does this seem right to you?

[spike gibeault]

the sense i am getting from this image is that they are telling you to pull down with your top hand!?

[achtungpv]

I believe that's the science behind the Texas Pole Vault Manifesto.

[rainbowgirl28]

They illustrate various biomechanical aspects of pole vaulting and were generated from data digitized from videotaped performances at the Summer Olympic Games of Barcelona 1992 by the ABAT project.

They must have been filming decathletes or something

[master]

the sense i am getting from this image is that they are telling you to pull down with your top hand!?

Do you have the paper that this is taken from? If so I'm sure it explains this drawing. It is virtually identical to Fig 4 of "Biomechanical Analysis of the Pole Vault", a paper published in the Journal of Applied Biomechanics 1994. I have a copy of that paper. If you have a copy of this one I would like to see it if possible. The image in your post looks like it says Copyright 1998 which is later than the publication I have.

To answer your question, they are not telling you to pull down. That is simply showing what the force exerted by the top hand would be if it were split into two components; the perpendicular (right angles to the pole) and the longitudinal (inline with the length of the pole). Of course these directions are relative to the position on the bent pole where the top hand grips the pole. To understand the idea of breaking a force vector down into two orthogonal components you can read about it here (among other places on the web.)

- master

[master]

I knew I remembered seeing that drawing somewhere on the web. It, and others are linked from this page.
http://www.cs.indiana.edu/~kinzler/pubs/pvfigs/

I wrote to Stephen Kinzler and he sent me the copy of the paper I have.

- master

[spike gibeault]

Yea, thats where i got it from MASTER.

[golfdane]

I believe that's the science behind the Texas Pole Vault Manifesto.

Yup, sure looks like it

Definately not the Adelaide/Petrov approach. I believe the print say 1993, and not 1998.

The forces indicate, that there is no emphasis on an active take off. Pulling down with top hand and pushing up with the lower hand promotes an early bend, but can lead to rejection (especially with a passive take off).

[AeroVault]

To answer your question, they are not telling you to pull down. That is simply showing what the force exerted by the top hand would be if it were split into two components

^ Right on, Master.

The picture is correct in that no matter how much you think you are pushing, there will be some perpendicular force on the pole after takeoff. It is not coming from your arms pulling, but from the weight and motion of your body. Notice the F_perp arrow is not pointing down, because the arrows are rotated to allign the longitudinal force with the pole. When you find the total force vector, it is nearly pointing into the pole which causes it to bend.

Think about it this way, has your top hand ever slipped, causing the top of the pole to recoil away from you? ... then you've seen what happens when you don't have this force on the pole.

At this point of the vault, the perpendicular component is probably very small compared to the longitudinal component, since the vaulter has barely left the ground, but I haven't done the calculations. The data came from the '92 Summer games, so I'm taking a wild guess that the athletes were pretty high caliber.

In fact, the figure is based off a variety of styles including the Petrov approach. Think about it for a while, but this is actually what happens when you vault correctly.

[altius]

The confusion is arising because the drawing has been done by a biomechanist who has no practical knowledge of the vault -a not unusual state of affairs unfortunately. Take a look at the position of the left heel which is still tucked under the butt -this IS where it should be at the instant the vaulter leaves the ground but not where it will be if the athlete is as high off the ground as shown here -it will have flicked forward by this point because the knee is a hinge joint -check any photo of Bubka at this point - preferably check the many photos of Bubka after you have purchased BTB2!!

Then take a look at the left -take off foot - it is pointing forward -a position it should not reach until much later in the whip swing -at the point shown it should still be pointing straight down - even slightly back afetr finishing a very powerful driving take off.

However with those points in mind the diagram does represent the forces which a vaulter like Bubka would begin to apply immediately they swing on the pole in the second phase of energy input -the centripetal force of that swing is enormous and contributes greatly to the bending of the pole and moving it forward in this phase - remember at take off Bubka tried to leave the ground with an unloaded pole.

The picture is likely to further clouded if the author threw all the vaulters into a composite because while the Petrov model vaulters tried to leave the ground with an unloaded pole - the great majority of the rest would have been actively loading the pole before they left the ground - the much favoured "Cannon" approach to the vault..

So once again our friends the biomechanists have clouded the water - as they have been doing ever since the flexible pole appeared. Suggest you read read C7 of BTB2 - it may clarify there issues.

Incidentally there is no Adelaide model -only the Adelaide approach to teaching the Petrov model.

[altius]

I should have added that the forces shown only begin to operate IF and WHEN the vaulters actively swings on the pole -a swing that should continue into inversion with the body as extended as possible. If it is a passive hang, very little force will be generated - and if the athlete tucks the force generated will be curtailed -or at least minimised.

There - that should put the cat firmly among the pigeons -or should I say it will open up a can of worms!

[golfdane]

I would still say, that the vertical force of the lower hand is far to strong (more than just bracing the arm), and IMHO contitutes an effort to provoke flexing of the pole (and some of the other figures suggests, that the free take-off just isn't there). I assume that the length of arrows compares to the force.

Can of worms ain't bad..... if you are going fishing

The biomechanical figures originates from videoanalysis of the Barcelona 1992 Olympics. Bubka did not qualify for the final. Won by Tarasov, Trandenkov second.

But Alan is right in the notion, that biomechanics didn't understand the physics involved. If this was the Petrov model (meaning, that biomechanics understood the Petrov model then), would the gravitational pull not be active just after takeoff (if indeed the takeoff was active). IOW, just after takeoff, would the hands exert an upward (from the active takeoff) and forward (from the speed of the run-up) going force on the pole.

http://www.cs.indiana.edu/~kinzler/pubs/pvfigs/31.gif

[AeroVault]

IOW, just after takeoff, would the hands exert an upward (from the active takeoff) and forward (from the speed of the run-up) going force on the pole.

Before the pole tip hits the back of the box, yes. After that it gets complicated. I would agree that even as the pole starts to bend you are still rising from your own energy and pushing the pole, but this figure is trying to show a bit further in the vault where the vaulter is now hanging from his top arm beginning to swing.

And you have to be careful with nomenclature. The figure is not showing a downward force or upward force, only perpendicular to the pole where the top hand grips.

I'll update this post later to include the figure with the total force vectors instead of just the components. It might help to see what each hand is actually doing during this phase. If someone else can beat me to it, please do.