Is the tackle technique associated with peak head inertial kinematics in elite female rugby league players?

Introduction: Women are embracing participation in collision sports such as rugby league, with participation rates increasing substantially since 2017. In 2018 a professional women’s league (the NRLW) was established. Despite this growth in the women’s game, there has been a limited amount of research conducted in the women’s rugby league, with assumption made based on insights observed in the men’s game. For example, the tackle, an integral part of rugby league, occurs commonly, with players being involved in multiple physical collisions during a game. It is the game play event that is associated with the greatest risk for concussion. As such, this study aimed to evaluate the tackle and identify factors that predict head impact of the ball carrier and the tackler when performing a front-on one-on-one tackle. Methods: The 3D kinematics of 17 professional women’s rugby league players (NRLW) performed front-on one-on-one tackles; whole-body kinematics were recorded with a 3D motion capture of both the ball carrier and tackler. Participants were instructed to perform their two self-selected ‘tackle types’, a smoother (upper/mid torso) and dominant (mid/lower torso) tackle that they typically perform in-game, at either a 6m (slow) or 12m (fast) tackle distance and speed. Video coding and 3D analysis was completed, and variables inputted into a generalised linear mixed model (p>0.05) to determine 3D tackle technique categories that estimate inertial head kinematics. Results: The tacklers’ peak angular and linear head acceleration were predicted by the (i) tackle type, (ii) the speed of tackler and (iii) if it was viewed that the tacklers head made contact with the ball carriers’ body. If it was observed that ball carrier displayed visual signs of whiplash (i.e., poor head control) it predicted their peak angular and linear head acceleration with the tackle type also predicted the ball carriers peak linear head acceleration. Discussion: This study offers valuable insights into the 3D tackle kinematics in elite women's rugby league, which could inform injury prevention and performance strategies. Our findings revealed a significant increase in peak head kinematics when the tacklers head made contact with the ball carriers’ body (e.g., head-shoulder, head-hip), and an inverse relationship with tackle types with dominant tackles resulting in higher peak head accelerations for the tackler but lower for the ball carrier. Impact/Application to the field: These results suggest that coaches may need to instruct tacklers differently to reduce inertial head kinematics by coaching their players when tackling to keep their head position outside the ball carriers’ body to avoid body contact during a tackle. When the ball carrier displayed whiplash when being tackled it predicted high peak had acceleration, and this poor head control suggests inefficient force dissipating during the tackle. Identification of whiplash of the ball carrier could be a coaching cue coaching to encourage their ball carriers to modify their bracing and evasion strategies to reduce their injury risk and improve performance. This information can then inform the development of evidence-based interventions tailored to the specific needs of female athletes and promote gender equity in sport and exercise science research. Declaration: My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.