The topic of this post is “
Scalability” …
Before I compare my short run vault to my long run (competition) vault, I’d like to define the word “scalable”, or “scalability”.
In computing, this term refers to how well a hardware or software system can adapt to increased demands.
For example, a single web server might have a certain number of users that can access it simultaneously. But when you double the number of users, each user’s response time might become intolerably slow. i.e. much more than twice as slow. That’s an example of a computer system that’s not very scalable. But if the response time remained constant, independent of the user load, then that’s an example of a scalable system.
Another real world example – outside the realm of computers – is electric cars. Toy remote control cars run on electric batteries, and are really, really fast for their size! And they can run for hours! (Or at least quite a long time between battery charges.) But increase the size of the toy car to one that would fit a human in the driver’s seat, and the battery is way too big, it runs out of juice way too soon, and doesn’t run very fast at all - comparably.
In the car example, electric batteries aren’t very scalable. You can’t just increase the size of the car and the size and weight of the battery and expect the car to be proportionally “as effective”.
That’s what I mean by being “scalable”.
In pole vaulting, the athlete + the pole is also a “system” that can be scaled. Like the computing example or the electric car example, PV has various metrics that you can scale. For a given technique, there’s your takeoff speed, your weight, your height, your grip, your strength, and your pole flex. Adjusting any of these will affect how high you can raise your CoG over the bar.
Unless you take growth hormones, you can’t do much about increasing your height – other than reaching and/or jumping off your takeoff a little higher. And you can change your strength or weight, but not overnight.
Your speed on takeoff is somewhat proportional to the length of your run, so you can say that the length of your run is also an important metric. In fact, that’s one of the metrics that I’ll be focusing on. But I won’t break the run down into stride length, cadence, and the Mid Mark Chart. I won’t go there! That’s a different thread!
The premise of biomechanics like Peter McGinnis and Nicholas Linthorne for decades has been “the faster your run, the higher your bar clearance”. And so (assuming constant acceleration), run speed is proportional to run length, so just increase the length of your run, and you’ll jump higher, right? Wrong.
The assumption of constant acceleration is wrong. There’s laws of diminishing returns at work, and your run should be no longer than what’s required to reach full speed (and they maybe add a couple more steps to get that max speed under control).
In other words, your run scales your vault only within certain minimums and maximums. The minimum length run [needed to reach an “effective” vaulting speed] defines your short run vault, and the maximum [needed to reach full speed] defines your long run (competition) vault. Let's not quibble about doing other types of short run vaults of various lengths - like 2 lefts or 3 lefts - for various specific, isolated purposes. For now, I'm only talking about your "best" short run vault, where you "put it all together".
In order for your vault to be SCALABLE between your short run and your long run, your run length should be PROPORTIONAL to the other metrics that you can easily vary – such as pole flex and grip.
The challenge is to make your short run vault SCALABLE to your long run vault – and vice versa.
Clearly, there’s some mathematical relationship between your takeoff speed, your grip, and your pole flex that might give you a hint as to optimizing the height of your CoG over the bar. But what is it?
It’s not a linear formula, it’s a non-linear formula – a curve. McGinnis plotted the velocity (in the last 2 steps before takeoff) of elite vaulters to their PRs. (See: Biomechanics on a Budget
http://www.pvei.com/fusion/readarticle.php?article_id=23). But in real-life, it’s not that simple. Velocity on takeoff isn’t all that matters. (To be fair, McGinnis has written many other articles where he recognizes this over-simplification.)
Linthorne (See:
http://people.brunel.ac.uk/~spstnpl/Publications/PoleVault(Linthorne).pdf) plotted height, grip, pole flex, takeoff angle, and takeoff speed to PRs. He was close, but still no cigar. It’s still not quite that simple. There’s more factors than these!
With 100% optimal technique (something that not a single elite vaulter has attained yet), you can OPTIMIZE the addition of more energy into the pole AFTER TAKEOFF to go higher. (Like McGinnis, Linthorne was aware of this too. It just added too much complexity to his formula, so he arbitrarily added a flat 80 cm to each vaulter’s theoretically optimal vault – just to align the outcome of his formulae with real-world PRs.
To be fair, he identified this constraint in his paper. On page 210 ...
… To account for this shortcoming, 80 cm was added to the calculated vault height of each jump”.
Like the scalability of an electric car, there’s certain caveats that you need to be aware of in scaling your short run to your long run vault – which I’ll elaborate on in a subsequent post.
This isn't a happy story, where I did it all perfectly and advise you to follow the same path. Rather, it's a realization and admission of an important aspect of my training where I might have done better - knowing what I know today.
To repeat, the challenge is to make your short run vault SCALABLE to your long run vault – and vice versa.
The missing metric here is “technique”. Optimal technique has minimal leakage. Sub-optimal technique doesn't. Besides stopping leaks, optimal technique ADDS to the energy of the system. Sub-optimal technique doesn’t (as much).
Does this all make sense to you, so far?
Kirk
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