Gemma Robinson

A weighted kappa statistic for reliability testing in performance analysis of sport

The kappa statistic has been used to evaluate the reliability of performance indicators measured using computerised notational analysis systems. However, all disagreements between observers are treated as total disagreements event if neighbouring values of ordinal scale performance indicators are used. Where nominal values are used to represent areas of the playing surface, kappa does not give any credit where the observers record neighbouring cells. Therefore, the purpose of the current paper was to illustrate how the weighted kappa statistic can be used with performance analysis data to give some credit where there are partial agreements between the observers.

A movement classification for the investigation of agility demands and injury risk in sport

The purpose of the current paper is to propose a movement classification scheme to be used when investigating injury risk from movement and agility demands of sporting activities. The method was tested and found to be operated with acceptable reliability by the authors. However, the method can be used more reliably for the analysis of soccer than it can for sports like tennis and netball where more direction changes and braking movements occur. The validity of the method was explored by applying it to 8 different cases from 7 different sports to ensure it covered the key events associated with agility demands and injury risk from movement within those sports. The method has over the advantage the Bloomfield Movement Classification is that different path change and turn types can be entered directly by the observer rather than having to be inferred through temporal analysis of the data. This also applies to acceleration and deceleration events although there are accelerations from non-stationary situations and decelerations to non-stationary situations not covered by the method. The method allows different sports and, indeed, different conditions within the same sport to be compared in terms of injury risk from movement and agility demands.

The effect of score-line on work-rate in English FA Premier League soccer

Investigations finding that soccer players perform more work when the score is level than when leading or trailing have not considered hat the significant effects were due to fatigue rather than score-line. For example, two teams may be level for the early part of a game and the score diverges later on. The current study established a typical fatigue pattern using data from 79 player performances during five 0-0 drawn English FA Premier League matches. This typical fatigue pattern was used to adjust the work-rate of 90 player performances in five English FA Premier League matches where both teams were level, ahead and behind for at least 15 minutes each. There was a significant interaction between player position and score-line (p = .010) with forwards spending a greater percentage of time moving at 4 m.s-1 or faster when their team was leading than when level while defenders spent a greater percentage of time moving at 4 m.s-1 or faster when their team was trailing than when level. An explanation for this interaction effect is that forwards feel encouraged to work harder when their team has earned a lead with the work-rate of opposing defenders also increasing as a result.

A Retrospective Evaluation Of Team Performance Indicators In Rugby Union

The purpose of this investigation was to demonstrate a method to validate a set of Performance Indicators (PIs). Data from one team (65 matches) was analyzed using 19 PIs categorized into six groups. Frequencies of each PI were recorded at 10- minute time intervals along with match outcomes (win/loss). Odds ratios (OR) derived from logistic regression (>2.0 or <0.5) were used to identify those PIs that contributed to match outcome. Eight PIs were subsequently identified: Ruck Quick had the largest positive effect on match outcome, within the first 20 minutes of the game and also within the 60-70 minute time interval; Territory (Intro 22) had a positive effect on match outcome, its impact was greatest in the first 20 minutes of the match. Two PIs from the Offence group (Gainline + and Gainline +P) had smaller positive effects on match outcome. Ruck Slow had the largest negative effect on winning a match for all time intervals. Other PIs that had negative effects on match outcome included turnover handling, ruck lost and turnover contact. Retrospective match data was used to investigate the efficacy of PIs. This post-hoc confirmation provides a framework for the assessment of PIs in performance analysis.

Score-line effect on work-rate in English FA Premier League soccer

This paper investigates the effect of score-line on work-rate in English FA Premier League soccer. Player movement data from 110 matches where a goal was scored between 15 minutes and the end of the first half were captured by the ProzoneTM player tracking system. The number of V-cut path changes performed per minute declined more after the first goal in matches that were won by one of the sides than in drawn matches (p < 0.017). V-cut path changes involve players changing direction more than 135° to the left or the right. There was also a significant interaction of match type (won, drawn or lost by the team scoring first), period of the match (before and after the first goal), venue and the relative quality of the teams on the total number of path changes performed (p < 0.05). Players from the scoring and conceding teams spent significantly less time in the middle third of the pitch after the first goal then before (p < 0.017). This suggests that variability in work-rate is influenced by a combination of factors. The results suggest that the first goal has an influence on teams’ tactics and work-rate. However, the study did not find any differences in work-rate between teams achieving different outcomes having scored first.

Asymmetry analysis of the arm segments during forward handspring on floor

Abstract Asymmetry in gymnastics underpins successful performance and may also have implications as an injury mechanism; therefore, understanding of this concept could be useful for coaches and clinicians. The aim of this study was to examine kinematic and external kinetic asymmetry of the arm segments during the contact phase of a fundamental skill, the forward handspring on floor. Using a repeated single subject design six female National elite gymnasts (age: 19 ± 1.5 years, mass: 58.64 ± 3.72 kg, height: 1.62 ± 0.41 m), each performed 15 forward handsprings, synchronised 3D kinematic and kinetic data were collected. Asymmetry between the lead and non-lead side arms was quantified during each trial. Significant kinetic asymmetry was observed for all gymnasts (p < 0.005) with the direction of the asymmetry being related to the lead leg. All gymnasts displayed kinetic asymmetry for ground reaction force. Kinematic asymmetry was present for more gymnasts at the shoulder than the distal joints. These findings provide useful information for coaching gymnastics skills, which may subjectively appear to be symmetrical. The observed asymmetry has both performance and injury implications.

Path changes and injury risk in English FA Premier League soccer

The purpose of the current investigation was to examine relationships between path changes performed by English FA Premier League soccer players, anthropometric variables and injuries reported. The study involved 25 players for whom typical path change performances were derived from at least six 90 minute matches. The players performed 39.9+13.2 sharp path changes to the side of the non-dominant leg which was significantly greater than the 35.4+12.7 sharp path changes made to the side of the dominant leg (p < .001). There was a negative association between height and the number of each type of path change (r < -.373) as well as a negative association between body mass and the number of each type of path change (r < -.287). There were no significant differences between the 10 players who missed at least one match through injury during the 2007-08 season and the 15 who did not for the frequency of any type of path change. Therefore, understanding the frequency of path changes alone is not sufficient to assess injury risk and it may also be necessary to examine the technique used when making path changes.

The effect of dismissals on work-rate in English FA Premier League soccer

The current paper studies the effect of dismissals on work-rate in English FA Premier League soccer. The study included 28 matches where a team had a player dismissed while they were winning by a single goal or the score was level. Two types of match were compared; matches where the team reduced to 10 players maintained the drawing or winning score-line until the end of the match and matches where they failed to do so. Similar reductions in work-rate variables were observed for teams reduced to 10 players and for their opponents after the dismissal irrespective of the outcome of the match. A significant interaction effect of team (the team reduced to 10 players v the team that played with 11 players throughout the match), match period (before v after the dismissal) and type of match was found on the percentage of time spent in the defending and attacking thirds (p < 0.05). The teams reduced to 10 players tended to spend more time in the defending third and less time in the attacking third after the dismissal. This pattern was observed to a greater extent in matches where the 10 players successfully maintained or improved the score between the dismissal and the end of the match. This suggests that outnumbered teams played strategically to defend the match status, rationing their efforts after the dismissal.