Analysis of ball carrier head motion during a rugby union tackle without direct head contact: A case study

Abstract

Rugby union players can be involved in many tackles per game. However, little is known of the regular head loading environment associated with tackling in rugby union. In particular, the magnitude and influencing factors for head kinematics during the tackle are poorly understood. Accordingly, the goal of this study was to measure head motion of a visually unaware ball carrier during a real game tackle to the upper trunk with no direct head contact, and compare the kinematics with previously reported concussive events. Model-Based Image-Matching was utilised to measure ball carrier head linear and angular velocities. Ball carrier componential maximum change in head angular velocities of 38.1, 20.6 and 13.5 rad/s were measured for the head local X (coronal plane), Y (sagittal plane) and Z (transverse plane) axes respectively. The combination of a high legal tackle height configuration and visually unaware ball carrier can lead to kinematics similar to average values previously reported for concussive direct head impacts. AbstractRugby union players can be involved in many tackles per game. However, little is known of the regular head loading environment associated with tackling in rugby union. In particular, the magnitude and influencing factors for head kinematics during the tackle are poorly understood. Accordingly, the goal of this study was to measure head motion of a visually unaware ball carrier during a real game tackle to the upper trunk with no direct head contact, and compare the kinematics with previously reported concussive events. Model-Based Image-Matching was utilised to measure ball carrier head linear and angular velocities. Ball carrier componential maximum change in head angular velocities of 38.1, 20.6 and 13.5 rad/s were measured for the head local X (coronal plane), Y (sagittal plane) and Z (transverse plane) axes respectively. The combination of a high legal tackle height configuration and visually unaware ball carrier can lead to kinematics similar to average values previously reported for concussive direct head impacts.

Force experienced by the head during heading is influenced more by speed than the mechanical properties of the football

“…35 Human body models could be further validated for sports impacts using motion capture laboratory trials and/ or real-world impact modeling using multiple camera view video footage. [36][37][38] The model used in this study is a passive model, and hence, active neck muscles could not be simulated or assessed. The development of active human body models has become a promising prospect in sport impact analysis.…”

3D Biomechanics of Rugby Tackle Techniques to Inform Future Rugby Research Practice: a Systematic Review

“…Technological advances in 3D motion capture technology offer the potential for in-game rugby-style tackle technique to be assessed in future research. Model-based image matching is one such emerging technology that uses multiple 2D video camera views and applies a multibody skeletal model to estimate ingame 3D player kinematics [51] or 3D head velocity Reference [22] reported data as medians and upper and lower quartiles [23]; reported as absolute median (25% and 95% confidence interval) [25]; reported data as mean ± SD/SEM or as a mean and an effect size [26]; reported data as mean ± SD [27]; reported data as mean (95% confidence interval) or as r [28]; reported data as either mean (95% confidence interval) or odds ratio (95% confidence interval) or as a mean during a tackle in rugby union [52] and American football [53]. This manual process also takes 60 h to complete a single case study [54].…”

“…Markerless image processing technology to estimate 3D joint angles is valid [51] but not 3D head velocity [54]. It is recommended that due to the low sampling rate of the broadcast video of 100 Hz [54] or game video footage of 25 Hz in rugby union [52] or 60 or 120 Hz in American football [53], neither head velocity nor acceleration should be calculated from broadcast video as its low sampling rate violates Nyquist sampling theorem based on spectral analysis. An alternative technology measuring head acceleration is wearable sensors such as instrument mouthguards [55].…”

The role of player mass and contact speed on head kinematics and neck dynamics in rugby union tackling

“…45 These could be gained from motion capture laboratory trials and/or real-world impact modeling using multiple camera view video footage. [46][47][48] Given the above, contextualizing the results in terms of direct injury risk is a challenge. Additionally, neck injury criterion are typically based on vehicle impacts and may have limited applicability to non-automotive scenarios.…”