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A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball

Free kicks are an important goal scoring opportunity in football. It is an unwritten rule that the goalkeeper places a wall of defending players with the aim of making scoring harder for the attacking team. However, the defensive wall can occlude the movements of the kicker, as well as the initial p...

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Autores principales: Valkanidis, Theofilos Ch., Craig, Cathy M., Cummins, Alan, Dessing, Joost C.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7774851/
https://www.ncbi.nlm.nih.gov/pubmed/33382753
http://dx.doi.org/10.1371/journal.pone.0243287
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author Valkanidis, Theofilos Ch.
Craig, Cathy M.
Cummins, Alan
Dessing, Joost C.
author_facet Valkanidis, Theofilos Ch.
Craig, Cathy M.
Cummins, Alan
Dessing, Joost C.
author_sort Valkanidis, Theofilos Ch.
collection PubMed
description Free kicks are an important goal scoring opportunity in football. It is an unwritten rule that the goalkeeper places a wall of defending players with the aim of making scoring harder for the attacking team. However, the defensive wall can occlude the movements of the kicker, as well as the initial part of the ball trajectory. Research on one-handed catching suggests that a ball coming into view later will likely delay movement initiation and possibly affect performance. Here, we used virtual reality to investigate the effect of the visual occlusion of the initial ball trajectory by the wall on the performance of naïve participants and skilled goalkeepers. We showed that movements were initiated significantly later when the wall was present, but not by the same amount as the duration of occlusion (~200ms, versus a movement delay of ~70-90ms); movements were thus initiated sooner after the ball came into view, based on less accumulated information. For both naïve participants and skilled goalkeepers this delayed initiation significantly affected performance (i.e., 3.6cm and 1.5cm larger spatial hand error, respectively, not differing significantly between the groups). These performance reductions were significantly larger for shorter flight times, reaching increased spatial errors of 4.5cm and 2.8cm for both groups, respectively. Further analyses showed that the wall-induced performance reduction did not differ significantly between free kicks with and without sideward curve. The wall influenced early movement biases, but only for free kicks with curve in the same direction as the required movement; these biases were away from the final ball position, thus hampering performance. Our results cannot suggest an all-out removal of the wall–this study only considered one potential downside–but should motivate goalkeepers to continuously evaluate whether placing a wall is their best option. This seems most pertinent when facing expert free kick takers for whom the wall does not act as a block (i.e., whose kicks consistently scale the wall).
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spelling pubmed-77748512021-01-07 A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball Valkanidis, Theofilos Ch. Craig, Cathy M. Cummins, Alan Dessing, Joost C. PLoS One Research Article Free kicks are an important goal scoring opportunity in football. It is an unwritten rule that the goalkeeper places a wall of defending players with the aim of making scoring harder for the attacking team. However, the defensive wall can occlude the movements of the kicker, as well as the initial part of the ball trajectory. Research on one-handed catching suggests that a ball coming into view later will likely delay movement initiation and possibly affect performance. Here, we used virtual reality to investigate the effect of the visual occlusion of the initial ball trajectory by the wall on the performance of naïve participants and skilled goalkeepers. We showed that movements were initiated significantly later when the wall was present, but not by the same amount as the duration of occlusion (~200ms, versus a movement delay of ~70-90ms); movements were thus initiated sooner after the ball came into view, based on less accumulated information. For both naïve participants and skilled goalkeepers this delayed initiation significantly affected performance (i.e., 3.6cm and 1.5cm larger spatial hand error, respectively, not differing significantly between the groups). These performance reductions were significantly larger for shorter flight times, reaching increased spatial errors of 4.5cm and 2.8cm for both groups, respectively. Further analyses showed that the wall-induced performance reduction did not differ significantly between free kicks with and without sideward curve. The wall influenced early movement biases, but only for free kicks with curve in the same direction as the required movement; these biases were away from the final ball position, thus hampering performance. Our results cannot suggest an all-out removal of the wall–this study only considered one potential downside–but should motivate goalkeepers to continuously evaluate whether placing a wall is their best option. This seems most pertinent when facing expert free kick takers for whom the wall does not act as a block (i.e., whose kicks consistently scale the wall). Public Library of Science 2020-12-31 /pmc/articles/PMC7774851/ /pubmed/33382753 http://dx.doi.org/10.1371/journal.pone.0243287 Text en © 2020 Valkanidis et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Valkanidis, Theofilos Ch.
Craig, Cathy M.
Cummins, Alan
Dessing, Joost C.
A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title_full A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title_fullStr A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title_full_unstemmed A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title_short A goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
title_sort goalkeeper’s performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7774851/
https://www.ncbi.nlm.nih.gov/pubmed/33382753
http://dx.doi.org/10.1371/journal.pone.0243287
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