box ...

OK, I see now that the analogy includes the ENTIRE swinging/extending motion from the moment when the pole hits the box. (Just before, actually, to include the takeoff.) At first, I thought you were talking about just the extension part of the vault, but especially after emphasizing the lift you get on takeoff as part of that, I see it more clearly now. That makes the analogy even better!

Kirk

[Tim McMichael]

I think efficiency can best be measured by a ratio of speed at takeoff and height of bar cleared. Extreme push off comes into play from the Oklahoma tradition only because of the fact that very short vaulters cannot grip as high as very tall ones. The physics get prohibitive in a hurry when an athlete 5' 8" or shorter tries to grip much above 16'. For a smaller athlete to compete on a world class level, the vault must be very efficient, and this will by necessity be expressed in push off distance. We discovered that push off could be increased far beyond what was widely considered possible, thus allowing us to compete when grip height was so significantly limited.

I believe Altius is right that push off alone is not a great indicator of efficiency because an athlete can simply lower their grip and push off farther on the same pole. There are a lot of variables involved in this that I will not go into, but from personal experience I can say that when my jump as working well I would clear the same bar with a 15' 10" grip as I would with a 15' 3" grip, just a lot less often. Every vaulter must find the right ratio of grip to push off that is most efficient for them.

Joe Dial 15' 9" grip 19' 6.5" vault.

To correlate to the list from the original post.
173 cm tall, 136 cm Push off

[Pogo Stick]

I think efficiency can best be measured by a ratio of speed at takeoff and height of bar cleared. Extreme push off comes into play from the Oklahoma tradition only because of the fact that very short vaulters cannot grip as high as very tall ones. The physics get prohibitive in a hurry when an athlete 5' 8" or shorter tries to grip much above 16'. For a smaller athlete to compete on a world class level, the vault must be very efficient, and this will by necessity be expressed in push off distance. We discovered that push off could be increased far beyond what was widely considered possible, thus allowing us to compete when grip height was so significantly limited.

I believe Altius is right that push off alone is not a great indicator of efficiency because an athlete can simply lower their grip and push off farther on the same pole. There are a lot of variables involved in this that I will not go into, but from personal experience I can say that when my jump as working well I would clear the same bar with a 15' 10" grip as I would with a 15' 3" grip, just a lot less often. Every vaulter must find the right ratio of grip to push off that is most efficient for them.

Tim, you just mention something important: optimal ratio of grip to push off.
The problem with speed, grip, flex, push off, etc. is that their relations are not linear. Engineers like me know very well that non-linear systems and equations are real pain in a** and are often impossible to calculate without simplifications. Each parameter and ratio has some optimal value range and maximizing each variable does not necessary guaranty maximal end-result.
You can only try to optimize few parameters the most important for you, and hope all other will stay within reasonable limits and will not affect main goal: jump higher. People who jumped 6m or more did that on different ways: griping anything from 5.00 to 518, with pole flex 10.4 to 12, last 5m speed 9.5 to 9.9, and take off from 110 to 121. It is try-and-error game - there is no magic formula.
By the way, a pendulum is classic example of non-linear system and resolving that problem includes knowledge of elliptic integrals (bad cousins of surface integrals - my nightmare at university).

Joe Dial 15' 9" grip 19' 6.5" vault.

To correlate to the list from the original post.
173 cm tall, 136 cm Push off

That's amazing! Relatively to his height this is 22 cm (8") more than Tim Mack who is the first on the list.

[dj]

Good morning

Hey Tim.. it’s actually your “style’ of jumping that had some of the good “physics”, of the points I’m trying to make.

First, if I only had the Data that Peter McGinnis first gathered from the vaulters (buried somewhere in a file in my barn in Florida.. where even my wife couldn’t find it)… I could put some numbers, from 8 vaulters of the time, to some of this discussion. I did a CPA style data sheet with all the individual data lined up across the page. Of the dozen or more entries for each athlete only 3 or 4 items even made a difference… among the 8 elite vaulters, short, tall, fast slow.. Pretty or ugly.. ; )

Since I can’t do that i just have to tell the “tell’ the way I remember it.

First I told Mike if he jumped the way Jeff Buckingham was jumping, 5-7/5-8 compared to 6’4 he might have a chance to beat Bubka. If not be happy with second or hang it up. He asked Jeff to come into the stands after Jeff was out of the competition at the meet indoors in LA. I let them talk and would only throw in a comment here and there, depending on if I wanted Jeff’s comment on a specific area.

