Rugby Union is a high-intensity intermittent sport that involves numerous phases of open play, separated by contact situations. The initial phase of play typically starts from a set-piece (e.g. scrum, lineout or kick-off), where the defensive team arranges itself in a horizontal line called the defensive line. The arrangement of the defensive line and the movement of this line during play is often in response to the movement and alignment of the attacking line (Hendricks et al., 2013). The ability of the attacking team to break through the defensive line is a key indicator of success as it creates opportunities to score tries (Bracewell, 2003; Wheeler et al., 2010; Diedrick and van Rooyen, 2011).
A study by Wheeler et al. (2010) identified three effective attacking strategies to break through the attacking line--tackle breaks, offloads and line breaks. A coordinated set of skills need to be executed effectively to achieve these attacking strategies. The set of skills associ ated with tackle breaks and offloads have been documented (Wheeler and Sayers, 2009; Wheeler et al., 2010). Similarly, effective defensive skills and tackle techniques have also been identified (Hendricks et al., 2014). However, not much is known about the skills associated with line breaks.
In an analysis of 58 Six Nations Rugby games between 2003 and 2007, Ortega et al. (2009) observed that successful teams break the line more frequently than unsuccessful teams. This suggests that line breaks are a key performance indicator of successful teams. Logically, the next step would be to describe the events, technical skills and situation in which line breaks occur. This will assist coaches in designing attacking drills to improve player's skills and increase their chances of breaking the line in matches. Analysing the technical skill requirements for a line break, in addition to the events leading up to the line break and the situation in which the line break occurs provides a better understanding of the conditions for successful match performances (Mackenzie and Cushion 2013). Therefore, the primary aim of this study was to analyse the technical skills and match situations that led to line breaks in Rugby Union. A secondary aim was to determine which technical skills and situations influenced the outcome of the line break.
All matches (n = 125) of the 2013 Super Rugby competition were analysed. The 2013 Super Rugby competition was a professional men's Rugby Union competition played between 15 franchises from Australia, New Zealand and South Africa. The footage was obtained from publically broadcasted matches that were recorded and saved onto a database. The study was ethically approved by the University of Cape Town Faculty of Health Sciences Human Research Ethics Committee (HREC REF: 559/2014). The recorded matches were analysed using Sports Code Elite Version 6.5.1 on an Apple iMac (Apple, USA) displayed at eye level. The analysis software allowed for the control of time lapse during the recorded match and the recording and saving of each event into a database. The analyst was able to pause, rewind and watch the footage in slow motion. The highest frequency at which the analyst could slow down the footage was 25 frames per second (25 Hz).
Line breaks were identified using the following criteria. Note, all of the criteria described below had to be fulfilled for an event to be classified as a line break.
The player in possession of the ball (i.e., ball-carrier) needed to visibly move through a straight line between two defenders in the defensive line or between a defender and the touchline, regardless of the shape and a defender and the touchline, regardless of the shape and-movement of the defensive line, and without being physically contacted by a defender (Gilmore, 2006; Wheeler et al., 2010; Hendricks et al., 2013).
The defensive line needed to consist of at least two players moving in unison. After an attacker penetrated the defensive line, at least one defender from the defensive line was required to turn toward the ball-carrier, in an attempt to chase the ball-carrier. This criterion allowed for the distinction between half breaks and complete line breaks (Burt et al., 2013).
The ball-carrier needed to receive the ball from a teammate before he breached the line. This criterion excluded interceptions and offloads from the analyses. When the starting phase was a turnover or loose ball, the line break could not occur in that phase of play, as it was deemed the defensive line would not have sufficient time to form.
A total of 362 line breaks were identified, with an average of 3 (SD = 2) line breaks per match. Thereafter, each line break was coded for match, situational and technical descriptors that preceded the line break. The analysis of the line break began at the first set-piece, or change in possession, preceding the line break and ended if possession of the ball was lost, a break in open play after the line break occurred, when the ball went into touch, an infringement occurred or if a try was scored.
The purpose of the descriptors was to adequately describe the technical skills which led to a line break. The descriptors needed to possess objective metric properties and a valid means of interpretation (O'Donoghue, 2010). The list of descriptors used to code the line breaks was created through the use of previous peer-reviewed published literature (Hendricks et al., 2014; Wheeler et al., 2010) and by identifying and describing characteristics required specifically for this study. The list was then reviewed by a panel of coaches, sports scientists and rugby administrators to assess the validity and relevance of the performance indicators, and the clarity of their definitions.
In line with the purpose of the study, the variables were divided into five categories: match situation, pre-line break characteristics, final phase characteristics, skills and post line break outcomes (Tables 1-3). The match situation descriptors described factors related to the teams playing in the match. The pre-line break characteristics described the events that occurred in the phases leading up to the line break, and final phase characteristics, the events in the phase that the line break occurred. Post line break outcomes described the results of the line break, in terms of possession and tries scored. The list of descriptors selected for this study was inclusive to account for any factor which may be relevant. However, for the purpose of this paper, only the variables which were found to be influential will be discussed.
For intra-coder reliability, five randomly selected matches were coded twice using the variables and definitions described above. The coding of the same match was separated by a week (Wheeler et al., 2010). Kappa statistics (k) were used to test the intra-reliability of the coder for each...