It kind of goes against how you would regularly think about the vault, doesn't it? The more efficient a jumper you are in terms of your inversion ONLY, the lower you can grip (stiffer the pole can be) and the higher differential you can achieve. While the less efficient jumper you are, the higher you should grip (softer the pole will be) with a lower differential. So its interesting that it seems like the grip hieght you have on a pole is termined by your take off efficiency (more efficient= more grip) and the stiffness of the pole is determined by your inversion efficiency (the more efficient= the stiffer the pole can be). These are general guidelines for vaulters with near optimal grip hieght and optimal technical ability, and i wonder if you agree with this?
I may or may not discuss this in more detail. I'm still pondering on whether or not it would be beneficial. But I will give you this possibility to plug into the discussion. In 1985 the Dials were taking the idea of swing efficiency to its most extreme conclusion. The reason for this was because at 5'8" and under 140 pounds, he did not think we would ever be able to grip high enough to be competitive. Dean figured that the world record could be broken with a 15’ grip, and they were getting closer and closer working along these lines. In 1986 Joe decided he had to grip higher, and against Dean’s advice, he raised his grip to 15’10” and broke the American Record several times and the World Record once. I know I’ve repeated this too many times, but it bears directly on this question. Before he made the change, Joe jumped 18’10.5 with a 15’ grip. I saw it with my own eyes, and at that time Dean saw no reason at all to raise Joe’s grip much higher. He felt he could keep increasing pole speed indefinitely. The idea was to have the pole moving as fast as Joe could possibly time up with and just push off farther to jump higher. I inherited this legacy, and I feel that this is why I was able to compete despite my athletic limitations. It was no problem at all for me to grip 15’ and jump over 18’. But this is because Dean would not let me grip higher than 15’ until could jump that high. I once made 18’4” with a 14’10” grip in practice. (It was one of those magical days that I was never able to quite repeat.) My problem was that I wasn’t strong enough to time things up consistently. Anyway, everything about this approach to the vault is so counterintuitive and opposed to accepted theory that I am not sure it would even be wise to go into detail. The fact remains that it worked, though I seriously doubt anyone will ever take this particular road again.
Another key to the way this worked is pole design. The amount the pole bends and how the bend is shaped is crucial. Back in those days Cata-Pole gave you the option of an X, Y, or Z sail piece, with X being the highest and Z the lowest. Dean ordered a set of 17’ poles with X and-a-half sail pieces; in other words, as high as they would possibly build. He then cut the bottoms off of them an inch at a time as Joe tested them till they were 15’ 10” long. This meant that most of the strength of the pole was very low and it bent asymmetrically, like a fishhook. At that point they worked like magic. I had one of them in my series for years, and it was the first pole I cleared 18’ on, but I seriously doubt anyone else has used a pole designed anything like that. Dean also insisted that there was one exact right grip for a given pole design. We did not move our grips around once we found it. He used the illustration of a weight on a scale. Once you find the point of equilibrium, moving it even a fraction one way or the other tips the scale out of balance. I would sometimes raise my grip 2", but all of Joe's poles were taped in exactly the same place with a grip only as wide as his hand.
For anyone who might be tempted. DO NOT take a hack saw to your poles. Unless Dean Dial taught you how to pole vault and your pole is at least the equivalent of 40 pounds over your weight at 16'5" long it is not wise. We would have preferred not to cut our poles at all, but nobody would build them like we wanted. They thought we were insane. Dean once made me a pole at one of the major companies' facilities, but he had to sign a waiver and promise to never put their label on it. I never planted it, but he swore I could set a world record on it. The problem was that it was 60 pounds over my weight and 16'9 long. He wanted me to grip it at 15'4". I seriously regret never trying it. One of my vaulters used it in practice years later, and it worked just fine. Bruce Caldwell eventually made me a set to the specs I gave him back in '93 and those were the poles I took to the world championships. I could never jump higher than 17' on a standard 16'5" design.
Sorry for rambling. I am exhausted from grading papers all night. I always write more than I intend when I start.