And so I reiterate. People with these systems, and indeed when talking about the pole vault in general when it pertains to a successful vaulter or successful system, can and do have a tendency to make claims based on "physics" which are in fact based on gross errors in the understanding of physics, i.e. you cannot have a "Total Energy" curve and leave out pole energy! , and then go on to make claims about what the vaulter is doing, and what advantages the system contains.
Point 1. The graph is a correct representation of the energy exchanges of the VAULTER! It is not a graph of the energy transformations within the total system. It does not purport or claim to be for the total system.
Will, Get real! The situation was a world championship!
How do you collect the data on every vaulter’s pole and the pole changes from jump to jump and then to have access to all these vaulter’s poles before or after the competition and measure their energy storage and recoil capacities. This is required to be able to do what you are criticising, namely the energy exchanges within the total system of pole plus vaulter!
The vaulter on the other hand can be studied by means of high speed cinematography with minimal invasion of, or interference with the competitor or competition. The evidence of the measurable changes in the vaulter’s recorded motion did enable the energy exchanges of the vaulter to be validly obtained and the data properly presented in graphical form.
Point 2. Will, look again at the graph and read it properly from a physics perspective. Your interpretation of what the graph shows is, in my opinion, incorrect.
Point 3. Here is where I think you may be making a mistaken interpretation. Look at the kinetic energy curve of the VAULTER. Does the vaulter’s kinetic energy curve, or does it not, show a low point coincident with MAXIMUM Pole bend?
Thereafter the vaulter’s kinetic energy curve rises until it reaches a peak a short interval before the pole is straight and then declines at a steady rate until pole release.
Surely this rise MUST be due to recoil work done on the vaulter by the recoiling pole and the vaulter doing muscular work against the recoiling pole! (I am an old fashioned Classical Physics Newtonian!).
After pole release the vaulter’s kinetic energy then shows a steady decline, at a lesser rate until the vaulter’s centre of mass reaches peak height!
Note that vaulter’s kinetic energy is still above zero at this point.
This is because the vaulter still possesses constant horizontal translatory energy to which must be added his constant rotational kinetic energy. There is a portion of kinetic energy transformation from vaulter vertical kinetic energy into the vaulter’s potential energy increase following pole release as he loses vertical velocity. Therefore the kinetic energy curve will show a small decline which of course it does.
Now, let’s back track to the rise in the vaulter’s kinetic energy immediately following maximum pole bend. The rise can only be possible due to energy input from two possible sources, the vaulter or the release of the strain energy stored in the pole or both!
Clearly, in this case, it is both energy input sources!
Surely the vaulter must have received some of the stored energy from the pole and this is indirectly revealed in the graph shown.
However there is, in my view, the necessary and sufficient data upon which to draw the appropriate inference that the kinetic energy gain of the vaulter immediately following maximum pole bend is due to vaulter muscular effort in conjunction with some additional energy from the recoiling pole being transferred to the vaulter.The problem of disentangling how much kinetic energy increase in the vaulter is from the pole and how much from the continuing muscular work of the vaulter on the recoiling pole cannot be fully resolved from this graph.
Will, if this is what you want to know the research effort required is prohibitive and calls for carefully controlled research under laboratory conditions with scientific control and manipulation of the independent variables. The data gathering in 3 dimensions, using motion recorders operating at quite high sampling rates, 3-D force and torque transducers in the pole, a force platform under the vaulter take-off and an instrumented planting box, getting athletes to participate, sample size, funding expertise and time make the whole effort questionable. Particularly when what we want to know as coaches is answerable empirically and is not rocket science!
To do this in a competition (see point one) requires the pole to be instrumented with torque and force transducers, as well as strain gauges and the outputs of these sensors telemetered and synchronised in real time to recorded motion of the vaulter on the pole. Feasibility of doing this in a World Championship, practical and economic challenges aside, is still remote.
The methods used by the researchers who performed the study from which this data is obtained were independent scientists appointed by the IAAF.