One special place was the takeoff. Tully was of the “school’ that you hold the pole as high as possible at the plant and run horizontally off the ground. I wanted an “attack” or as I have stated before, an “impulse”. I know and knew from the long jump that you can jump further if you attack at the takeoff. Of course the speed has to be kept at the maximum but long jumping further usually means you applied more force on that jump. The pole vault is no different as to the physics. You apply more force by using “speed” or technique. Proper creation of force also leads to proper transfer of this force. Mike’s “running of the ground” was not creating the most force or allowing for the best transferring of that force.

Why do we need to create the most force? Hand grip.. I don’t think Mike or Earl had ever gripped over 16 feet until 83/84. and I know they were not the first Americans.

And I need to pause.. what does this have to do with “fly away”? If you don’t have the correct input at the plant/takeoff you will have extreme difficulty getting a maximum result off the top..…

watch a skateboarder on a ramp or a snowboarder in a pipe… or a motocross rider (me) on the jumps… another item here.. sorry to inject some many thoughts but any one part of the vault cannot be viewed in isolation. Even the “curve’ on the ramp, or pipe, or the mounds of dirt in motocross have to be “setup” right for the proper “transfer of momentum.”

That’s why the trajectory in “fiberglass - bending pole” pole vaulting has to be a part of the overall consideration. That trajectory plays to the correct “transfer of momentum”. Correct “transfer of momentum” is the only way, just as in the discus and javelin, that you can throw the implement or the “body” in the vault, the maximum above or away from the release point.

And when we open that thought… we can see why Linthorne’s paper raised to many questions without considering physics and made assumptions ...takeoff angle for example.. is created by a “jump” or some intent by the athlete!!?? all things being equal the takeoff angle is simply created by the “flex”, stiffness or design of the pole... based on the application of the forces transferred at the plant.

Many of his premises don’t really follow the flow and transfer of momentum of the bending pole vault, fiberglass vaulting.

Petrov mentions the ‘dynamic’ of planting the pole with the hands going up “AS” the vaulter contacts and starts the push from the ground with the takeoff foot. This is a dynamic, impulse, “punch” that adds force or momentum to the pole plant with a much better result than “reaching high and waiting for the takeoff foot and the pole to contact the runway and the box. Mike eventually started calling this dynamic.. his “linebacker meeting the running back head on at the line of scrimmage!” I guess he watched the super bowl the weekend he came up with that one. But his point was if you are the linebacker and the pole is the running back you had better assume the position and ‘attack” or you will be left on your.. tush.

The one most glaring item on the charts that I made from Peter's data was Tully’s last two steps were long and longer…6’9” and 7’1”… the dynamic takeoff vaulters, Bubka included, had short long.. 7’1 (penultimate) and 6’9” (TO)… we spent 1983 and 1984 changing that.. even though Mike was still determined to “not jump” we gave him the “impulse” he needed to have the body moving “up” at the takeoff so the speed of the swing was faster and the fly away more dynamic and consistently higher.

Lot at the vaulters of today.. .. the ones that have a long last step, and incorrect penultimate (I see it with the women a lot) swing, go flat at the top and “flag’ over the bar.

Mike refused to “jump” and I think some coaches sometimes put to much emphasis on a jump. That’s where teaching a good penultimate plays a roll in getting the athlete closer to a correct takeoff. It depends on the athlete I have seen some vaulters, world class, jump “to much” and not have a feel for the vault. And what does a jump have to do with the ‘fly away”?

That “impulse” needs to be there so you can have a “continuous chain” and a chance to “pop” from the top.

Sorry to drag this out… but I could add more "stories" about the "impluse" that adds to the “continuous chain” that allows the vaulter to fly from the top… but i'll give it a rest.. it's time to go to the track and to apply the theory to the reality........

If you re-read what Petrov has said... it is clear, to me at least, he is presenting the best way (free or free-er takeoff.. high dynamic plant.. correct transfer of momentum) to maximize the force in...

Bye

dj

[Tim McMichael]

I never, ever tried to jump up off of the ground. But I did everything possible to get as tall as I could coming into takeoff. And I attacked as hard as possible. Dean Dial did not want me to jump up. He had me consider whether or not at 5' 8" I was ever going to be able to win a jump off of the ground contest with the likes of Earl Bell. The answer of course was a resounding no. Then he taught me to consider the vault the task of storing energy into a system as opposed to an assisted high jump. This concept was fundamental to my understanding of the vault.

