Getting into pole position

Eliza McCartney of Auckland. Photo / Getty Images
Eliza McCartney of Auckland. Photo / Getty Images

Most sports seem meaningless when cut back to base level but many served a purpose back in the day. In pole vaulting, for instance, the sport evolved in Europe from people trying to cross from one side of a canal to the other.

In the late 1800s, competitions popped up, and in 1896, it was included in the first modern Olympics in Athens. Vaulters originally used bamboo sticks with sharp points which dug into the grass (there were no holes, or vault boxes back then) and, once they'd vaulted over the bar, landed back on the grass.

The winner at the first Olympics achieved a height of about 3.2m - today's world record is 6.16m, set by Frenchman Renaud Lavillenie in 2014. There's a fair bit of science behind pole vaulting in both the technique and materials used.

In terms of equipment, the poles have evolved tremendously. Metal poles, which were lighter and stronger than bamboo, became popular after World War II (by this stage, the world record was about 4.7m) and these were eventually replaced by fibreglass.
Today, athletes use a pole made from carbon fibre and fibreglass composite which wastes very little energy when it bends and offers a good strength-to-weight ratio.
The height and weight of the athlete makes a difference and poles vary accordingly.

A heavier athlete needs a stiffer pole, but it still needs to bend as much as one used by a lighter athlete. The weight of the pole has decreased over time - although they are much stronger - and this has allowed athletes to run faster, a crucial element for a successful vaulter.

This is where physics come in so, even if you flunked NCEA physics, hang in there. It's all about kinetic energy (KE) and potential energy (PE).

The speed of the athlete running down the runway is kinetic energy - the faster the athlete, the more kinetic energy and the higher they should be able to vault. Once the pole is planted, it bends, absorbs the kinetic energy and transfers it into potential energy in the pole.

The athlete uses the potential energy in the pole to lift themselves upwards towards the bar, a bit like a spring uncoiling. Once they approach the bar, they should have just enough kinetic energy to clear the bar and drop down to the mat.
Contrary to what many believe, vaulters don't use strength to lift themselves over the bar. Instead, it's about running as fast as possible without compromising technique (speed accounts for two-thirds of the height that can be gained) and then using the energy in the pole.

Interestingly, male vaulters are at about the limit of what they can achieve unless pole technology advances significantly or athletes can somehow run faster. In fact, Lavillenie's record is beyond what boffins thought was possible based solely on mathematics and it's part of the reason why it took 20 years for Sergey Bubka's record to be beaten - Bubka broke the record 17 times between 1984 (5.85m) and 1994 (6.14m).

Mathematicians believe the women's record, however, has the potential to advance significantly, given it is a relatively new event. Russia's Yelena Isinbayeva set the current record of 5.06m in 2009.

Eliza McCartney extended her New Zealand record to 4.80m last month and then placed fifth at the world indoor championships. She's an outside chance of a medal in Rio. The 19-year-old is one athlete who understands the science of what she does, considering she's studying for a Bachelor of Science in physiology.

"A lot of what I learn is relevant at training," she says. "It's like a practical after class."

- Herald on Sunday

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