其他摘要：The purpose of this study was to analyze the informational constraints that influence the dynamics of 1v1 situations in football, from an ecological dynamics perspective. Participants were six, U13 level football players (Mean age: 11.8±0.4 yrs), who performed 5 1 v 1 trials each at four different start distances (1, 1.5, 2 and 2.5 meters) between the defender and the ball (5 repetitions x 6 players x 4 distances = 120 1v1 trials). We simulated performance constraints by creating a 1v1 competition. The task consisted of a representative situation in which the attacker tried to destabilize the dyad to create shooting opportunities, and the defender tried to maintain system stability by preventing the attacker from shooting. Players¿ motion was captured by digital video camera. For image treatment and to extract data on player movement coordinates, we used the TACTO 8.0 software, digitizing action at 25 Hz. The procedure consisted of following with the mouse the working point earlier tested After 7-days of training, the reliability of digitizing action was r=0.99 to x, and r=0.98 to y coordinates. After the calibration with real measures of six control points, the x and y coordinates of the players were extracted. Subsequently, data were analyzed with MATLAB software. Results showed no statistical differences for all outcome measures analyzed to discriminate differences between the various initial start distances (percentage of time spent in symmetry, anti-symmetry and undifferentiated state; time and distance to the end line of first and last phase transitions; and the number of zero crossings). We defined a potential order parameter as the proximity of the players to the goal in two qualitative states: (1) when the defender was nearer the end line than the attacker, and (2) when the attacker passed the defender and approached the end line. We analyzed the contribution of interpersonal distance and relative velocity to explain phase transitions that occurred between these coordinative states in 1v1 in football. We constructed plots with the time-series of these two control parameters candidates associated with the time-series of players¿ distance to the end line. Graphical inspection showed in all trials a clear tendency for greater relative velocity and lower interpersonal distance values during phase transitions between coordinative states. To confirm this interpretation, we computed a time-series analysis of Z-scores of relative velocity and interpersonal distance data, and a time-series analysis of Z-score differences between these variables. Mean data showed that maximum peaks in Z-score differences were related to all phase transitions. Results revealed could have several implications for training task design in team games. Players should be encouraged to explore the appropriated information to maintain/destabilize a 1v1 sub-system. At critical values of interpersonal distance, attackers can destabilize dyads by altering the difference between his/her velocity and the defender's velocity. We observed that the same physical variables constrained the dynamics of performer environment interactions despite variations in the initial start distances between players.
