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The serve location pattern of professional, Under-16 and Under-12 high performance male and female tennis players was examined. In general, male players tended to serve more to the corners of the service box, while female players hit more serves to their opponent's body. An examination of points won through service aces and service winners indicated that male professional players won points on first serve on the deuce side of the court by serving to their opponents' backhand, and female professional players more won points on first serve by serving to the opponent's body. The findings will focus the coaching of serve performance in youth tennis players, and encourage the charting of tennis match performance to enhance player-coach discussion of tactical tendencies that are gender and age-specific.

{Heading: information constraints in dyad system] Word count: 4814 Keywords: ecological dynamics, informational constraints, time to contact, dyadic systems, association football, elite goalkeepers 2 AbstractThe aim of this study was to examine whether perceptual variables can provide informational constraints for the goalkeepers to intercept the ball successfully in 1v1 dyads.Video images of 42 actions (1v1 in direct shots) were selected randomly from different matches and divided into conceded goals (n=20) and saved actions (n=22) to investigate interceptive actions of 20 goalkeepers in the English Premier League in season 2013-2014.Time to Contact (TTC) of the closing distance gap between shooter and goalkeeper was obtained by digitising actions in the 18-yard penalty box. Statistical analyses revealed that, in sequences of play resulting in an intercepted shot at goal, goalkeepers closed down outfield players in the X axis, whereas when a goal was conceded, there was a significantly delayed movement by goalkeepers toward the shooters in this plane. The results of canonical correlations showed that a decreasing distance between a shooter and goalkeeper, and accompanied reduction in relative interpersonal velocity followed a temporal pattern.Findings of this study showed how perception of key informational constraints on dyadic system relations, such as TTC, interpersonal distance and relative velocity, constrain elite goalkeepers' interceptive actions, playing an important role in successful performance.3