Injury epidemiology in male professional Rugby Union : player-specific injury analysis and its application to starter and replacement players

This thesis investigated the epidemiology of injuries in professional Rugby Union and the methods in which they are analysed and reported. Furthermore, the thesis explored the development and application of a player-specific method of analysing injuries. Chapter 3 investigated match injuries within the Welsh regional professional Rugby Union teams, demonstrating a higher incidence than previously reported in professional Rugby Union (99.1 injuries/1000 match hours). In addition, the highest proportion of injuries in matches were sustained during the tackle event (50-63%). Whilst this study followed the recommendations of the consensus statement, Chapter 4 aimed to identify whether research in elite or professional sports with published consensus statements also follow their respective recommendations. Chapter 4 demonstrated that there remain inconsistencies with regards to reporting injuries, identifying that the pooling of injury data across individuals remains a common issue within research. As this method is recommended by the consensus statement on data collection and analysis procedures within Rugby Union, Chapter 5 explored a player-specific approach to analysing and reporting injuries. The consensus statement method of calculating team-level exposure, using the standard number of players in a team and standard match length, was compared against the use of global positioning systems (GPS) to identify if the consensus statement provides an adequate method of analysing injury incidence. Interestingly, there were differences between the injury incidence calculated using standard match length and the injury incidence using GPS-derived exposure hours (59.5 vs 95.7 injuries/1000 match hours, respectively). While the team-level injury incidence was influenced by the number of players providing consent, the study demonstrated that team-level injury incidence does not reflect the variation in injury rates at a player-specific level, with 94% of players falling outside of the 95% confidence intervals for the team-level injury incidence. In addition, an alternative to injury incidence statistic was explored through analysing the probability of injury. This identified that when players at the same incidence are exposed to higher match hours, they have a higher probability of incurring multiple injuries. The player-specific methods of analysis from this Chapter were applied in Chapter 6, where the injury rates and mechanisms of starter and replacement players were analysed. Chapter 6 identified that starters had a higher injury incidence than replacement players (80.8 vs 57.2 injuries/1000 match hours, respectively). When accounting for the number of replacements used in a match, the injury rate per player exposure did not change for each number of replacements used. However, the number of replacement players had a significant effect on the number of match injuries, where injuries increased by 12% per replacement used (p = 0.037). This increase may, in part, be due to a small number of matches using less than seven replacements (20%). Therefore, further analysis accounting for the replacement time-in-game was also implemented, showing a non-significant 1% increase in injury for every 10 minutes of replacement player time-in-game (p = 0.099). Chapter 6 also identified that the tackle event was the mechanism responsible for the highest proportion of injuries for both starter and replacement players. The propensity for injury was similar for tackles involving two starters or two replacements, with a higher injury propensity only shown when an injured starter was tackling a replacement ball carrier. Starter and replacement players exhibited different characteristics during an injury inciting tackle, specifically when the injured player was making a tackle. Replacement players maintained a lower body position, predominantly using a shoulder tackle and contacting the upper leg of the ball carrier. In contrast, starters demonstrated a higher body position, contacting the ball carriers head whilst in an upright position. This thesis demonstrated that whilst consensus statements are important for the consistent definition and data collection associated with injury surveillance, there remains inaccuracies and inconsistencies with the way data is analysed and reported. The lack of research reporting the subsequent injuries fails to consider the potential for multiple injury occurrence at a player specific level. Furthermore, the continued pooling of data across individuals within a team (team-level injury incidence) fails to account for the variation in injury rates at a player-specific level. This is emphasised further when player-specific analysis is applied to starter and replacement players. The application of a player-specific analysis demonstrated that current regulations associated with the use of replacement players within matches is appropriate. Importantly, however, the analysis of tackle characteristics at a player-specific level demonstrated differences in injury inciting tackle characteristics between players. Where possible, methods such as GPS-derived exposure and probability analysis should be incorporated within injury surveillance to provide a more comprehensive player-specific analysis of injury that can aid in injury management and improve player welfare. In addition, injury risk mitigation strategies associated with the tackle should incorporate a player-specific approach, specifically considering the type of player (i.e. starter or replacement player) used within matches.