James Tooby

Instrumented mouthguards (iMG) were used to collect head acceleration events (HAE) in men's professional rugby league matches. Peak linear acceleration (PLA), peak angular acceleration (PAA) and peak change in angular velocity (ΔPAV) were collected using custom-fit iMG set with a 5 g single iMG-axis recording threshold. iMG were fitted to ten male Super League players for thirty-one player matches. Video analysis was conducted on HAE to identify the contact event; impacted player; tackle stage and head loading type. A total of 1622 video-verified HAE were recorded. Approximately three-quarters of HAE (75.7%) occurred below 10 g. Most (98.2%) HAE occurred during tackles (59.3% to tackler; 40.7% to ball carrier) and the initial collision stage of the tackle (43.9%). The initial collision stage resulted in significantly greater PAA and ΔPAV than secondary contact and play the ball tackle stages (p < 0.001). Indirect HAE accounted for 29.8% of HAE and resulted in significantly greater ΔPAV (p < 0.001) than direct HAE, but significantly lower PLA (p < 0.001). Almost all HAE were sustained in the tackle, with the majority occurring during the initial collision stage, making it an area of focus for the development of player protection strategies for both ball carriers and tacklers. League-wide and community-level implementation of iMG could enable a greater understanding of head acceleration exposure between playing positions, cohorts, and levels of play.

Objectives: To identify a head acceleration event (HAE) severity measure associated with HIA1 removals in elite level rugby union. Methods: HAEs were recorded from 215 men and 325 women with 30 and 28 HIA1 removals from men and women, respectively. Logistical regression were calculated to identify if peak power, maximum principal strain (MPS) and or 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) were compared using a paired sample approach. Significant differences were set at p<0.05. Results: All three severity measures were associated with HIA1 removals in both the mens and womens game. Power performed greatest for HIA1 removals in both the mens and womens games, based on overall AUC, sensitivity, and specificity values. HARM and MPS were found to perform lower than PLA in the womens game based on AUC comparisons (p=0.006 and 0.001, respectively), with MPS performing lower than PAA (p=0.001). Conclusion: The findings progress our understanding of HAE measures associated with HIA1 removals. Peak power, a measure based on fundamental mechanics and commonly used in sports performance, may be a suitable HAE severity measure.

ABSTRACT

The original article can be found online at https://doi.org/10.1007/s40279-023-01953-7

OBJECTIVES: The aim of this study was to examine head acceleration event (HAE) propensity and incidence during elite-level men's and women's rugby union matches. METHODS: Instrumented mouthguards (iMGs) were fitted in 92 male and 72 female players from nine elite-level clubs and three international teams. