Pole vault research paper: influence of pole plant timing

[julienfrere]

Hi there, I just made a quick research on Pubmed (http://www.ncbi.nlm.nih.gov/pubmed/22534564) to check if there was a new research paper about pole vaulting. And below is what I found:

Journal of Biomechanics. 2012 Jun 1;45(9):1625-31.
Influence of pole plant time on the performance of a special jump and plant exercise in the pole vault
Schade F, Arampatzis A.
German Sport University of Cologne, Institute for Biomechanics and Orthopedics, Germany.

Abstract
The purpose of this study was to examine the effect of the timing of the pole plant during the stance phase of the jump on the energy level of the vaulter/pole system at take-off for a special pole vault take-off exercise (Jagodin). We hypothesised that an earlier pole plant would increase the pole energy at take-off compared to the energy decrease of the vaulter during the jump and plant complex and so lead to a higher total energy of the vaulter/pole system at take-off. Six male pole vaulters experienced three Jagodins each with different pole plant time building three groups of vaults (early, intermediate, late pole plant). Kinematic data of vaulter and pole were recorded, as were ground reaction forces measured at the end of the pole under the planting box and under the take-off foot. These measurements allowed the energy exchange between the vaulter and pole to be determined. We found neither statistical significant differences in the mechanical energy level of the vaulter/pole system during take-off between the three groups nor a relationship between the timing of the pole plant and the energy level of the vaulter-pole system during take-off. We conclude that although the timing of the pole plant influences the interactions between the vaulter, the pole, and the ground, it does not affect the athlete's performance. Although a late pole plant decreases the loss of energy by the vaulter during the take-off, this is counterbalanced by a decrease in the energy stored in the pole at take-off.

That's very interesting, isn't it?

To read the paper, click here http://perso.univ-lemans.fr/~jfrere/

[julienfrere]

For me, this paper mainly shows two things:
1) that the pole plant time doesn't influence significantly the performance in pole vaulting since the overall energy of the vaulter/pole system is similar. There is a balance/compensation between vaulter's velocity during the last stance and the elastic energy stored in the pole depending on the selected pole plant time. A latter pole plant provides a better vaulter's velocity maintenance but lower elastic energy stored in the pole. Inversely, an earlier pole plant time allows to increase the stored elastic energy in the pole, but there is a higher decrease in vaulter's velocity at take-off.
2) that the pole plant time may be a parameter the coach can select to adjust the technique depending on the physical capacities of the vaulter. A fast athlete can for instance prefer a late pole plant while a stronger but slower athlete can favor an earlier pole plant.

For sure, this paper provide a strong scientific proof that the pole plant timing doesn't merit all of these topics that we can find on this forum , and that the V. Petrov's model doesn't allow the vaulter to benefit from a significant higher mechanical energy and pole vault performance.

Regards,
Julien F.

[coachjvinson]

"He uses statistics as a drunken man uses lamp posts - for support rather than for illumination."

On first glance, I have several questions about the limitations of what is being measured.
The experimental design takes four measures
velocity of the vaulter
force from a pressure sensor in the plant box
force from a pressure sensor at take off location
compression or bend of the pole

and has the following conclusions...

"The findings indicate that an earlier pole plant is related to an increase in pole energy
as a function of the energy exchange between vaulter and pole,
rather than the result of additional energy production... "

There is no additional energy, thank you Sir Issac Newton.

"An earlier pole plant increases the energy transfer to the pole,
but causes simultaneously a similar decrease in the vaulter’s
energy."

This is a subjective conclusion as the study does not measure subsequent swing velocities nor pole velocities: which are fundamental indicators of the vaulter's energy. It is only measuring runway velocity, the collision of the pole into the box and ground reactive forces (pressure on the pole) maintained during the Jagodin, the force of the TO foot on the pressure plate and the compression or bend of the pole.

I am certain that I can spend more time reading and evaluating the study; however, it's just not necessary given the study's limited applications and subjective nature in which you are trying to apply the data. I am certain there are possible objective merits of the study: possible, just not to the extent you are attempting to apply them.
Thank you for your post,
-V

[coachjvinson]

In the context of the experiment, early pole plant is defined as meaning-early in relation to the touchdown or footstrike of the takeoff foot and late pole plant is defined to mean - late in relation to the beginning of the touchdown or foot strike in the final step of the takeoff; the beginning of the take off impulse plantar flexion.

"...planting the pole near to the instant of touch-down, through to
planting the pole at the instant of take-off. The advantage of a
later pole plant has not been scientifically proven yet. An earlier
pole plant during the stance phase of the jump, for example, may
increase the energy transfer to the pole through muscular work
increasing the energy of the vaulter/pole system. However in
athletic jumps the total energy of the vaulter’s body decreases
during the stance phase of the jump."

"It should be noted that none of the subjects executed a pole plant
close to the take-off. Our findings reveal valid mechanisms of
interaction between vaulter and vaulting pole, therefore we do not
believe that pole plants close to take-off would have influenced our
findings fundamentally. A free pole plant, which is a plant that
occurs after take-off, was not executed either. It might be possible
that this variation in pole plant timing causes qualitative differences
in the interactions between vaulter, pole, and ground and could
therefore affect pole vault performance in a different way."

So, none of the vaulters were anywhere close to a plant ahead of the takeoff action or even close to the takeoff action.

What was variable and independently quantified was whether or not the vaulter was planting at the point of heelstrike/touchdown, which is synonymous with an early plant according to the experimental definitions, or at some point after the heelstrike/touchdown nearing the plantar flexion action of the take off, which is synonymous with a late plant according to the experimental definitions.

Again, in the published findings of the authors and designers of the experiment,

"It should be noted that none of the subjects executed a pole plant
close to the take-off... A free pole plant, which is a plant that
occurs after take-off, was not executed either."

Nothing even close to the take off action/impulse,
So when these guys/gals were vaulting and planting the pole, the pole was bending and their foot was either just contacting the ground or they were beginning to plantar flex, that's it. Oh yeah, they planted the pole, did not swing in the Jagodin, and their "Athletic Performance" was measured subjectively in a manner that may have some relevance, I'm certain. Currently, it's relevance simply supports the entire invalidation of any practical application of the presupposition of your positon.

"...none of the subjects executed a pole plant
close to the take-off..."

I am certain that I can spend more time reading and evaluating the study; however, it's just not necessary given the study's limited applications and subjective nature in which you are trying to apply the data. I am certain there are possible objective merits of the study: possible, just not to the extent you are attempting to apply them.
Thank you for your post,
-V

[coachjvinson]

I just could not allow the heresy to go unchallenged;

repent...

What the study does appear to state is that an early plant - planting close to or at a point near the heel strike - will bend the pole more at the expense of the vaulters energy as quantified in this experimental design.

"We hypothesize that an earlier pole plant during the stance phase of the jump will increase the pole energy at takeoff compared to the energy decrease of the vaulter and so lead to a higher energy level of the vaulter/pole system at take-off."

Their hypothesis under the experimental definition was that an early pole plant close to the moment of heel strike would load or bend the pole AND result in a higher level of energy of the vaulter/pole system at take-off.

"Therefore our hypothesis is rejected. The findings indicate that an earlier pole plant (close to the point of heel strike) is related to an increase in pole energy as a function of the energy exchange between vaulter and pole, rather than the result of additional energy production."

Their hypothesis was disproved and their findings indicated that a pole plant near the point of heel strike did in fact load and bend the pole more; However, the overall transfer of energy into the vaulter pole system was decreased and compromised.

The author went on to attempt to mitigate the results of the findings in some type of attempt to subvert the implication that the converse would indicate that a later pole plant in the experimental design closer to the model of Petrov, would in fact yield greater transference of energy into the vaulter pole system.

In fact, the more I look at the data, the more this experiment appears to support the Petrov model - looking at the charts of the data provided, their is a direct correlation between the timing of the pole plant with energy into the system: as the pole plant timing is closer to the take off (late in relation to the heel strike and closer to the point of plantar flexion) there is a trend of greater energy transference not only independently among the same vaulter but within the group as a whole.

Further, there is an indirect correlation between the load or bend of the pole and the take off time: the closer the pole plant to the point of takeoff, the less of a forced load or bend is placed on the pole.

Further, I would question whether the value placed on a huge bend into the pole represents a quantitatively large amount of energy transferred into the vaulter pole system as quantified within the calculations and definitions of this experimental design; basically, at what point is the bend a representation of a loss of transference instead of a representation of stored energy in which there is a functional transference of energy into the vaulter pole system.

Finally, as this experimental design limits the "Athletic Performance" to an equation which does not include all of the indicators of energy transference into the vaulter pole system, the findings are limited in application in respect to this aspect. Even still, the overall sum of energy transference into the vaulter pole system as measured and quantified by the experiment appears to support Petrov's Postulate: the closer the pole plant is to the take off impulse (late in this experimental design's definition), the greater the overall energy transference into the vaulter pole system.

The final quantitative analysis of the experiment appears to minimize this conclusion through the assignment of an arbitrarily large value of energy transference placed on pole load and bend which occurs when the plant timing correlates with the heal strike and the subsequent forced bend and diminished overall velocity of the vaulter. In practical applications it is apparent that this does not represent a functional energy transference into the vaulter pole system; yet, the experimental design places a significant value on this experimental group within the data collection through the calculation of the formula utilized to quantify the data measured to arrive at a singular value of energy transference. This aspect appears to impose a bias towards a greater load or bend in the pole than is functional or practical.

I am certain that I can spend more time reading and evaluating the study; however, it's just not necessary given the study's limited applications and subjective nature in which you are trying to apply the data. I am certain there are possible objective merits of the study: possible, just not to the extent you are attempting to apply them.
Thank you for your post.
-V

[coachjvinson]

"If we knew what it was we were doing, it would not be called research, would it?"

So, I have cut and paste a few images from the research to further demonstrate and clarify exactly what is being stated: as pointed out in the prior posts, the figure A is defined as an early pole plant, B as an intermediate pole plant, and C as a late pole plant. This points out the importance of the definition and application in terms between experimental settings and practical settings. Case in point, a coaching cue that I utilize and emphasize is to be early with the plant, because of the day to day interactions this is inferred to mean being early with the plant AND takeoff impulse/action: both are treated as one within our methodology. In the experimental context this is the opposite "late is early" and "early is planting at/near heel strike"

Within the experimental setting and as diagrammed below, the function of timing is an interrelationship between the sensor which times/senses heel/foot impact prior to take off and the sensor in the box indicating pole plant impact. Additionally, it appears that the diagram below does not accurately reflect the hypothesis nor the data in as much as the hypothesis and data both indicate a greater transfer of energy into the loaded/bent pole in vaulter A and a lesser degree of bent/loaded pole in vaulter C. I will expound on this idea in the next post (I can only include 3 images per post): further, I suspect this diagram is being utilized for illustrative purposes only. It is with merit to note that the hypothesis indicated and the data demonstrated a trend toward a forced bend at point A: the forced bend was also accompanied by a decrease in COM velocity. In reflection, maybe it is a visual interpretation of their hypothesis: plant the pole flat footed, and force the bend through a press with the arm through the take off. Nonetheless, under the experimental definitions early, middle and late plants/takeoffs are indicated somewhat by the vaulter at points A,B, and C respectively: just not necessarily with the accompanying pole bend.

0001l3.jpeg (21.85 KiB) Viewed 16957 times

The next diagram is included for illustrative purposes only: the author stated that the ground reactive forces in this chart were not an indication of the total information collected. The vaulter diagram at the top of the chart shows the vaulter progression through the Jagodin; note there is no swing velocity.

pole plant ground reactive data.jpg (38.89 KiB) Viewed 16957 times

The next diagram is a brief and partial description of the equations utilized which I am certain have some merit and I did not delve into in order to avoid the ensuing headache that would follow. The basic premise is that total energy transfer was calculated based on a multitude of measurements: one of the measurements was the distance of the pole chord. My concern was that an inappropriately large value/weight was placed on the shortening of the pole chord. The basis for my questioning lies in the researchers own data and subsequent conclusion which is noted below.

"As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality."

0003Tx.jpeg (41.9 KiB) Viewed 16957 times

The research noted a degrade of COM velocity when the pole bend was initiated "Early" while the vaulter was still on the ground in a position close to vaulter A in the first diagram. However, in the calculation of energy transfer and in the concluding remarks this fact was minimized because of the numerical value/weight placed on the short chord of the pole represented by a large pole bend. I have include the researchers concluding remarks below.

"We found neither statistical significant differences in the mechanical energy level of the vaulter/pole system during take-off between the three groups nor a relationship between the timing of the pole plant and the energy level of the vaulter–pole system during take-off. We conclude that although the timing of the pole plant
influences the interactions between the vaulter, the pole, and the ground, it does not affect the athlete’s
performance. Although a late pole plant decreases the loss of energy by the vaulter during the take-off,
this is counterbalanced by a decrease in the energy stored in the pole at take-off"

The last point is entirely important yet the researchers are trying to minimze the implications of it:

"Although a late pole plant decreases the loss of energy by the vaulter during the take-off,
this is counterbalanced by a decrease in the energy stored in the pole at take-off"

So, if you are transferring energy into the system more efficiently, as indicated by the vaulters COM velocity increased as a result of a takeoff closer to that of Petrov in comparison to a pole plant at heelstrike with a bigger bend and a lower COM velocity, then the advantages of the higher velocity takeoff are just counterbalanced? I entirely disagree...

So, basically the researchers are trying to state that the "athletes performance" is not affected by a decrease of velocity into the vault/pole system as long as you get a nice big bend while your still flat on the ground. I will post the data charted by the researchers which supports the statements that I have made in this and prior posts and indicates a bias, whether intended or not, towards an unreasonably high value placed on pole bend even when the vaulters COM velocity is degraded as a result.

"Any intelligent fool can make things bigger and more complex... It takes a touch of genius --- and a lot of courage to move in the opposite direction."

V

[coachjvinson]

What the study does appear to state is that an early plant - planting close to or at a point near the heel strike - will bend the pole more at the expense of the vaulters energy as quantified in this experimental design.

We hypothesize that an earlier pole plant during the stance phase of the jump will increase the pole energy at takeoff compared to the energy decrease of the vaulter and so lead to a higher energy level of the vaulter/pole system at take-off."

Their hypothesis under the experimental definition was that an early pole plant close to the moment of heel strike would load or bend the pole AND result in a higher level of energy of the vaulter/pole system at take-off.

The data below shows the energy stored/transferred into the pole as quantified in the equation and the definitions of the experimental design. pole energy is charted on the Y axis and take off/pole plant (T-PP) is charted on the X axis as a function of time after heel strike. The data points further to the right indicate a take off/pole plant (T-PP) action closer to the model of Petrov as indicated in the (T-PP) action being further away from the Zero point measured by the heel strike moment and closer to the plantar flexion action of the Petrovian Takeoff. Further, the data points indicate a lower storage/bend/transfer of energy into the pole when the (T-PP) is nearer to the point of the Petrovian Takeoff. These data points and figures were criticized due to the experimental design and definitions placing a classification of a lack of energy storage/bend/transfer into the pole: even though the vaulter's COM velocity is increased at the points which are closer to the Petrovian Model.

pole plant data 1.jpg (21.48 KiB) Viewed 16951 times

"Therefore our hypothesis is rejected. The findings indicate that an earlier pole plant (close to the point of heel strike) is related to an increase in pole energy as a function of the energy exchange between vaulter and pole, rather than the result of additional energy production."

Their hypothesis was disproved and their findings indicated that a pole plant near the point of heel strike did in fact load and bend the pole more; However, the overall transfer of energy into the vaulter pole system was decreased and compromised.

The data below establishes that as the the (T-PP) approaches the Petrovian end of the spectrum that the Vaulters Energy transfer increase, there is a direct correlation between a near Petrovian (T-PP) and the Vaulters Energy/COM velocity into the vault/pole system....
This fact alone is beyond substantial...

pole plant data 2.jpg (26.66 KiB) Viewed 16951 times

The next chart shows a similarly direct correlation between a near Petrovian (T-PP) and the forces measured in the plant box; this appears to represent that a (T-PP) nearer the Petrovian model (T-PP) maintains greater pressure on the pole during the swing phase of the vault.

pole plant data 3.jpg (23.45 KiB) Viewed 16951 times

Okay, so I have reached my three attachment limit: in the following post, I will include the data chart which is the representative of total energy transferred into the vaulter/pole system as defined within the calculations and constraints of this particular experimental design.

