Pole vault: Fosbury Flop flips jumping game

Every now and then in sport, a person comes along who changes everything.
Whether by calculation, intuition, or luck, such athletes tap into an aspect of their sport that had been previously unknown but, once revealed, seem disarmingly obvious.

Perhaps the most famous of these savants is Dick Fosbury, the American high jumper who set alight the 1968 Mexico Olympics with his gold-medal winning backward flip. His 2.24m jump, which also set a new Olympic record, immediately became known as the 'Fosbury Flop', and is now a near-universal technique employed by modern-day jumpers.

Until that point, high jumpers had either used the scissor-kick method, which is still in currency at most primary school sports days around the country, or the straddle method, an ungainly front-on approach where jumpers hurl themselves at the bar and try to straddle over it.

One of the catalysts for Fosbury's backward technique was the introduction of foam padding to cushion jumpers' falls.

Until that point, mounds of sawdust were used, as the scissor- kick and straddle didn't involve jumpers landing on their backs.

Fosbury's technique may have looked radical at the time, but it had the benefit of squaring nicely with some fundamental scientific principles.

John Barrow, a mathematician at Cambridge University, explains that the genius of the Fosbury Flop is that the jumper's centre of gravity, or centre of mass, stays low to the ground, which means that less energy is needed to clear the bar.

The centre of mass of an object is defined as the "average location of all the mass in an object".

What makes the Fosbury Flop revolutionary is that it enables a jumper's centre of gravity to travel underneath the bar while the jumper clears the bar.

Barrow points out that if an object has a bendy or irregular shape, the centre of gravity for that object can be positioned outside of itself.

Because a high jumper leaps into a semi-circular position at the top of his flight, with his back facing the ground, the centre of mass will be positioned somewhere between the jumper's feet and head. That is, lower than the athlete's back as it crosses over
the bar for a successful jump.

To achieve this, a high jumper has to launch with as much vertical speed as possible.

Dr Jesus Dapena, a biomechanicist at the University of Indiana, estimates the point of take-off for a high jumper lasts between 0.16 and 0.20 seconds.

In that time, the athlete must make a substantial "vertical impulse" on the ground.

That requires jumpers to swing their arms and front legs hard to create the maximum amount of upward forces.

The high jump world record was achieved using the Fosbury Flop. In 1993, Cuba's Javier Sotomayer jumped a staggering 2.45m in Salamanca.

That record is 10cm higher than the best straddle-technique jump, which was achieved by Ukraine's Vladimir Yashchenko in 1978.