An Initial Assessment of Head Acceleration Events in Rugby League using Instrumented Mouthguards and Qualitative Video Analysis

There is a growing concern that the long-term effects potentially associated with contact sport are not only caused by concussions, but by the accumulation of subconcussive impacts. It is therefore important to understand the head acceleration event (HAE) exposure sustained by contact sports individuals. In this thesis, a combination of qualitative video analysis and biomechanical instrumented mouthguard data is used to quantify and characterise HAE sustained by professional male rugby league players during competitive matches. Peak linear acceleration (PLA), peak angular acceleration (PAA) and peak change in angular velocity (ΔPAV) were collected using custom-fit instrumented mouthguards with an 8 g or 800 rad/s2 resultant data acquisition threshold. A total of 725 HAE were collected from 31 player matches throughout 10 male players. Multiple HAE often occurred in the same tackle phase and 47.6% of HAE occurred after the initial contact between a tackler and the ball-carrier. Indirect HAE accounted for around half of HAE from carries (50.4%) and a quarter of HAE from tackles (23.8%), they also led to significantly greater ΔPAV than direct HAE (p < 0.001, ES = 0.69, interpretation = moderate). Each kinematic was also skewed to lower values, therefore applying a data acquisition threshold of 10 g led to an exposure rate of around half (13.8 ± 6.9 HAE per player, per match) than the exposure rate reported using an 8 g or 800 rad/s2 threshold (28.0 ± 10.6 HAE per player, per match). The results and methodology from this study demonstrate the efficacy of a combination of biomechanical data with qualitative video analysis in quantifying and characterising HAE exposure in rugby league and will form the basis for a future league wide instrumented mouthguard study

Thinking like a man? The cultures of science

Culture includes science and science includes culture, but conflicts between the two traditions persist, often seen as clashes between interpretation and knowledge. One way of highlighting this false polarity has been to explore the gendered symbolism of science. Feminism has contributed to science studies and the critical interrogation of knowledge, aware that practical knowledge and scientific understanding have never been synonymous. Persisting notions of an underlying unity to scientific endeavour have often impeded rather than fostered the useful application of knowledge. This has been particularly evident in the recent rise of molecular biology, with its delusory dream of the total conquest of disease. It is equally prominent in evolutionary psychology, with its renewed attempts to depict the fundamental basis of sex differences. Wars over science have continued to intensify over the last decade, even as our knowledge of the political, economic and ideological significance of science funding and research has become ever more apparent

Instrumented mouthguards in elite-level men’s and women’s rugby union: characterising tackle-based head acceleration events

Objectives To examine the propensity of tackle height and the number of tacklers that result in head acceleration events (HAEs) in elite-level male and female rugby tackles.Methods Instrumented mouthguard data were collected from women (n=67) and men (n=72) elite-level rugby players from five elite and three international teams. Peak linear acceleration and peak angular acceleration were extracted from HAEs. Propensities for HAEs at a range of thresholds were calculated as the proportion of tackles/carries that resulted in an HAE exceeding a given magnitude for coded tackle height (low, medium, high) and number of tacklers. Propensity ratios with 952.7 (95.89 to 155.02) and 41.2 (95.22 to 184.58) propensity ratio to cause ball carrier HAEsgt;30 g compared with medium tackles for men and women, respectively. Low tackles had a 2.6 (95.91 to 3.42) and 5.3 (95.28 to 8.53) propensity ratio to cause tackler HAEsgt;30 g compared with medium tackles for men and women, respectively. In men, multiple tacklers had a higher propensity ratio (6.1; 95.71 to 9.93) than singular tacklers to cause ball carrier HAEsgt;30 g but a lower propensity ratio (0.4; 95.29 to 0.56) to cause tackler HAEsgt;30 g. No significant differences were observed in female tacklers or carriers for singular or multiple tacklers.Conclusion To limit HAE exposure, rule changes and coaching interventions that promote tacklers aiming for the torso (medium tackle) could be explored, along with changes to multiple tackler events in the male game.Data are available upon reasonable request. Anonymous data are available at a reasonable request to the corresponding author

