Rugby: Nothing routine about kicking goals

Herald Graphic

Goal kickers in rugby are a superstitious breed.

As they contemplated the ball in front of them, Grant Fox used to shake his fingers, Andrew Mehrtens rubbed his eyelid, and Jonny Wilkinson would crouch and cup his hands in front of him as if praying for divine intervention.

It's a mysterious and delicate art in an otherwise brutal game. The mystery only deepens when one considers that forensic science, which has been applied to almost every other aspect of modern sport, has left place-kicking largely untouched.

Just how Dan Carter is able to routinely slot the pigskin between the posts is as baffling to the laboratories as it is to the bar rooms.

It's true scientists have studied aspects of the practice, but nowhere near to the extent that they've examined the drive shot in golf, for instance. What has been found is largely fragmentary but it is illuminating nonetheless.

Two researchers from Brunel University in the United Kingdom analysed the requirements for obtaining maximum distance in place kicks.

Distance is achieved through a combination of the ball's projection angle and velocity. They found that a projection angle of about 30 degrees was required to achieve the greatest velocity, and therefore the greatest distance. This is much lower than the 45-degree projection angle commonly used for other kicks such as punts.

The same study also showed the average backspin on a ball as it rotates end-over-end from a place kick is around four revolutions per second. The drag the ball experiences at this rate is minimal, and has almost no effect on distance.

A recent University of Auckland study investigated the placement of the supporting leg and foot on goal kicks. The researchers noted the planting leg acts as the axis of
rotation for the kicking leg.

They had supposed that the ideal planting foot position for the greatest velocity was around 30cm from the side of the ball.

However, this hypothesis proved wrong, with research showing there was no ideal position for the supporting foot.

The Auckland researchers also cited previous studies that showed velocity reduced up to 25 per cent when study participants were asked to aim their kicks at specific targets.
While the physics and bio-mechanics are incomplete, statis-tical analyses provide an intriguing picture.

One study by New Zealand scientist Ken Quarrie examined data from 582 tests between 2002 and 2011. Quarrie discovered that Wellington's Westpac Stadium was the worst place to kick at, with a paltry 67 per cent success rate. Loftus Versfeld in Pretoria and Millennium Stadium in Cardiff had the highest success rate at 77 per cent.

In the period of the study, there were 6769 shots at goal, with an overall success rate of 72 per cent. Quarrie also devised a formula to assess the relative importance of kicks, taking into account the scoreline and the time in the match at which the kick occurred.

Surprisingly, Carter didn't even get close to the top of the list, despite having an overall success rate of 77 per cent. The best was South Africa's Morne Steyn, but he was joined at the top by two unlikely characters - Australia's James O'Connor and Stirling Mortlock.

Who would have thought?