Imagine running at full speed carrying a 15 foot long pole. You approach a large foam mat and a high bar spanning across two rigid standards. Once you are a few feet away from the mat, you lower the front tip of the pole into a hole in the ground, raise your arms up towards the sky, and jump as high as you can. In less than a second, the pole bends and you swing your legs up above your head so that you are completely upside-down. Your body is launched upwards, and once the pole fully recoils, you let go and suddenly find yourself floating 17 feet above the ground. Just as quickly, you plummet back towards the earth and come to rest comfortably in the middle of the foam mat (for illustration, see Fig. 1)
A Brief History
The Process of Pole Vaulting
The approach allows the athlete to build up speed and prepare for the plant and take-off. The vaulter starts from a standing position, places his hands spaced apart at one end of the pole, holds the pole in a vertical position, and then slowly lowers the tip of the pole as he approaches the box and pit. During the plant/take-off, the vaulter lowers the pole tip into the back of the box, raises his arms up above his head (with the left hand about a foot farther forward on the pole for a right-handed person), and jumps up off the ground while still maintaining his forward momentum. These actions result in the pole bending and gaining energy, which will later be used to propel the vaulter upwards (Fig. 2). During the swing-up, the vaulter swings his legs up over his head towards his hands, bringing his body upside-down and in line with the pole. Once upside-down, he “pulls” the pole against his body and past his head, performing a handstand on top of the pole. This then leads to the final step, the push-off, in which the vaulter throws himself off his pole and curls himself over the bar, while at the same time rotating his body so his stomach is facing towards the ground. These movements allow the vaulter’s body to contort over the bar with more ease. Finally, the vaulter falls back to the pit and comes to rest on his back .
The Physics Behind the Vault
Through the transfer of energy, a vaulter is able to launch himself up to 20 feet in the air, depending on his speed and weight. The greater the vaulter’s speed and mass, the more momentum he can build up during his approach, and thus the more energy he can transfer into the pole. Using a man with a center of mass 1.0 meter off of the ground who can run with a speed of 10 meters per second as an example (values for an elite athlete), the formula predicts that he should be able to vault about 6.10 meters high . This result is surprisingly accurate, considering that the world record is currently set at 6.14 meters, a mark achieved by Sergey Bubka of Ukraine in the early 1990s. The slight differences between the theoretical and actual heights have to do with the pole’s efficiency in transferring energy, which will be discussed later.
The Evolution of the Vault
A Shift in Focus from Athlete to Pole
Evolution of Pole Materials
Hardwood (Ash or Hickory)
When pole vaulting competitions began in the mid-19th century, the poles that were used were made of heavy, rigid hardwood such as ash or hickory. The athlete would climb the pole after he planted and jumped, and throughout the vault, the pole remained rigid and had essentially no bend. The basic technique of the hardwood pole vault can be seen in Fig. 5. In 1889, American vaulters banned the pole-climbing technique and implemented the swing-up technique, an early version of the modern method , which added height to the vault . Despite the advancement in technique, however, the hardwood poles were limited because they could not bend. As a result, the poles could not transfer horizontal motion into upward motion efficiently, as a large amount of energy was lost in the plant and vaulters were constrained to lower heights.
Around the same time that the swing-up method was introduced as the definitive technique in the vault, bamboo poles began to replace the hardwood ones. The swing-up necessitated a new type of pole that had some bend, and bamboo fulfilled that need. Also, the box was introduced into the plant stage (previously vaulters had simply stuck the pole in the ground), which required the pole to have some bend as well. The swing-up technique can be seen in Fig. 6, where a vaulter uses one of these new poles to clear a height. Bamboo poles were much lighter than the solid ash or hickory poles due to the fact that bamboo is naturally hollow, which allowed for a faster approach. Additionally, these poles had a lesser degree of stiffness and thus had a minor ability to bend when stressed. For these reasons, vaulters were able to carry more energy into the vault and convert more energy into an upward motion.
Fiberglass and Carbon Fiber
While steel and aluminum poles made a brief appearance in the world of pole vaulting in the 1950s and 60s, the next major advancement in pole technology came in the form of fiber-glass and carbon-fiber poles. A cross section of the design of these poles can be seen in Fig. 7, which shows the different layers that allow the fiberglass pole to be so versatile and effective. The poles were first introduced in the U.S. in 1956, and immediately made an impact on achievable heights, evidenced by the new world record set in 1961 at 4.83 meters .
The Future of Pole Vaulting
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