Head Exposure to Acceleration Database in Sport (HEADSport): a kinematic signal processing method to enable instrumented mouthguard (iMG) field-based inter-study comparisons

Objective Instrumented mouthguard (iMG) systems use different signal processing approaches limiting field-based inter-study comparisons, especially when artefacts are present in the signal. The objective of this study was to assess the frequency content and characteristics of head kinematic signals from head impact reconstruction laboratory and field-based environments to develop an artefact attenuation filtering method (HEADSport filter method).Methods Laboratory impacts (n=72) on a test-dummy headform ranging from 25 to 150 g were conducted and 126 rugby union players were equipped with iMGs for 209 player-matches. Power spectral density (PSD) characteristics of the laboratory impacts and on-field head acceleration events (HAEs) (n=5694) such as the 95th percentile cumulative sum PSD frequency were used to develop the HEADSport method. The HEADSport filter method was compared with two other common filtering approaches (Butterworth-200Hz and CFC180 filter) through signal-to-noise ratio (SNR) and mixed linear effects models for laboratory and on-field events, respectively.Results The HEADSport filter method produced marginally higher SNR than the Butterworth-200Hz and CFC180 filter and on-field peak linear acceleration (PLA) and peak angular acceleration (PAA) values within the magnitude range tested in the laboratory. Median PLA and PAA (and outlier values) were higher for the CFC180 filter than the Butterworth-200Hz and HEADSport filter method (plt;0.01).Conclusion The HEADSport filter method could enable iMG field-based inter-study comparisons and is openly available at https://github.com/GTBiomech/HEADSport-Filter-Method.Data are available upon reasonable request. Anonymous data are available on reasonable request to the corresponding author

The Incidence and Propensity of Head Acceleration Events in a Season of Men’s and Women’s English Elite-Level Club Rugby Union Matches

Objectives: To describe and compare the incidence and propensity of head acceleration events (HAEs) using instrumented mouthguards (iMG) by playing position in a season of English elite-level men’s and women’s rugby union matches. Methods: iMG data were collected for 255 men and 133 women from 1,865 and 807 player-matches, respectively, and synchronised to video-coded match footage. Head peak resultant linear acceleration (PLA) and peak resultant angular acceleration (PAA) were extracted from each HAE. Mean incidence and propensity values were calculated across different recording thresholds for forwards and backs in addition to positional groups (front row, second row, back row, half backs, centres, back three) with 95% confidence intervals (CI) estimated. Significance was determined based on 95% CI not overlapping across recording thresholds. Results: For both men and women, HAE incidence was twice as high for forwards than backs across the majority of recording thresholds. HAE incidence and propensity were significantly lower in the women’s game compared to the men’s game. Back-row and front-row players had the highest incidence across all HAE thresholds for men’s forwards, while women’s forward positional groups and men’s and women’s back positional groups were similar. Tackles and carries exhibited a greater propensity to result in HAE for forward positional groups and the back three in the men’s game, and back row in the women’s game. Conclusion: These data offer valuable benchmark and comparative data for future research, HAE mitigation strategies, and management of HAE exposure in elite rugby players. Positional-specific differences in HAE incidence and propensity should be considered in future mitigation strategies

The Incidence of Head Acceleration Events During Pitch‐Based Training and Match Play in Professional Men's Rugby League

