Biomedical Engineering Reference
In-Depth Information
Two case studies are presented below to illustrate this kind of studies but imply-
ing moreover large displacements of the immersed subject. The first example shows
a duel between a real rugby defender and a virtual attacker who makes deceptive
movements (case study 1). The defender must thus perform medio-lateral displace-
ments to intercept the attacker. This study is based on an HMD technology to allow
the defender to move. The second case study examines the performance of a soc-
cer goalkeeper against a free kick depending on the configuration of the wall (case
study 2). The goalkeeper has to dive as in real situation to intercept the ball.
13.2 Case Study 1: Deceptive Movements in Rugby
In rugby, the aim is to progress with a ball, toward the opposite team for scoring
a try after the goal-line. In order to win, each team must thus develop individual
and collective displacements to avoid being intercepted by opponents. The main
difficulty for the defender is to intercept a human and not an object (such as a ball)
that could follow a predefined trajectory. Indeed, a rugby attacker has the opportunity
to suddenly change his running direction at every moment. This is precisely what
happens during a deceptive movement of an attacker. If such motor strategies are
very used during sports interaction, few studies investigated them [ 18 , 33 , 48 ].
The wealth of the rugby duel is this opportunity for an attacker to play with
deceptive and non-deceptive movements to take the advantage over a defender. The
goal of this case study is to explore this complex interaction and more precisely
how a defender expert, compared to a novice one, reacts to a deceptive movement
of an attacker? For analyzing such strategies, a controllable and repeatable stimuli
(attacker movement) as well as a system allowing free displacements of the real
defender is necessary. Virtual reality is the solution.
13.2.1 Setup
In this experiment, deceptive (DM) and non-deceptive (NDM) movements were
presented to novice and expert defenders. The goal of the immersed defender is
to stop the attacker. The virtual reality system described in this section allows the
displacement and freedomofmovement of the defender to achieve his task (Fig. 13.2 ).
Real 1 attacker versus 1 defender actions were recorded using the optoelectronic
motion capture Vicon MX system. Eight rugby players (age 21.38
1.18 years) who
played in the French national league took part in the motion capture session. The
aim for the attacking player was the same as in the game of rugby: the attacker had
to try to beat the defender whilst the defender had to try to stop the attacker. Both
deceptive (DM—changing running direction to beat the defender) and non-deceptive
(NDM—not changing running direction to beat the defender) were recorded [ 15 ].
These captured movements were then used to animate a virtual rugby player by using
±
 
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