Abstract

The ability to determine ball direction in advance is a key constraint on goalkeeping performance when facing penalty kicks in association football. In this communication we examined whether the positioning of the goalkeeper on the goal line might reduce the uncertainty of the shooting direction of the penalty kicker. Twelve male (M=20, SD=2 y old) players (8 field players and 4 goalkeepers) performed 168 penalty kicks when facing goalkeepers who took up 21 different positions on the goal line (varied from the left post (−3.3 m) to the right post (3.3 m), manipulated in increments of 0.33 m). According to the shooting angle of the kicks, we divided the goal into 5 different areas: (1) −18° (left post) to −10.8°, (2) 10.8° to −3.6°, (3) −3.6° to 3.6°, (4) 3.6° to 10.8° and (5) 10.8° to 18° (right post). Outfield players aimed to score goals, while goalkeepers were asked to save the goal, maintaining their position until the ball was shot. Uncertainty of shooting direction was assessed by using Shannon's entropy measure for N=5 possible outcomes. Results showed that when goalkeepers were positioned at −0.66 m, uncertainty of shooting direction was higher (2.1) than when they were positioned at −0.33 m, 0 m, 0.66 m and 0.99 m (1.8). However, when goalkeepers were positioned at 0.33 m, uncertainty seemed to decrease to 1.5. These data suggest that the goalkeeper's positioning in the goal constrained the level of uncertainty in the direction of shooting in penalty kicks in association football. More precisely, it appears that, when the goalkeeper is positioned 0.33 m to the right of centre in the goal, this spatial location might increase the ability to determine ball direction in advance. Further research needs to examine the relation between the distance required for a goalkeeper to intercept the ball and the uncertainty in shooting direction.