[altius]

With regard to the original post - I would just like to point out that you are almost certainly basing your conclusions on dodgy data.

[Carolina21]

Someone with stronger physics knowledge may be able to do a more sophisticated version, but I thought I would take a stab on a slow afternoon.

I thought this might be interesting, or at least stir a good debate. I completely agree with Tim's idea that speed into takeoff compared to height cleared is the true indication of efficiency, not push off. You could simply never raise your grip and get on crazy stiff poles to improve push.

Anyways Using some equations I found off the internet (yikes) I used the 6m chart and added a few more equations and lines. To determine what their speed alone should allow them to clear. You could determine velocity needed to clear the bar since we don't go straight up and down, but actually keep moving forward, but seems like overkill since it is likely same for most jumps, and I don't believe changes who is more efficient.

Height = Velocity ^2 / 2* Gravity Acceleration (correct?).
So here is an example

Assumptions:
1) V^2 = Last 5m MPS Squared
2) Gravity = 9.8 mps
3) We want to know how far the athlete moves the COM, so to simplify I divided their height by 2. (Sources say mens COM is .56 of their height, .5 is close enough I think)

Tim Mack Example

Height = V^2 / 2 * Gravity
Height = 9.5 ^2 / 2* 9.8
Height = 90.25 / 19.6
Height = 4.605m

Now this represents how much he should be able to move his COM.
If his COM is starting at a position 1/2 his height, then it starts at 1.88m / 2
So he should be able to move his COM from .94m (and raise it 4.605m) to a height of 5.545m.
Being that Tim is a very efficient vaulter he is adding energy post takeoff. He actually moved his COM 6.01-.94 = 5.07m
So that means he cleared (5.07-4.605)/4.605 +1, to calc the percent of his potential or in his case 110%.

So using good 'ol excel



Now the first thing that caught my eye was Bubka being at the bottom..... I am not trying to in any way to say he was ineffiecient it was just the way the numbers worked out. Also I do not know how acurate these MPS readings were and they can greatly change the results even if they are 0.1 MPS off. Still, it was interesting to note if you took Igor and gave him Bubka speed he could clear with his efficiency: 6.47m

[KirkB]

Carolina, nice work!

Your last 2 rows are (12) Bubka at his WR bar clearance, and (*) Bubka assuming a 6.40 bar clearance.

You have sorted the rows of this grid in order of "% of Potential Height" (i.e. "efficiency rating" - using the formula you described).

Not to be picky, but if the CoM is at .56 body height, then there's no reason to round to .50. It doesn't complicate the formula - in fact, it might make it more precise. Conversely, % of Potential Height is clearly not significant to 2 decimal places (else the results would be closer to our contemporary thinking). I would knock off at least the 2 decimal places. Until the % of Potential Height matches our contemporary thinking a little better, even expressing it as a whole number is "inaccurate".

Likewise, Potential Height is not accurate to 3 decimal places. The precise values in this grid should be retained in order to prevent rounding errors. It's just that when they're displayed, they should be rounded to reflect only significant digits. But for consistency, perhaps display this one to 2 decimal places ... if only to match the other columns (to make the grid more readable).

Perhaps our resident engineer - Pogo Stick - can take the Speed and Height - and try to correlate them into a formula that results in the highest PRs having the highest efficiency ratings? After all, Pogo, with only 2 variable, this should now be a piece of cake for you, shouldn't it?

Bubka is the fastest of the 6.00m club members, but - with the assumption that efficiency correlates (according to your formula) to takeoff speed and athlete height - he has the lowest efficiency ranking.

Even at his theoretical best ... 6.40 ... according to the formula ... his efficiency is APPARENTLY still lower than Stevenson, Mack, and Tradenkov.

Intentionally stirring the pot here ...

This is counter to our contemporary thinking. Only one of the follow 2 statements can be true ...

1. Bubka was the most efficient member of the 6.00m club.
2. Bubka was the least efficient member of the 6.00m club.

They cannot both be true.

I conjecture that ...

1. Bubka was likely ONE of the most efficient members of the 6.00m club.
2. Takeoff speed is an extremely significant factor in the determination of a vaulter's potential PR.
3. There are other factors at work that have not been included in the formula yet.

