Document Type

Thesis

Publication details

Alcock, AM 2010, 'Analysis of direct shots at goal from free kicks in elite women's football', PhD thesis, Southern Cross University, Lismore, NSW.

Copyright AM Alcock 2010

Abstract

In elite football, approximately one third of all goals originate from set plays, and of those direct free kicks are the most effective for scoring goals. The purpose of this study was to determine the key attributes of successful direct free kicks in elite women's football and the mechanisms involved in expert performance of the skill. A method was developed that could reliably locate a football on a pitch within 0.24 m using television coverage and the official pitch markings, and then applied to all direct shots at goal from free kicks in the 2007 women's World Cup. All seven shots that resulted in a goal were taken from within 27 m of the goal, entered the goal within approximately 1m of the goalpost, and had a significantly faster flight time than those that were unsuccessful. All shots directed towards the bottom and centre of the goal resulted in straightforward saves for the goalkeeper. This information can facilitate decisions on where direct shots from free kicks should be practised from in training and when a direct shot should or should not be attempted in competition. The attributes of a successful direct free kick were used to set up a replica laboratory-based free kick that would likely score in elite women's competition. Fifteen international female footballers performed simulated free kicks (curve kicks) and instep kicks at goal from the same location. Ball flight characteristics and full-body three-dimensional kinematics were analysed. Curve kicks had significantly greater lateral and vertical launch angles, increased sidespin and spin about the antero-posterior axis, and more spin about the vertical axis compared with instep kicks. Regression models demonstrated how carefully controlled the flight characteristics must be to hit the target with launch angles constrained to within 3°. To achieve the curved ball trajectory, players should take a wide approach angle to the ball, point the support foot to the right of the intended target, swing the kicking limb across the face of the target, and impact the ball with the foot moving upwards and in an abducted position. In both kick types, peak knee angular velocity and ankle linear velocity occurred at ball impact providing biomechanical evidence to support the common coaching recommendation of kicking through the ball. These findings could assist coaches by focusing their attention to the fundamental coaching points necessary to achieve a curved trajectory of the ball when observing and correcting technique.

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