Influence of the frame of reference on head acceleration events recorded by instrumented mouthguards in community rugby players

Abstract

ObjectivesTo highlight the need for standardisation in the communication of head impact telemetry from instrumented mouthguards (iMG). The purpose of this study is to examine how the frame of reference for reporting head acceleration events (HAE) may affect the interpretation of head impacts recorded from iMGs in community rugby players.MethodsAn analytical investigation of 825 video verified HAEs recorded from male community players during 5 rugby match exposures. HAEs were captured with an iMG, known to be reliable and valid for this purpose. The linear and angular head acceleration at the centre of mass (head_CG) was calculated from filtered iMG accelerometer and gyroscope data, and the location of impact was estimated. The iMG and head_CG data were examined for systematic bias, geometric differences and the degree of concordance. Finally, mixed model analyses were fitted to assess the differences in peak resultant acceleration (PLA) by impact locations and directions of head motion while controlling for intra-athlete correlations.ResultsThe degree of concordance between the iMG versus head_CG measures varied by impact location. The mixed model confirmed differences in the PLA by location (F(8,819) = 16.55, p<0.001) and by direction of head motion (F(5,417) = 7.78, p<0.001).ConclusionThe head acceleration reported at the iMG is not proportional to measurements that have been transformed to the head_CG. Depending on the impact location and direction of head motion, the acceleration measured at the iMG may overestimate, underestimate or miss entirely the PLA with respect to the head_CG. We recommend standardising the reporting of iMG data within the head_CG frame of reference.

Head Acceleration Events During Tackle, Ball‐Carry, and Ruck Events in Professional Southern Hemisphere Men's Rugby Union Matches: A Study Using Instrumented Mouthguards

“…This finding concurs with recent literature demonstrating that most injuries sustained during professional rugby union match play occur during tackles [2,3]. Similarly, research in community level rugby union demonstrated that 66%-75% of iMG-recorded HAE occurred during tackles and ball carries [20]. However, the finding that the defensive ruck probability profile was more comparable with tackles than attacking rucks is novel.…”

“…Importantly, although the probabilities of HAE max were similar, players are involved in different numbers of contact events per match due to positional demands (e.g., forwards are involved in approximately double the number of tackle events than backs per match [1]), so the absolute HAE exposure for each contact event will differ between positions. Indeed, in senior community [20] and senior professional male [15] rugby union players, research has demonstrated a greater incidence of HAEs in forwards than backs. Given that the cumulative exposure to head accelerations across a playing career may have consequences for long-term brain health [9], future research should build upon the probability profiles by including details of the absolute exposure to each contact event.…”

“…Previous literature has utilized both distributions. One study analyzed the truncated distribution of iMG data aggregated at a count level (i.e., counts of iMG-recorded HAE in a specific magnitude range) [20], thus values not recorded were not considered in the analysis, limiting the opportunity to consider contact-event characteristics. Another study considered individual iMG observations within a censored distribution, assuming that all not recorded observations fell below an arbitrary value (10g and 1000 rad/s 2 ), and data were not modeled to account for the multilevel data structure [15].…”

Head Acceleration Events in Male Community Rugby Players: An Observational Cohort Study across Four Playing Grades, from Under-13 to Senior Men

“…All post-processing and data reduction were performed using purpose-written MATLAB routines (R2021b, MathWorks Inc., California, USA). The raw linear acceleration and angular velocity data from the iMG accelerometer and gyroscope were imported into MATLAB and filtered using a 200 Hz low-pass fourth-order Butterworth filter [ 28 ]. The filtered data were then transformed into the head centre of mass (COM).…”

Prospective cohort study of long-term neurological outcomes in retired elite athletes: the Advanced BiomaRker, Advanced Imaging and Neurocognitive (BRAIN) Health Study protocol

“…Participation in professional contact sports with repetitive head impacts has also been reported to increase the risk of developing motor neuron disease 33. The degree of exposure to repeated head impacts can be estimated by assessing the playing history of a player, including years of play and playing position, as well as the number of concussions reported or identified,34–36 or via the development of an exposure matrix based on measurements from instrumented mouthguards 37 38…”