Trail Leg- Tuck or Petrov?

[Tim McMichael]

I've been trying to stay out of this debate because I think I've said about all I can, and I have no interest in convincing anyone, especially since I don't know what is best myself. I am at least several months, if not years, away from understanding enough to say anything definitive. The reason I can't stay away from this one is that the defenders of the straight leg are saying that all the physics are on their side, and I don't believe this to be the case. In the interest of putting accurate information out there and nothing else, here is a paragraph from my Oklahoma Pole Vault Manifesto that can be found here.

http://polevaultpower.com/forum/viewtopic.php?t=11053

I have no desire to write it again or expand on it at this point. My Redneck Pole Vaulter post has more readers anyway. LOL.

Anyway here are my thoughts on the physics of the tuck. Please notice that this is only true if the tuck happens after the swing is as long and fast as it can be.

Another difficulty is the idea that the tuck robs the swing of energy. This is simply not true. The law of conservation of angular momentum dictates that a rotating object does not lose energy when its radius is shortened. It merely gains speed as it swings around its axis. The swing reaches maximum speed at the instant a straight line can be drawn from the top hand through to the foot of the trail leg. At this point, the body is as long as it can possibly be and has attained all the speed of rotation it is going to. After this, nothing can be gained by attempting to keep a rigid body and a straight leg. Shortening the radius of the swing by pulling the trail leg in after this point does not lose energy. The radius of the swing is shortened, and the velocity of the rotation is increased, but the energy remains unchanged, except for what is lost to gravity and friction.

[vault3rb0y]

The energy remains unchanged if the speed of the swing stays proportional to the length of the swinging axis. But what if you can increase the speed of the swing without shortening the axis? Also, 99% of high school vaulters probably misunderstand that as meaning that "as soon as my swing goes under my body, i can bend my knees and shoot at the bar, and i wont lose any energy" or some even worse representation.
I believe in what you are saying, and know that the only reason you brought your knees up was because you were on such stiff poles, pushing 46", that if you DIDNT shorten your axis you had no shot of timing up with the pole. It would have been extremely difficult to keep your trail leg straight and swing with your same velocity. But it would have put more energy into the pole as far as i can see. Bubka didnt have a problem timing up because his core was probably the strongest in the world, and he held 5.18 and not below 5.00, again due to his physical characteristics, which might have allowed him a little more time to finish his swing. If you dont know the best model, tim, im no where CLOSE to knowing the best model. All i know is that keeping a straight trail leg will add more energy than a bent one, IF and ONLY IF their velocities are the same.

[lonestar]

I never took a physics class in my life, but it would seem to me that keeping the trail leg long would keep your center of gravity lower, thus moving the pole forward easier (the metronome/pendulum effect). Once your center of gravity became equal to your point of support (when your back is parallel to the ground) it wouldn't matter, and you could tuck as much as you want to finish inverting faster. If you tucked before that though, you would speed up rotation from the shoulders, but by raising your center of gravity you would take pressure off the pole and it would recoil prematurely and the pole would leave without you. I think you have got to have your center of gravity above your hands before the pole recoils, or you're missing a ton of energy return at the top. I see it all the time with tuck-and-shooters whose hips are well below their hands when the pole begins to unbend - they are always trying to play catch-up with their center of gravity/hips well below their point of support/hands and the pole is straight before they're ready to fly-away, where Bubka was already flying away before the pole even straightened because he had such massive energy returns. It would be like an old-fashioned catapult...if you place the rock on the very top end of the arm, it would throw it farther than if you set it a few feet farther down. Bubka was able to keep the pole bent for longer with the extended trail-leg, thus buying him precious fractions of a second to get his center of gravity as high on the end of that catapult as possible. I see that the tuck-and-shoot proponents theory is that they have to tuck to accomplish the same goal, speed rotation to be able to get on top of it, but by raising your center of gravity too soon in the vault, it takes pressure off the pole, it recoils prematurely, and the opposite effect happens where they're late. Some just could time it up better than others (Okies and Frenchmen!).