These "other factors" might include ...

The issue of "bar clearance efficiency" and "CoM compared to Cross Bar Height". Who's to say how much bar clearance each of these athletes made on their PRs? Some may have slipped over, rattling the bar, and others may have cleared it by a mile. (I don't know how to measure that, short of frame-by-frame video analysis. And even then, you'd need a consitent close-up angle for each vaulter (a bar-cam). This is data that isn't readily available for many of these PRs.) And in a jackknife style clearance, the CoM can pass UNDER the bar, so matching the Cross Bar Height to the peak of the CoM path is fraught with inaccuracies.

There's 2 other factors that are in what I consider my area of expertise ...

1. Speed of the Whip.
2. Speed of the Extension.

The first one is significantly more determinant to efficiency than the second, but they're both important (per my dialog with DJ). Carolina, put together and weighted (somehow) with takeoff speed, these other 2 speeds should model the "% of Potential Height" better than your basic formula.

Let's ignore the second one (it's harder to measure and less important), and focus on the first one for now ...

1. Analyze the vaulter's swinging action frame-by-frame.
2. Catch the frame BEFORE his body is aligned top-hand-to-trail-leg-toe. (Frame #2) This is deemed to be not only the middle of the "Whip", but also the easiest to capture consistently from one vault to another.
3. Catch the frames immediately preceding and succeeding this frame. (Frames #1 and #3)
4. Measure the distance his trail-leg ankle moves between Frame # 1 and Frame #3.
5. Measure the height of the athlete (in Frame #2). Use this to scale the vids. Since the vaulter's height is a known constant, you can then compute the ACTUAL distance that his trail leg ankle moves.
6. Using the camera shutter speed (time between frames), compute the speed of the trail leg.

Now back to our resident engineer, you now have 3 unknowns to resolve in the formula. Discarding the issue of "bar clearance efficiency" and "Speed of the Extension" (to simplify the formula), whatever formula forces the highest PRs to the top of the grid should be the best determinant of "% of Potential Height".

Thus, the "% of Potential Height" should highlight the OTHER factors (factors OTHER than what are already accounted for in the formula) that are more difficult to understand or measure.

Again, I'm no expert when it comes to physics, so what I'm suggesting is merely to inspire the resident PVP experts into resolving an answer to this puzzle.

Kirk

[dj]

good morning.

good stuff Carolina21... really good

When I first sifted throw the data from Peter… these are the things that “stood out” speed of the takeoff.. the height of the “reach” as compared to the height of the vaulter… (Bubka was higher than Tully and Tully was three or 4 inches taller… my first thought was arm length! But that was not the reason.) the trajectory.. the amount of pole bend compared to the “speed’ of the vault from toe leaving the ground to maximum CM over the bar.

The best trajectory was IN and UP… like a half pipe… swinging the whole time as fast as you could… Mike and Earl called it “getting in the pocket” I said NO.. going through the pocket.. if Mike felt a little “sink” when his back was “flat” to the runway he knew he had better not hesitate that it was time to come on back.. as Petrov said “cover the arc of the pole” and pull and shoot from the “high bar”.. I know he pulled like Kirk describes it because the trigger finger on his right hand, top grip hand, would “bust-split open” from the force. He had it taped all the time.

Again this next bit is not exactly on fly away but has to do with trajectory.. and trajectory is totally about getting your mass as high above the bar as possible………

In the 1970’s a Russian “scientist’ by the name of Oslon..? did and article called Oslon’s Pipe Design Theory.. It was a comparison of the takeoff and trajectory in the high jump between the old style “straddle” High jump (Valrie Brummell, Pat Mazdorff.. etc.) and the new style “Flop” that was setting world records and taking over the event. It had long been thought or agreed to that a straight takeoff leg would allow the body to be “pitched’ higher than a bent takeoff leg. Oslon went about proving that a trajectory in the shape, (path) of a half pipe was much more efficient in the “transfer’ of energy from horizontal to vertical. Part of his proof was blasting smoky air into pipes.. one with a ninety degree “L” shape angle and another set with a curved “half pipe” angle. When he blasted the same amount of air into each set of pipes the curved pipe produced the highest “return”. We know and have to understand there is always going to be energy lose when going from horizontal to vertical. The most efficient way to do this is the key. Oslon’s theory was that the ninety degree turn actually “absorbed” part of the force because it hit it “head on” where as the curve allow for a “flow’ or better transfer.

