A most interesting blog (another one)

I am always googling around for athletics related blogs  and this time I struck gold. 
The blog 

Once upon a time in the vest

is one dedicated to the 50s and 60s. Reading the introductory paragraph of the blog
  

one encounters the sentence "you can relive your youth and the sacrifices you made for the sport". 

For baby-boomers like myself this is something I can relate 100 % to. 

For younger peole who are interested in the recent history of athletics I can only say that they will not regret the time spent in following that blog.

Pole vault: a sprinkle of physics

How high can an athlete jump with a pole? Let us make the simplest possible calculation and consider a vaulter approaching the pit at a speed of v. If his kinetic energy is converted into potential energy with 100 % efficiency we find that the jump height is 

Assuming a reasonable velocity of 10 m/s leads to a jump height of slightly over 5 m. But wait, this cannot be true. Today’s records exceed and by far the 5 m barrier. A look at the evolution of the world record over the years is quite instructive.

The 5 m barrier appeared realistic as long as the athletes were using a bamboo (or, later, steel) pole. But all this changed with the introduction of fiberglass poles. The world record stands now at over 6 m for men and even the women’s record exceeds 5 m. How is this possible. The standard answer is that the extra energy comes from the upper-body athlete’s muscles which bend the pole storing energy in it, energy which is later returned to the vaulter when the pole straightens. While there is some truth in this argument the situation is far more complicated. 

First, we must not neglect the fact that the centre of mass of the athlete is already elevated with respect to the soil by the order of a metre. Factoring this in would lift the barrier at 6 m in agreement with the current world record. 

But has anyone seen a 100 % efficiency necessary for the 5 (or 6) m jump? Linthorne discusses this matter in detail. According to his findings two important factors entrer into play. First, a flexible pole reduces the energy dissipated in the vaulter's body when the pole is planted into the takeoff box. Second, a flexible pole lowers the optimum takeoff angle, and so the athlete loses less energy in jumping off the ground. While a rigid pole would lead to an optimum takeoff angle of around 30°, for a flexible pole the optimum would be less than 20° and an approximate 25 % energy gain. 

Ekevad and Lundberg have made more detailed calculations trying to determine the optimal length and stiffness of the pole. In a first study they consider a passive vaulter (represented by a point mass at the top of the pole)

and find that an optimal pole length of 5.5 m (slightly longer that the 5.2 poles used by elite vaulters). The interesting result is that they obtain a 87 % efficiency in the conversion of kinetic energy to potential. However in another work of theirs they allow for  what they call ‘smart’ vaulters, meaning that they model the vaulter as a number of connected segments which can execute a given sequence of movements, and they find that the potential energy can attain 1.27 times the value of the initial kinetic energy of the athlete and the pole. This means that the contribution of the muscle work to the increase of the potential energy is quite significant. I would take this calculation with a grain of salt, since there exist neglected effects and simplifications which may modify the precise value. But if we may draw one conclusion from these calculations this is that we haven’t reached yet the limit of human capabilities in pole vaulting 

as the recent improvement upon a world record standing for 20 years has shown.

Pole vault: a women’s sport

Back in the days when women were not pole-vaulting (officially) I was dreaming of the day this missing discipline would be introduced, making it possible for women to compete in the decathlon. Alas, things did not go this way. Women have been participating in pole vault competitions for 20 years now but, as I am deploring in a previous article of mine, the feminine decathlon is a stillborn discipline.

When I started planning for a pole vault article I thought that, for women, there has never been a “before” and an “after”: the era of feminine pole vaulting started with fiberglass poles. This made me curious and I started researching: was it true that women never tried vaulting with, say, bamboo poles? It turned out that nothing was further from the truth. Indeed there were some serious indications that women did indeed vault. Even if this photo 

from the late 1800s were fake there is this magazine cover from the 20s

showing a young lady vaulting with a bamboo pole in perfect style.

Thanks to the contributors to the site PoleVaultPower.com I was able to find the women's world record progression. It is unofficial, of course, but who cares about such details. So the oldest recorded performance of a female pole vaulter was 1.72 m by R. Spencer in 1911. No details are known about the implement which could have been wood or bamboo. By 1935 the record was 2.53 m by Z. Romanova, most probably with a bamboo pole. In 1952 D. Bragg (the sister of Don Bragg who would later become an olympic champion) broke this record (one can surmise, with a metal pole) with 2.59 m. The first to jump over 3 m was J. Edwards who, from 1981 to 1983, took the record from 2.61 m to 3.59 m. By that time the fiberglass poles had dominated the pole vault scene. 

The first official world record was homologated in 1992. At that time several chinese athletes had improved the record from 3.72 m to 4.02 and the first official record, due to C. Zhang was 4.05 m. The supremacy of the chinese vaulters was soon to end and the world record became a european-american affair, with an australian interlude due to E. George. The first female vaulter over 5 m is the great Y. Isinbayeva who improved the record 17 times.

When I started following women’s pole vault I was not very happy with their style. I was not convinced by D. Bártová’s technique and I did not have the occasion to watch E. George (who has an excellent style) in action. Remember, YouTube was still years away. The first great, to my eyes, female pole vaulter, the one who jumped just like her male colleagues, was A. Balakhonova, European champion and record holder with 4.55 m.

Anzhela Balakhonova

But that was back just before the turn of the century. The new generation of female pole vaulters was arriving with S. Dragila, S. Feofanova and Y. Isinbayeva who, with their strength and grace, 

Liz Parnov in a most probably failed attempt (but I like the acrobatic style)

changed the face of this spectacular discipline making it a women’s sport.