[Tim McMichael]

I never took a physics class in my life, but it would seem to me that keeping the trail leg long would keep your center of gravity lower, thus moving the pole forward easier (the metronome/pendulum effect). Once your center of gravity became equal to your point of support (when your back is parallel to the ground) it wouldn't matter, and you could tuck as much as you want to finish inverting faster. If you tucked before that though, you would speed up rotation from the shoulders, but by raising your center of gravity you would take pressure off the pole and it would recoil prematurely and the pole would leave without you. I think you have got to have your center of gravity above your hands before the pole recoils, or you're missing a ton of energy return at the top. I see it all the time with tuck-and-shooters whose hips are well below their hands when the pole begins to unbend - they are always trying to play catch-up with their center of gravity/hips well below their point of support/hands and the pole is straight before they're ready to fly-away, where Bubka was already flying away before the pole even straightened because he had such massive energy returns. It would be like an old-fashioned catapult...if you place the rock on the very top end of the arm, it would throw it farther than if you set it a few feet farther down. Bubka was able to keep the pole bent for longer with the extended trail-leg, thus buying him precious fractions of a second to get his center of gravity as high on the end of that catapult as possible. I see that the tuck-and-shoot proponents theory is that they have to tuck to accomplish the same goal, speed rotation to be able to get on top of it, but by raising your center of gravity too soon in the vault, it takes pressure off the pole, it recoils prematurely, and the opposite effect happens where they're late. Some just could time it up better than others (Okies and Frenchmen!).

Okay, I'm going to get hammered for this, but here is how it worked for us. Most athletes who tuck and shoot flag out and their velocity is next to nothing at the top of the jump, but this is because their takeoff is bad, and they tuck at the wrong time. We could push off so far because our center of gravity was actually much lower through the second half of the jump. A vaulter who extends early puts their center of gravity at the top of the pole just like a catapult, but an athlete who tucks has their hips below their hands for almost all of the jump like a trebuchet. The trebuchet was a siege engine that replaced the catapult because it was vastly more powerful. Someone recently built one as a physics experiment and they threw a car over two hundred yards.

http://blog.makezine.com/archive/2007/0 ... het_v.html

As you can see, the weight hangs down below the lever arm, which allows the arm to move to vertical with much greater speed than it would if the car were attached to the very top of the arm. An athlete who slams a lot of power into the pole with a great takeoff and swing and then tucks at the right time releases the pole to accelerate toward the bar - not prematurely, but after the swing has put as much power into the pole as it can. Their center of gravity is lower and, therefore, there is more pole speed at the top of the jump. The vaulter is attached to the pole with as much of a taut connection as the rope on the sling of a trebuchet. This is why their center of gravity is launched above their hands. Because "the kinetic energy of an object is proportional to the square of its speed," this means that even a small increment of pole speed has an enormous effect on the energy available at the top of the vault. Combine this with the fact that elite vaulters who use this method learn to apply force with their arms at the top of the jump to add even more power and you have the secret of a 50" push off.

Check this out as an example. Buckingham gets hammered under, and his pole does not even come close to finishing vertical, but he still has the pole speed to make it over the bar.

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

Remember, Buckingham was only about 5'7" tall. By everything that has been said about the limitations of the tuck and shoot, what he does in this video should be impossible. You can actually see him catch an extra surge of energy over the bar. Stop the video when his feet reach the height of the bar and ask yourself if, from this position, it is possible to make it over. Then watch him blow over it. I want to submit that there may be some misunderstanding of this technique when the outstanding results obtained by the few athletes to maximize its advantages contradict all of the conventional wisdom about what should be possible. As I said at the outset, the principles of physics are not all on the side of the Petrov model.

I'm cringing in anticipation of the beating to come.

