Biomedical Engineering Reference
In-Depth Information
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=
.
right (p
175). These two situations present a
small wall (4 players) and a free kick kicked in the free zone of the goal. In other
terms, the lower performance can be explained, here, by the fact that a small wall
involves a large free area to cover by the goalkeeper. It is consequently much more
difficult for the goalkeeper to stop it.
0.01 except for fkR_5_wL, p
0
13.3.4 Discussion
The main goal of this case study is to analyze the influence of different wall position-
ing strategies on the goalkeeper performance. Results show that goalkeepers were
significantly less efficient in two situations: a wall of 4 players and a ball kicked in
the free zone of the goal. With 4 players in the wall, the free zone is wider and the
position of the goalkeeper is closer to the center of the goal. This situation is thus
very difficult for goalkeepers. Nevertheless, in the opposite case (5 players in the
wall and a ball kicked over it), the results of the goalkeepers are not that bad. This
result is startling since the free zone is smaller and the goalkeeper is farthest from the
center of the goal and even more from the opposite goalpost. Finally, looking at all
the situations, it thus seems that the goalkeeper should choose to place 5 players in
the wall. Notice that the side where the wall is aligned does not influence the ability
of the goalkeeper to intercept the ball.
Such an analysis of the goalkeeper's performance in front of different wall con-
figurations would not be possible without a Virtual Reality system that ensures a
complete freedom of movement of the goalkeeper. If a lot of studies have already
investigated this very popular sport, the large space of the pitch and the complex-
ity of the interaction make the experimentations difficult. If numerous studies have
explored the goalkeeper's performance during penalties [
46
,
47
], very few have ana-
lyzed the goalkeeper performance during free kick. Some interesting studies such as
those of Craig et al. [
19
,
20
] were focused on free kick in order to explore the percep-
tual skills of goalkeeper and to identify the optical variables that underlie judgments.
In these studies, the aim was to evaluate the influence of ball's effect on perception.
In the case study presented here, the goal is to evaluate the goalkeeper's performance
on the perception-action coupling. His movements are thus fundamental, to intercept
the ball of course but also to place the wall. The goalkeeper indeed must change his
viewpoint from one goalpost to the other to be able to align the wall depending on
the number of players in the wall and the position of the kicker. This kind of studies
can then not be done if no displacement in the virtual reality system is provided.
13.4 Conclusion
The two case studies presented in this chapter show how virtual reality can be used
to analyze the visual information uptake in sports duel. The first example deals
with the interception of a virtual attacker doing deceptive movements, by a real
