Ball dynamics constrain interpersonal coordination in futsal
While ball kinematics are thought to constitute an important informational constraint on game behaviour in team sports (Davids et al., 2008; McGarry, 2009) they remain uninvestigated to date. Thus, a need exists to understand how ball dynamics constrain spatial-temporal behaviours of players, from consideration of the individual (player) through to the collective (team). This investigation addresses this issue of ball dynamics as a constraint on game behaviour by analyzing space-time relations between ball, players and teams kinematics. 2. METHODS Fifteen male senior players of the National Futsal University Team in Portugal participated in this study (M = 23.3 years, sd = 2.0 years and M = 11.5 years of
practice, sd = 1.3 years of practice), with each player giving informed consent before data collection. Participants were grouped into three teams of five players each. Futsal is a 5-a-side indoor soccer game that is played on a pitch of 40m length x 20m width. In this study, we investigated a particular sub-phase of a futsal game whereupon the goalkeeper of the trailing team is substituted late in the game for an extra outfield player with a view to increasing the chances of scoring a goal. Strategic goalkeeper substitution for the trailing team is commonly used by coaches during competitions. For instance, in the final four of the UEFA Futsal Cup in Lisbon, 2010, half of the goals that occurred in the last five minutes were scored using strategic goalkeeper substitution. We will refer to this futsal game condition as 5-v-4+GK.