[vault3rb0y]

Ive always looked at the vault in terms of adding the most energy into the pole, period. not positioning your center of gravity to recieve this energy at a certain point in the vault!

You continue to open my mind and make me think more deeply about the intricacies of the vault Tim...

Obviously there are advantages and disadvantages of both techniques. Maybe it comes down to physical abilities and limitations, and what parts of the vault an individual vaulter can exploit for the most energy.

[lonestar]

Okay, I'm going to get hammered for this, but here is how it worked for us. Most athletes who tuck and shoot flag out and their velocity is next to nothing at the top of the jump, but this is because their takeoff is bad, and they tuck at the wrong time. We could push off so far because our center of gravity was actually much lower through the second half of the jump. A vaulter who extends early puts their center of gravity at the top of the pole just like a catapult, but an athlete who tucks has their hips below their hands for almost all of the jump like a trebuchet. The trebuchet was a siege engine that replaced the catapult because it was vastly more powerful. Someone recently built one as a physics experiment and they threw a car over two hundred yards.

http://blog.makezine.com/archive/2007/0 ... het_v.html

As you can see, the weight hangs down below the lever arm, which allows the arm to move to vertical with much greater speed than it would if the car were attached to the very top of the arm. An athlete who slams a lot of power into the pole with a great takeoff and swing and then tucks at the right time releases the pole to accelerate toward the bar - not prematurely, but after the swing has put as much power into the pole as it can. Their center of gravity is lower and, therefore, there is more pole speed at the top of the jump. The vaulter is attached to the pole with as much of a taut connection as the rope on the sling of a trebuchet. This is why their center of gravity is launched above their hands. Because "the kinetic energy of an object is proportional to the square of its speed," this means that even a small increment of pole speed has an enormous effect on the energy available at the top of the vault. Combine this with the fact that elite vaulters who use this method learn to apply force with their arms at the top of the jump to add even more power and you have the secret of a 50" push off.

Check this out as an example. Buckingham gets hammered under, and his pole does not even come close to finishing vertical, but he still has the pole speed to make it over the bar.

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

Remember, Buckingham was only about 5'7" tall. By everything that has been said about the limitations of the tuck and shoot, what he does in this video should be impossible. You can actually see him catch an extra surge of energy over the bar. Stop the video when his feet reach the height of the bar and ask yourself if, from this position, it is possible to make it over. Then watch him blow over it. I want to submit that there may be some misunderstanding of this technique when the outstanding results obtained by the few athletes to maximize its advantages contradict all of the conventional wisdom about what should be possible. As I said at the outset, the principles of physics are not all on the side of the Petrov model.

I'm cringing in anticipation of the beating to come.

Very interesting Tim! Never had heard of a trebuchet. Almost a hammer- throw concept in a way. I can't counter that logic, except to say that "what is technically desirable must be physically possible." Right Alan?

[Tim McMichael]

Okay, with that last post, I've either said something very smart or very stupid, and I don't know which. And Altius, Agapit, et al. I am still teaching Petrov whenever appropriate. I am about ready to concede that the differences in my theory are due more to individual limitations than to some alternate principle - but not quite yet. I still do not believe I would have jumped as high as I did with anything other than what I describe in my manifesto. And it may very well be that the principle of keeping the center of gravity low during the last half of the jump is a sound innovation.

One of the things that leads me to doubt myself is that I am rebellious and hardheaded enough to propose it simply because it directly contradicts what almost everyone believes and teaches. Another factor in presenting this observation (and this is the first time I have done it in public) is that it is safe. I have never seen an athlete who uses this method land anywhere but the center of the pit. There are several reasons for this that I won't go into right now, but the clip of Buckingham that I posted is as illustrative of this fact as anything I can think of. Were he fully extended before the pole stopped bending on that jump and foolish enough to finish the vault, he would not have made it to the pit. I have never seen anyone else clear a bar off of a jump where the pole came so short of vertical.

