Measuring and modelling the goalkeeper's diving envelope in a penalty kick

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Bibliographic Details
Title translated into German:Messung und Modellierung des Bereichs, der beim Elfmeterschiessen vom Torwart nicht erreicht wird (Diving Envelope)
Author:Kerwin, David G.; Bray, Ken
Published in:The engineering of sport 6. Volume 1: Developments for sports : Proceedings of the ISEA 2006 - Munich, Germany
Published:Wien: Springer (Verlag), 2006, S. 321-326, Lit.
Research institution:International Sports Engineering Association
Format: Publications (Database SPOLIT)
Publication Type: Compilation article
Media type: Print resource
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Identification number:PU200809003104


The penalty kick is a key set play in competitive soccer which often determines the outcome of a match, and when used in its 'shoot-out' format, resolves tied games during the knock-out stages of international tournaments. 85% of penalty kicks in open play, und 75% in penalty 'shoot-outs', result in a goal being scored. The purpose of this study was to establish the area of a soccer goal – the diving envelope - which could not be defended by a goalkeeper when facing a penalty kick. Video analysis of the 2004 European championship penalties revealed that the time between ball strike and arrival at the goal line ranged from 500-700 ms. Officially the goalkeeper cannot move towards the penalty taker until the ball has been struck and the area that he has to defend is 7.32 m x 2.44 m (24 ft x 8 ft) with the ball having to travel from a fixed spot, 10.97 m (12 yd) from the centre of the goal line. An electrically driven ball launcher (BOLA, Bristol, UK) was used to deliver two sets of 20 ball launches at two experienced goalkeepers in a simulated penalty shoot-out. The goalkeepers took up position on a force plate located at the centre of a soccer goal. All trials were simultaneously recorded using three digital video cameras within an indoor sports facility which had previously been calibrated to facilitate 3D DLT reconstruction of the video data. The launch velocity remained constant at 21 m•s-1 (47 mph) whilst the direction and height of each trajectory was varied to include left and right shots directed to low, mid und high levels. A goalkeeper model was developed based on jumping ability, derived from ground reaction force data, and anthropometry. Based on the ball flight time and the goalkeeper model a region of the goal was identified comprising 28% of the area which cannot be protected by a goalkeeper, meaning that players could guarantee scoring if they shoot into this 'unsaveable zone'. Observations from the two penalty shoot-outs at the 2004 European Championships revealed that many players do not take advantage of this zone and continue to gamble on the goalkeeper guessing incorrectly when taking a penalty. Verf.-Referat