Informational constraints on interceptive actions of elite football goalkeepers in 1 v1 dyads during competitive performance

The 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

Validation of Match Notation (A Coding System) in Tennis

The aim of this study was to establish the reliability and validity of a coding system for measuring serve and return of serve locations in tennis. A notational analysis of mens and womens singles matches at the 2008 Australian Open was undertaken. The results revealed that the inter-rater reports were highly similar on first or second serve (r=0.972), serve landing location (r=0.999), returners impact location (r=0.990) and return of serve landing location (r=0.995). Hawk-Eye data were used to validate the coding measures for ball location. When comparing the coded ball location data of the researcher (n=1) and tennis coaches (n=4) to Hawk-Eye data, high correlations for the landing location of the serve (r=0.998), the impact location of the return (r=0.993) and the landing location of the return of serve (r=0.997) were registered. The match notation system analysed was shown to be reliable and valid for the study of serve and return of serve strategies and tactics in tennis. This system also provides a template for other researchers and coaches to evaluate game tactics in tennis.

A comparative analysis of the spatial distributions of the serve return

The execution of the serve return is of particular importance given the increasing serve speeds that characterise modern tennis. The spatial distributions of the serve return at the professional level and between two age groups of high performance players (i.e., Under-16 and Under-12) were analysed to determine whether the location of a serve-return was independent of or related to, the gender of the player. Chi-square analysis revealed significant differences in the distribution of first serve-return across the three serve-return locations to wide serves between the male and female Under-16 players (p< .001) and between the male and female Under-12 players (p< .001). When only points won by the returner were considered, no relationship was found between locations of serve-returns and winning the point of the male and female professional, Under-16 and Under-12 players. It was also revealed that professional players attacked second serves by directing second serve returns to the corners of the court These findings aid coaches to value how the serve-return strategies of players may evolve with age and vary with gender — in line with variables of technical skill development and the game's temporal demands