In fact, the more I look at the data, the more this experiment appears to support the Petrov model - looking at the charts of the data provided, their is a direct correlation between the timing of the pole plant with energy into the system: as the pole plant timing is closer to the take off (late in relation to the heel strike and closer to the point of plantar flexion) there is a trend of greater energy transference not only independently among the same vaulter but within the group as a whole. Further, there is an indirect correlation between the load or bend of the pole and the take off time: the closer the pole plant to the point of takeoff, the less of a forced load or bend is placed on the pole.

"Imagination is more important than knowledge."

-V

[coachjvinson]

"I am neither especially clever nor especially gifted. I am only very, very curious."

"The findings indicate that an earlier pole plant is related to an increase in pole energy
as a function of the energy exchange between vaulter and pole,
rather than the result of additional energy production... "

"An earlier pole plant increases the energy transfer to the pole,
but causes simultaneously a similar decrease in the vaulter’s
energy."

so here is the basic overal vaulter pole system energy diagram...

pole vault energy calculation diagram.jpg (52.9 KiB) Viewed 16928 times

and here are the points plotted which represent transfer/change in the mechanical energy of the vaulter/pole system during jump and plant complex: Energy Quantified on the Y axis and Takeoff Pole Plant (T-PP) on X axis

pole plant energy transfer data.jpg (35.9 KiB) Viewed 16928 times

Basically, as stated previously the vaulter has a greater total energy into the vault system as the vaulter approaches the Petrovian Model, and we can safely infer that this will amount to a greater rotational pole speed from takeoff pole plant (T-PP) to vertical even though it appears that neither this nor vaulter swing speed is included in the overall vaulter pole system energy transfer. Additionally, as the vaulter approaches the Petrovian Model, the vaulter appears to have an overall greater pressure on the pole as well as a functional bend in the pole which is more a function of runway and take off COM velocities than the hypothetical creation of stored energy into the pole through the use of muscular force at the takeoff pole plant (T-PP): a hypothetical idea which was disproved in this experiment.

Yet, somewhere in the measurements and calculations the results are skewed towards a conclusion and determination that even though their are noted gains in energy transference into the vaulter pole system, especially the holy grail of vaulter COM velocities, the gains appear minimized in the calculations and data collections presumably based upon on an inapplicably excessive weight and value of pole bend.

Although a late pole plant decreases the loss of energy by the vaulter during the take-off, this is counterbalanced by a decrease in the energy stored in the pole at take-off.

Remembering of course that under the experimental design and experimental definitions a later pole plant is that which approaches the take off pole plant (T-PP) of the Petrovian Model.

It should be noted that none of the subjects executed a pole plant close to the take-off. Our findings reveal valid mechanisms of interaction between vaulter and vaulting pole, therefore we do not believe that pole plants close to take-off would have influenced our findings fundamentally. A free pole plant, which is a plant that occurs after take-off, was not executed either.

In conclusion, even though it was generally observed that the vaulters did not execute a free take off nor a plant close to take off, the closer the measured group of vaulters were to the Petrovian end of the spectrum, there exists an observable gain in efficiency of COM velocity transference, an observable and inferable tendency away from energy transference degradation through pole bend/load, and an observably higher maintenance of force and pressure on the pole in the box. This experiment demonstrates the need for a more thorough analysis of the vault and the experimental designs utilized toward this goal.

"I don't believe in mathematics."

I would like to take the time to look closer at the overall energy transfer calculations, as it stands my observations are based on the data analysis collected and graphed in the research.

"Everything should be as simple as possible, but not simpler."

-V

[ADTF Academy]

The first major piece of the puzzle I would want to know before taking the research too far is the following.


Position of COM in relationship to foot at TD and at PP. That would dramatically change the perception of some of the results.


If Vaulter F though PP was early in stance, but if his COM was beyond TD strike (towards box) than in relative terms his takeoff looks different on paper.


If Vault A reaches and his TD is in front of his COM than the time reported could simply be partly the time for his COM to move over his foot as well as PP.