This is where we have to understand that the trajectory and the takeoff angle matter when we want to get the maximum height above the bar.

In and up.. allows for better transfer.

To big of a pole absorbs too much of the “force’… plus it takes the mass “UP” to quickly creating an additional lose of force.. and slows the penetration, which in turn stops the “continuous chain” movement which leads to a low return off the top.

dj

[KirkB]

DJ, our replies to Carolina crossed in the mail!

... Too big of a pole absorbs too much of the “force’… plus it takes the mass “UP” too quickly creating an additional loss of force.. and slows the penetration, which in turn stops the “continuous chain” movement which leads to a low return off the top.

Correcting a couple typos to make your quote above a bit more readable ...

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 traveling a further distance, which will take more time. Due to gravity pulling you DOWN, time is of the essence! Thus, the optimal path will not be "crushing the pole" (too big of a bend), nor will it be to stiff of a pole (too much leakage due to abrupt changes in direction).

When you think of it, this is the advantage of fiberglass over steel.

With steel, the abrupt angle changes immediately upon takeoff caused tremendous leakage (loss of energy). So much so that your grip needed to stay low, and your jump (or impulse as you call it) on takeoff needed to be strong.

With fiberglass, the absorption of energy into the pole meant that it didn't leak - it could be used later, as the pole uncoils. It also meant that you could grip higher, without stalling or fear of pulling your shoulder out of its socket.

DJ, by comparing a stiff fiberglass pole to a soft fiberglass pole, and also by stressing the importance of the impulse on takeoff, you're talking about these same laws of physics. It all makes perfect sense.

Kirk

[KirkB]

In my post immediately before DJ's, I forgot to mention that as long as you're going to measure the speed of the whip by frame analysis, you might as well measure the vaulter's horizontal speed at the instant before takeoff in the same way - rather than taking an average speed over the last 5.00m. After all, it's your ACTUAL speed on takeoff that's important - not your AVERAGE speed down the runway.

Also ... it would be more difficult to measure, and it would depend on a free takeoff (and perhaps a higher speed camera), but you might also measure your VERTICAL IMPULSE on takeoff in this same way. This adds to the complexity of the formula, but unless it's included in the formula, the "impulse" gets absorbed into the "other factors" category.

I agree on the importance of this factor with DJ. It's important enough to try to build into the formula if we're truly trying to measure comparative "efficiency" from one 6.00m club member to another. Actually, you don't need to measure only the vertical component. The ANGULAR distance traveled at the trajectory angle would suffice. Ideally, you'd want to measure the distance traveled between when the toe leaves the ground, and when the pole hits the box. That's why you'd need a very high-speed camera!

Kirk

[KirkB]

Hmm ...

Carolina, so the premise is that if you're 100% efficient, your speed at takeoff will predict your max CoM delta.

Something's wrong here ...

As you show, the 6.00m vaulters are all (apparently - according to your formula) ABOVE 100% efficiency, so the assumption is that they're ADDING additional (net) energy to their vaults.

But there's also the LEAKAGE factor - the SUBTRACTING (LOSS) of energy from their vaults.

The net of the additions and subtractions should yield their net efficiency %.

But as much as I agree that they're all exceptional athletes at ADDING more energy into their systems and minimizing leakage, I would have expected the net to be something LESS than 100%.

So I could be wrong, but I suspect that something's wrong in the formula.

It would be interesting to do this same analysis with elite high jumpers. It's a simpler formula, since the pole is eliminated. There's no complications of a double-pendulum swing, and no anchor to the ground for the duration of the jump (from takeoff to pole release).

So what would the predictions for % efficiencies be for elite high jumpers' be, given their PRs, taking their speed at takeoff, and translating that to their vertical CoM deltas? How close to 100% efficiency does the WR-holder get?

I cannot imagine their % efficiencies to be more than 100%, as there's no way to add energy past the HJ takeoff point (when the toe leaves the ground). There can only be LOSS of energy due to the conversion of horizontal runup speed to vertical HJ speed. Some of DJ's ideas re a curved pipe vs. a square-elbowed pipe come into play here. The HJ CoM path cannot possibly be as smooth of a curve as the PV CoM path ... thus HJ has to be more inefficient. But how much?

I just think that this knowledge might provide us with some insight into the proper PV formula.

Kirk