Rugby league ball carrier injuries: The relative importance of tackle characteristics during the European Super League

Abstract

Rugby league carries a high injury incidence with 61% of injuries occurring at tackles. The ball carrier has a higher injury incidence than the defender, therefore understanding mechanisms occurring during injurious tackles are important. Given the dynamic, open nature of tackling, characteristics influencing tackle outcome likely encompass complex networks of dependencies. This study aims to identify important classifying characteristics of the tackle related to ball carrier injurious and non-injurious events in rugby league and identify the characteristics capability to correctly classify those events. Forty-one ball carrier injuries were identified and 205 matched non-injurious tackles were identified as controls. Each case and control were analysed retrospectively through video analysis. Random forest models were built to 1.) filter tackle characteristics possessing relative importance for classifying tackles resulting in injurious/non-injurious outcomes and 2.) determine sensitivity and specificity of tackle characteristics to classify injurious and non-injurious events. Six characteristics were identified to possess relative importance to classify injurious tackles. This included 'tackler twisted ball carrier's legs when legs were planted on ground', 'the tackler and ball carrier collide heads', 'the tackler used body weight to tackle ball carrier, 'the tackler has obvious control of the ball carrier' 'the tackler was approaching tackle sub-maximally' and 'tackler's arms were below shoulder level, elbows were flexed'. The study identified tackle characteristics that can be modified in attempt to reduce injury. Additional injury data are needed to establish relationship networks of characteristics and analyse specific injuries. Sensitivity and specificity results of the random forest were 0.995 and 0.525.

Tackle and ball carrier demands of rugby league: a seven-year league-wide study including over 1,000,000 tackle events

“…This rule change allowed the referee to award six more tackles in the event of an infringement by a defending side. As such governing bodies should be aware of the impact rules changes have on match activities, specifically tackle events, given their injury 11 and concussion risk 27 . Gardner 28 demonstrated that, during NRL match play, 94.5% of head injury assessments (HIAs) occurred during the tackle event and reported 1.6 HIAs per 1000 tackler involvements.…”

“…Match-play event data was provided by Opta (Stats Perform, London, United Kingdom) and extracted online (https://www.optaprorugby.com/index.php) as an extensible markup language (XML) file. Commercial match-event providers have been used extensively as a data source within rugby league research 11,[15][16][17][18] . Each XML file was converted to a comma separated value (CSV) file that contained date, a unique fixture identification number (ID), player ID, position category, event ID, event timestamp, and event type (e.g., ball carry or tackler involvements).…”

“…Consequently, the peak ball carry and tackle demands of rugby league match-play remain unknown and requires investigation. This is important given 61% of injuries during rugby league occur during the tackle event 11 , and the ball carrier has a higher injury rate than the tackler 4 .…”

Are rugby league players involved in more tackles than normal, prior to an injury sustained during a tackle event?

“…A number of studies have explored factors associated with injurious tackle-events in rugby league (King, Hume and Clark, 2012b;Gardner et al, 2015;Hopkinson et al, 2020). Tackle characteristics such as initial contact with the shoulder or mid-torso (King, Hume and Clark, 2012a;Gardner et al, 2015), head on head collision and the tackler twisting the ball carrier's legs (Hopkinson et al, 2020) were found to have the greatest association with injury.…”

“…A number of studies have explored factors associated with injurious tackle-events in rugby league (King, Hume and Clark, 2012b;Gardner et al, 2015;Hopkinson et al, 2020). Tackle characteristics such as initial contact with the shoulder or mid-torso (King, Hume and Clark, 2012a;Gardner et al, 2015), head on head collision and the tackler twisting the ball carrier's legs (Hopkinson et al, 2020) were found to have the greatest association with injury. However, to date research in rugby league has mainly focused on the tackle-event in which the injury occurred (King, Hume and Clark, 2012a;Gardner et al, 2015;Hopkinson et al, 2020), with minimal consideration of what has occurred prior to the injurious tackle-event.…”