Each pole has what we call a load factor, this is the maximum load the pole can survive. This number can also be misunderstood if one does not understand the mechanics of the pole vault. A load factor can measure the whole pole, but is totally determined on the pattern make up and design. The best energy saver and energy return is a pole that is smooth and timed to the vaulter. This is done by years of experience in pole vaulting and pole making to know what balance of Sail design and placement to body wrap and Hoop wrap is required.
The best pole in the World is the one that fits you, one you can capture the timing and the ride to maximize the return. If the pole is dominate body wrap it will be too fast for today's young vaulters. If too much hoop the pole will bend but not provide the degree of return strength to lift the hips. The importance of pole design is crucial to know how the vault transpires, as well as how to blend the pole resistance to give a smooth transition from pole to pole from length to length!
This sail of the pole is important as it reinforces the load of the most concentrated portion of energy into the pole while it bends. And this controls the stiffness along with other factors; mandrel size, body wrap sizes, and wrap lengths.
It is important to have a balance of sail, body wrap, and Hoop wrap in a pole for the maximum smoothness of the ride! As the pole increases in stiffness one may shift towards a more dominate Body Wrap to increase return. It is important to not build the line with this concept fully or you will have a pole that returns faster than a vaulter can manage.
The pole grip is calculated by the distance of the top of the upper hand to the end of the pole at the butt. This factor determines the leverage point at which energy is stored to the pole. This factor is variable and maybe adjusted from jump to jump by 2" to 6". Moving a pole grip up by one to two inches from established grip will provide less resistance and the pole will bend easier. Just as lowering a pole grip, reduces the load point making the pole feel slightly stiffer to bend and will return faster in recoil. There is a point when the energy input is lower than the sail design and the load which feels to be stiffer is not necessary the load capacity of the pole at that concentrated point. The Pole bends low and does not perform or bend properly.
An erroneous assumption of some vaulters and coaches is that the more you bend the pole, the better the results. On the contrary, over bending the pole beyond 105 degrees provides no advantage in reflex action. It does cause a slight interruption in the smoothness of the vault, hindering timing. there are so many differences in vaulting techniques as well as variables that come into play, no set formula can be precisely determine the idea model. As you develop your technique, a vaulter finds a greater push off potential and more personal records from stiffer shorter poles, working on technique. The goal should be a 12" to 24" push off.
(Side Note: Currently both Timur Morgunov Russia and Sam Kendricks USA are pushing a 4 foot + clearance over a bar at 6 meters.)
Properly made Poles should not be so hard to bend, and a wide hand-spread will bend the pole, however the bottom arm if not in the proper position can kill the swing-up and stop you from catching the ride. The optimum situation is to reduce the hand-spread to rotate faster and time with the pole for the very best energy reflex action! If you are over gripping you cannot manage the recoil of the pole and poles today will return without you in the sweet spot position. Warming up with a stiff pole and short grip swing-ups and riding the pole into the pit is a good way to enhance the swing-up. Steve Smith 1972 Olympian use to jump with a metal pole to build his swinging technique. Starting beginners out on stiff pole is a good way to develop on going skills.