I am also irreverent enough to point out that not all of the effects of Petrov's influence have been positive. Not because the model is wrong, but because its application has been haphazard and incomplete. One of the most damaging effects of the universal admiration of Bubka and his jump is that many coaches and athletes have developed a fixation on being inverted as early as possible. This is the most striking aspect of his jump and it has become an end in itself instead of the result of everything that comes before it. I have found that an early inversion is often taught without any reference to the fundamentals of the approach, pole carry, and plant that make the whole thing work. An athlete who flips to inversion off of a low, decelerating, and ugly takeoff is asking for nothing but trouble. I cannot count the number of times I have seen a vaulter with a horrible run and plant miss a bar and nearly land in the box only to be told that he did not invert quickly enough. Just a few weeks ago I was forced into the painful responsibility of telling another coach that he was about to get one of his athletes killed doing this.

Also, in instances where an athlete's established form will work i.e. double leg, drive and tuck. I feel I will be doing a disservice to, for example, a senior in college, if I cost them two years to change form. My life as a journeyman coach rarely allows me to deal with beginners from the ground up. Often I am called on to patch up a jump that has gone terribly wrong, and I find that a thorough understanding of other effective methods is essential. I do not, and will not, say that an athlete can vault any old way they please, and I know that one of Altius' primary concerns is safety. Petrov's model is as safe as can be, and safer than 90% of what I see too often taught, but it must be built upon the foundation of a proper understanding of the run and takeoff.

It is absolutely essential that bad ideas not be taught. What I talk about may not be the best thing, but it will always be safe, and it will always be effective. It is my solemn responsibility to the sport to see that this be so. Within that context, however, a lot of what I say here is as much an invitation to conversation as it is a pronouncement of truth. I hope, however, that I have shown that there is a such thing as a tuck and shoot that is based on some understanding, however incomplete or mistaken, of the physics of the vault. And I am certain that a lot of what is said about it is not based on a rigorous study of why it works. People simply say it cannot be used to jump high, and when they see a clip of Joe Dial simply shrug their shoulders and put it down to superhuman strength, or worse, simply ignore the evidence of their own eyes. When I see a very high vault with a form that I don't think can get it done (Stacy Dragila) instead of ignoring it I take it as evidence that there is something I don't understand, and then I try to understand it. It is the dismissive tone of a lot of the criticism I face that goads me into rambling and over long posts like this.

[altius]

I know all about trebuchets! As an amateur military historian I have visited many of the castles in Europe that they were used against.

However even that thought is not going to entice me back into this debate - I have set out my stall with the new BTB and there comes a point where in the end you have to go with what you believe and leave it at that - as my old gran said - "A man convinced against his will remains of the same opinion still".

So believe what you will TIm, I am no longer going to try to change your mind. Too busy getting myself fired up to rewrite my first book -Play practice, a games approach to teaching and coaching sport". Know any good sites where I can start debating in this area -would you believe that games are even more badly taught than the pole vault??

[Soar Like an Eagle]

Okay, with that last post, I've either said something very smart or very stupid, and I don't know which. And Altius, Agapit, et al. I am still teaching Petrov whenever appropriate. I am about ready to concede that the differences in my theory are due more to individual limitations than to some alternate principle - but not quite yet. I still do not believe I would have jumped as high as I did doing anything else. And it may very well be that the principle of keeping the center of gravity low during the last half of the jump is a sound innovation.

One of the things that leads me to doubt myself is that I am rebellious and hardheaded enough to propose it simply because it directly contradicts what almost everyone believes and teaches. Another factor in presenting this observation (and this is the first time I have done it in public) is that it is safe. I have never seen an athlete who uses this method land anywhere but the center of the pit. There are several reasons for this that I won't go into right now, but the clip of Buckingham that I posted is as illustrative of this fact as anything I can think of. Were he fully extended before the pole stopped bending on that jump and foolish enough to finish the vault, he would not have made it to the pit. I have never seen anyone else clear a bar off of a jump where the pole came so short of vertical.