Here is the reference to the study: GROS, H.J./KUNKEL, V. (1988): "Biomechanical Analysis of the Pole Vault", ... World Championships in Athletics Rome 1987,
Point 4. In the graph the Total Energy of the vaulter is the SUM of the Kinetic and Potential Energy of the vaulter
as determined from data in frame by frame analysis of the vaulter’s motion obtained by cinematographic recordings from a number of cameras.
Point 5. The kinetic energy was calculated by the researchers by summing the translatory kinetic energy plus the rotational kinetic energies of the individual body segments of the vaulter (body segmental method). This method allowed the full summation of the vaulter’s total energy transformations throughout the vault.
Point 6. The actual total energy gain due to the muscular work of the vaulter is the difference between total vaulter energy at take-off and total vaulter energy at pole release which is about 1450 to 1500 Joules.
This MUST be so because the vaulter acting alone forced the bend in the pole thereby storing some strain energy some of which was recouped in the pole recoil phase. This is an interaction which must have some energy loss that is not doing useful work. Useful work is defined as the energy used to cause a force to displace an object (force x displacement) or a torque causing an object to undergo angular displacement (torque x angular displacement). Note: if there is no force or torque induced object displacement then in physics by definition no work has been done! The vaulter will be expending some muscle energy in stabilizing some parts of the body which then do not move (isometric active muscle action) and hence no mechanical work has been done. Not all of the vaulter’s muscular effort can be transformed to do mechanical work and thus the vaulter must be also performing “physiological work” for no measurable mechanically observable output. In this regard the energy graph actually underestimates the physiological work demand and input from the vaulter.
Point 7. Despite what you keep insisting I have not really found anything that you have had to say so far invalidating anything I have presented in regard to the vaulter’s energy exchange shown in the graph I put up.
When the issues you have with “Bubka’s semantics” and as yet to be demonstrated physics errors, myths, half-truths, and hyperbole of “Petrovians” are put aside, there is in fact considerable shared ground. Niggling away though is the issue of your understanding of how the “Petrov-Bubka Model of the “Free Take-off” may or may not optimise the capacity of the vaulter to produce equal to or even greater effective pole bend than that possible by inducing some pole bend before take-off.
You have presented anecdotal evidence by referring to a number of French, Russian vaulters, including Bubka, taking off with obvious pole bend before the take-off foot has left the ground. The question has to be asked was the vaulter in question trying to minimize pole loading resistance or optimizing pole bend before take-off? Ultimately we have to ask the vaulter to ascertain their intention. Intention is a “psychological” factor and on this there is agreement.
Your critique is of the physics basis of the two techniques and has not as yet become clear to me. I can only speak for myself here.
Your practice as a coach and the general comments you make convince me that after toing and frowing on the “swings and roundabouts” your “intuition” is to lean towards the Petrov-Bubka Technical Model.
But please give us the physics rationale that backs up your intuition and why Petrov’s explanations are inadequate from your physics perspective?
The value I take from your contributions so far is the critical point that coach and vaulter have to understand and sensibly assess the potential gains and losses of these two possible take-offs.Let’s move the discussion on and examine critically and specifically what your “critique” shows to be the deficiencies in the Petrov-Bubka Physics principles applied in “finishing the take-off” and how and why superior results can be, or not obtained by pre-bending the pole whilst the vaulter is still in the propulsive phase of ground contact!
I make no claims to the specific expertise of a physicist, but if my interpretation of the data shown in the vaulter energy exchange graph is insufficiently exact or wrong I would appreciate having my errors pointed out.
As other contributors point out we all need to be on the same page if we are to get anywhere!
I am hopeful that one of the outcomes might be to settle the push-pull issue.
I optimistically hope that if the discussion continues, the push – pull following the take-off can be explained and illustrate that Petrov and Roman Botcharnikov are not as far apart conceptually as we are led or would like to believe!