Tim, I get what you're saying, and if that's what Agapit is saying, then I get that too.
What you've just described is an excellent model for a straight-pole vaulter to use. But does it apply to bent-pole vaulting?
There's 2 key differences in bent-pole vaulting that I don't get yet (in relation to this 640 Model).
1. The chord of the pole is much shorter than the grip. That's why bent-pole vaulters can grip so much higher than straight-pole vaulters.
2. The pole (bent-pole or straight-pole) must rotate to vertical in order for the vaulter to extend efficiently off the top. The ability to rotate to vertical is dependent on the grip (for straight-pole) or the chord (bent-pole). So in bent-pole vaulting, getting an optimal bend is important.
Considering these 2 key differences, I'm still not seeing how it's optimal to pull with the bottom arm immediately after the pre-stretch.
It seems to me that if you pull this early (and if you're REALLY strong - in the extreme case), you'll pull yourself into a back uprise ... which is totally going to screw you up on the pole ... you'll slow the pole's rotation, and you'll stall out.
Furthermore, if you pull this early, then it seems to me that you're NOT going to have that long, low trail leg swing that's going to add energy into the pole ... energy that will accelerate the whip ... but will also aid significantly in keeping the COM low enough so that the pole can rotate faster.
It is possible that we're all talking about the same thing here, but words may be getting in the way of what we perceive as "
optimal technique".
Tim, let's continue using your highbar analogy is an excellent reference point ... for straight-pole vaulting. But let's now think about a theoretical highbar that has the bend of a fiberglass pole - bending a meter or more (shortening the distance between the 2 uprights by a meter or more). For the moment, forget about the bottom arm and bent lead knee ... just think about a symetric 2-handed hang and 2-legged swing in this analogy.
Now think about when the trail leg (both legs on the highbar) and the pole (highbar) must aid in the whip, in relation to the pull of the bottom arm and the pull of the top arm (both arms on the highbar). Is it not AT THE CHORD ... THE WHIP?
It seems to me that all 4 of these "
things" (top arm, bottom arm, trail leg, pole action) must come together somewhat simultaneously, at approximately the instant in time just before the trail leg passes the chord ... on the highbar and on the pole. This point in time (and this action) is also known as the "
whip".
From being straight on takeoff, the pole bends to the chord. This takes a finite amount of time. A split second, admittedly, but still a certain amount of time. Sufficient time for the vaulter to finish his takeoff (to and thru the pre-stretch), and then enough time to start ... AND FINISH ... the downswing. These are sequenatial actions ... easily separable, and easily performed one after the other (with sufficient talent and practice).
During the downswing, the vaulter is not only swinging his trail leg down and forward, he's also transforming his body from a "C" to an upright "I" ... the "I" being when he passes the chord. It is at the chord that I think the top arm and trail leg should have already reached their max acceleration. This max acceleration is "
the whip".
I agree 100% that during this WHIP, the bottom arm must pull ... exactly as per a highbar giant, and exactly as described by you, Tim. And in my mind, the bottom arm should optimally pull JUST BEFORE THE CHORD. The culmination of the top arm and trail leg is what produces the whip ... and the bottom arm pull (timed "
properly") accelerates it even more. In turn, the whip produces the maximum bend (aka the chord).
What I don't get is how (in the 640 Model) the bottom arm needs to lead the top arm and trail leg in this quest. Why is that better than the top arm and trail leg initiating the whip, and the bottom arm THEN accelerating it?
I guess it comes down to each person's definition of when exactly we think the pre-stretch is finished, and when the top arm (let alone the bottom arm) should begin to pull. If we could at least see eye-to-eye on that, then maybe the timing of the bottom arm pull would become more apparent.
Funny, but I'm thinking right now that the only difference here might be in that split second when we're drawing our trail leg back to an extreme C. You did that in your Drive Model (aka Dial Model) and I did that in my Bryde Bend. If that split second of time is eliminated (eliminating the extreme C ... which I would not do, as it' allows the chest penetration needed for the pole to rotate optimally even with a high grip), then the pull of the top arm (roughly in unison with the trail leg) is the same in all models!
Tim, I'm sure that you understand what I'm trying to say ... whether you agree with it or not. I know that you have the personal experience with the extreme C to understand my viewpoint. Could you possibly put this in your eloquent English, as per your last post?
And clarify anything that I still don't "
get"?
I believe that we're both trying to understand the 640 Model and its merits according to the Laws of Physics ... in relation to our own personal experience with our own "
models". And I think it's possible to understand different models without agreeing with them. I'm trying ... but I don't think I'm quite there yet. You may be closer than me.
Kirk