This study aimed to describe the incidence of head acceleration events (HAEs) during pitch‐based in‐season training and matches in professional male rugby league. Data were recorded using instrumented mouthguards from 108 players (70 forwards and 38 backs) at nine Super League teams (2024 season), resulting in 468 player‐training sessions and 665 player‐matches included. Peak linear and angular acceleration were calculated from each HAE and analyzed using generalized linear mixed‐effects models. During the 468 player‐training sessions, 814 HAEs above the lowest magnitude threshold (5 g and 400 rad.s−2) were observed and the mean HAE incidence rate per player‐hour was 1.52 (95% confidence intervals; 1.34–1.70). This was substantially lower than matches (25.78 [23.28–28.27] per player‐hour) with HAE incidence being 17 times greater during matches compared to training (incidence rate ratio 16.96 [14.92–19.01]). Higher magnitude HAEs had a lower incidence in both training and matches (e.g., &gt; 25 g 0.04 [0.02–0.06] and 2.01 [1.79–2.24] per player‐hour). Out of 468 player‐training sessions, 307 (~66%) had no HAEs &gt; 10 g and 441 (~94%) had no HAEs &gt; 25 g. Overall, the incidence rates of HAEs during training were low and substantially lower than match‐play. However, a small proportion of relatively high in magnitude HAEs do occur during training, which could be the target of prevention interventions in training. However, given the different HAE rates between training and matches, interventions targeting matches (e.g., law modifications or reduced exposure) would have a larger effect on reducing HAEs for players than training interventions

Instrumented Mouthguards in Men’s Rugby League: Quantifying the Incidence and Probability of Head Acceleration Events at a Group and Individual Level

BackgroundThere is growing concern that exposure to head acceleration events (HAEs) may be associated with long-term neurological effects.ObjectivesTo quantify the incidence and probability of HAEs during men’s professional rugby league match-play on a group and individual basis using instrumented mouthguards (iMGs).MethodsA total of 91 men’s professional rugby league players participating in the 2023 Super League season wore iMGs, resulting in the collection of 775 player matches (mean 8.3 matches per player). Incidence of HAEs (rate of HAEs per median playing time) was calculated via generalised linear mixed models. Probability of HAEs (likelihood of experiencing an HAE during a tackle-event) was calculated using an ordinal mixed effects regression model.ResultsThe mean incidence of HAEs exceeding 25 g per median playing time ranged from 0.86–1.88 for back positions and 1.83–2.02 for forward positions. The probability of exceeding 25 g during a tackle event was higher for ball-carriers (6.29%, 95% confidence intervals [CI] 5.27–7.58) than tacklers (4.26%, 95% CI 3.48–5.26). Several players exhibited considerably higher incidence and probability than others, e.g. one player averaged 5.02 HAEs exceeding 25 g per median playing time and another had a probability of 20.00% of exceeding 25 g during a tackle event as a ball-carrier and 34.78% as a tackler.ConclusionsThis study quantifies the incidence and probability of HAEs in men’s rugby league match-play, advancing our understanding of HAE exposure in men’s rugby league. These findings support the development of individualised HAE mitigation strategies targeted at individuals with elevated HAE exposures

Peak Power: A Severity Measure for Head Acceleration Events Associated with Suspected Concussions

Objectives: In elite rugby union, suspected concussions lead to immediate removal from play for either permanent exclusion or a temporary 12-min assessment as part of the Head Injury Assessment 1 (HIA1) protocol. The study aims to retrospectively identify a head acceleration event (HAE) severity measure associated with HIA1 removals in elite rugby union using instrumented mouthguards (iMGs). Methods: HAEs were recorded from 215 men and 325 women, with 30 and 28 HIA1 removals from men and women, respectively. Logistical regression was calculated to identify whether peak power, maximum principal strain (MPS) and/or the Head Acceleration Response Metric (HARM) were associated with HIA1 events compared to non-cases. Optimal threshold values were determined using the Youden Index. Area under the curve (AUC) was compared using a paired-sample approach. Significant differences were set at p &lt; 0.05. Results: All three severity measures (peak power, HARM, MPS) were associated with HIA1 removals in both the men’s and women’s game. Peak power performed most consistent of the three severity measures for HIA1 removals based on paired-sample AUC comparisons in the men’s and women’s games. The HARM and MPS were found to perform lower than peak linear acceleration in the women’s game based on AUC comparisons (p = 0.006 and 0.001, respectively), with MPS performing lower than peak angular acceleration (p = 0.001). Conclusion: Peak power, a measure based on fundamental mechanics and commonly communicated in sports performance, was the most effective metric associated with HIA1 removals in elite rugby. The study bridges the gap by identifying a consistent HAE severity measure applicable across sexes.</p