Monday, 21 May 2012

The £47 Million Kick

It’s suggested that if you add up the prize money, enhanced media rights and the increased value of the squad, winning the Champions League benefits the club to the tune of £110 million. The losers benefit by £63 million – a difference of £47 million. For Chelsea in 2008 and 2012, this came down to a single kick. In 2008, John Terry had the chance to win the cup, but missed his penalty when his non-kicking foot slipped and his shot sliced wide. In 2012, the final would again be decided by the non-kicking foot. When you take a penalty with an instep shot, the direction of the non-kicking foot is a pretty reliable (80%) guide to the direction the shot is going (Franks & Harvey 1997). If it’s a side foot shot, you need to look at the angle of the hips (Williams & Burwitz 1993). David Luiz gave a demonstration of the perfect penalty. A fast run-up made it difficult for the goalkeeper to see which way the non-kicking foot was facing. The shot was hit with such power and placement into the top corner that the goalkeeper could never have saved it anyway. Didier Drogba had a short run up which would have made it easier to spot that his non-kicking foot was facing slightly left, so the ball would go to Manuel Neuer’s right. However, Neuer didn’t spot it, and dived the wrong way. Of course if you’re a Chelsea supporter watching the ball hit the back of the net, the answer to the question “Where was the German?” is “Frankly, who cares?” (B Davies 1988). David Donner

Tuesday, 8 May 2012

Olympic Countdown - Hockey

Penalty corners - Quite a lot of research has been done on the visual strategies of goalkeepers in football when trying to save a penalty. Very little such research has been done in field hockey (as opposed to ice hockey). If the defensive team commits a foul inside the shooting circle, the attacking side are awarded a penalty corner. All the defending players but five (including the goalkeeper) must stay behind the back line, while the other six have to stay behind the centre line. One attacker pushes the ball towards his team mates just outside the circle. One of them stops the ball and another one tries to score. If the ball is hit, it has to stay quite low to the ground, making it easier for the keeper to spread himself to save it. However, a flick is allowed to go higher, leading to the development of the “drag flick”. The drag-flicker gets the ball on the shaft of the stick and slings it towards the goal. One of the best known exponents of this art was England’s Calum Giles. So the goalkeeper has two possible strategies. One would be to focus initially on the pusher, and to follow the ball all the time. The other would be to keep their focus on the stopper and the drag-flicker at the edge of the circle. About a third of all goals are scored on penalty corners, so it would be really useful to know what the best strategy is. Canal-Bruland et al (2010) presented skilled hockey goalkeepers with video-clips that were captured either with a moving camera that followed the ball, or with a stationary camera that was directed towards the stopper and drag-flicker. The video clips were occluded 80ms after ball release from the flicker’s stick. Participants indicated where they thought the ball would go by pushing a joy-stick to one of the four corners as if they had to block the ball. They found that when they were presented with a moving picture that started with the pusher and ended with the drag-flicker, the goalkeepers were more likely to overshoot their gaze, beyond where the ball was stopped by the stopper. This tended to be associated with poorer decision making. Goalkeepers who spent more time fixating the ball and stick area, rather than following the ball, tended to make more successful decisions, whether the camera was fixed or moving. Also, goalkeepers who waited longer before initiating a movement tended to be more successful. What’s still not known is what information precisely the best goalkeepers are using. Is it something to do with the angle of the stick or simply the early movement of the ball? Research from football suggests that the direction may be picked up early on, but you need to be able to see the early path of the ball in order to judge the height. With advances in digital photography, it should be possible to highlight the relevant areas so you can work out the early cues that are being given. Then, all (!) you have to do is train your goalkeeper to recognise the cues, and your drag-flicker to disguise them. David Donner