Either way for me without knowing the position of the COM at PP impact in relationship to the TD foot I think its hard to really sum up anything but COOL DATA!!!!! No practical use is available.

The fastest athlete loaded the most energy.... We already knew this. I wish they would have taken it more steps. What was the velocity at 2nd to last step. Angle coming off that step. Relationship of TD foot to COM and Relationship of COM to TD foot at pole plant.

Maybe the vaulter who has PP at 12 frames had excellent Jumping ability and got his foot under his COM before TD therefore he was actually past his foot slightly at PP. Wouldn't this change the vantage point of the entire data? Just because it was an early strike in relationship between TD and PP doesn't show the whole story. Where is COM in relationship to all the data collected is my #1 question.


(I've sent an email off to Germany to try to get in touch with the Researchers to get this information. I will keep you posted if I get anything back)

[agapit]

It’s quite astonishing how sometime if one does not ask the right question then the right answer to the wrong question is still wrong answer. Let me elaborate.

In one of my writs, I have hypothesized that actually from the pure preservation of energy at the takeoff it may be advantageous to not to jump of the ground at all, however paradoxical it may sound, and the plant timing, pole/ground angle or being under, or having a free takeoff has no significant influence on total energy of the athlete/pole system at the takeoff on the fiberglass pole or at least not as much influence as on the rigid pole.

I even would argue that larger takeoff angle generated by an athlete could be costly from the energy perspective, because resistance of the takeoff leg required to generate larger takeoff angle consumes energy in the muscle/skeletal apparatus of the athlete and I hypothesized that the pole can “lift” the athlete off the ground with a greater efficiency, loosing less energy in the process, because the fiberglass is more efficient then the human muscle/skeletal system in redirecting speed vector up.

So, if I would look purely from energy exchange perspective during the takeoff phase and that is all we were interested in, I could argue with anyone, that in fact a flatter takeoff would be more energy preserving and timing of the pole interaction with the athlete would have no difference on the total energy in the system!!! So I would find the conclusion of the experiment in question not unexpected. Moreover, pillars of pole vault coaching such as Don Hood, advocated for a flatter takeoff and Billy Olson’s WR was an outcome of this method!!!

However, it is not just preservation of energy that is at stake at the takeoff, no pun intended! The potential height of the jump depends on the total energy generated and preserved during the whole event not just run-up/takeoff. And if one considers the whole jump then timing of the plant and takeoff as well as the direction of the takeoff significantly influence ability of the athlete to further generate energy input in the system. See my discussion about passive and active phases. Also the most important parameter in the achieving higher clearance is the vertical speed component of the center of gravity or COM and having the most streamlined COM trajectory without significant decelerations/accelerations is essential! And however great Billy Olson’s achievement and potential was, we estimate that Bubka’s was about a foot higher!!!

[altius]

Love the Einstein quotes Coachjv. I have already detailed my take on the biomechanics of the vault in BTB2 - not going to start again here. However I have never been sure about the opinions of the bio mechanists - in this case I prefer the views of a guy - Sergei Bubka - who trusted his life to a technical model which he thoroughly understood and believed in.

I also think it is worth noting that while bio mechanists have usually managed to explain (retrospectively) why things work in track and field, they have never developed new and effective solutions to the problems athletes face as they strive for excellence. The OBrien Shift and the spin technique in the shot put as well as the development of the 'flop' technique by Fosbury come to mind.

[dj]

Difficult to really "follow" who is saying what in studies such as this… like Roman said you ask the "wrong, right" question and you will always get the wrong right answer.

Ie.. stiffness of the pole has more to do with the takeoff angel than anything the vaulter can do at the takeoff, like jump up..

In the 70's the best vault coaches were "coaching" the vaulter to "run of the ground, with the pole as high as possible, directly toward the back of the pit. jump "over" the pit with the plant high and the horizontal velocity will more readily be transferred to vertical height.

The ONLY vault technical "issue', really, that can't have a IF or AND, that will "predict" a marked result, is the vaulters horizontal velocity and correct transfer ( as per Alan/Bubka and a few others) of that velocity, with the right grip and pole into vertical height.

RUN… PLANT.. SWING

dj