I am also irreverent enough to point out that not all of the effects of Petrov's influence have been positive. Not because the model is wrong, but because its application has been haphazard and incomplete. One of the most damaging effects of the universal admiration of Bubka and his jump is that many coaches and athletes have developed a fixation on being inverted as early as possible. This is the most striking aspect of his jump and it has become an end in itself instead of the result of everything that comes before it. I have found that an early inversion is often taught without any reference to the fundamentals of the approach, pole carry, and plant that make the whole thing work. An athlete who flips to inversion off of a low, decelerating, and ugly takeoff is asking for nothing but trouble. I cannot count the number of times I have seen a vaulter with a horrible run and plant miss a bar and nearly land in the box only to be told that he did not invert quickly enough. Just a few weeks ago I was forced into the painful responsibility of telling another coach that he was about to get one of his athletes killed doing this.

Also, in instances where an athlete's established form will work i.e. double leg, drive and tuck. I feel I will be doing a disservice to, for example, a senior in college, if I cost them two years to change form. My life as a journeyman coach rarely allows me to deal with beginners from the ground up. Often I am called on to patch up a jump that has gone terribly wrong, and I find that a thorough understanding of other effective methods is essential. I do not, nor will not, say that an athlete can vault any old way they please, and I know that one of Altius' primary concerns is safety. Petrov's model is as safe as can be, and safer than 90% of what I see too often taught, but it must be built upon the foundation of a proper understanding of the run and takeoff.

It is absolutely essential that bad ideas not be taught. What I talk about may not be the best thing, but it will always be safe, and it will always be effective. It is my solemn responsibility to the sport to see that this be so. Within that context, however, a lot of what I say here is as much an invitation to conversation as it is a pronouncement of truth. I hope, however, that I have shown that there is a such thing as a tuck and shoot that is based on some understanding, however incomplete or mistaken, of the physics of the vault. And I am certain that a lot of what is said about it is not based on a rigorous study of why it works. People simply say it cannot be used to jump high, and when they see a clip of Joe Dial simply shrug their shoulders and put it down to superhuman strength, or worse, simply ignore the evidence of their own eyes. When I see a very high vault with a form that I don't think can get it done (Stacy Dragila) instead of ignoring it I take it as evidence that there is something I don't understand, and then I try to understand it. It is the dismissive tone of a lot of the criticism I face that goads me into rambling and over long posts like this.

Tim, I agree with you on the different techniques.

Joe Dial was 5’9â€

[rainbowgirl28]

If a coach interprets, Beginner to Bubka technique properly, the technical approach is great, but coaches need to really understand the concept of the run, plant, and take off before swinging on the pole.

If they read the book, pay attention, and apply it, they will understand those principles.

[Tim McMichael]

I know all about trebuchets! As an amateur military historian I have visited many of the castles in Europe that they were used against.

However even that thought is not going to entice me back into this debate - I have set out my stall with the new BTB and there comes a point where in the end you have to go with what you believe and leave it at that - as my old gran said - "A man convinced against his will remains of the same opinion still".

So believe what you will TIm, I am no longer going to try to change your mind. Too busy getting myself fired up to rewrite my first book -Play practice, a games approach to teaching and coaching sport". Know any good sites where I can start debating in this area -would you believe that games are even more badly taught than the pole vault??

I have no doubt that is true, and when you publish it, I want a copy. Alan, I hope I have made it no secret how much I admire and am indebted to your work. And BTW you already have changed my mind. Ask anyone who has known my coaching over the last several years and you will appreciate how much.

[Tim McMichael]

If a coach interprets, Beginner to Bubka technique properly, the technical approach is great, but coaches need to really understand the concept of the run, plant, and take off before swinging on the pole.

If they read the book, pay attention, and apply it, they will understand those principles.

Without a doubt. Beginner to Bubka more than adequately deals with these concerns.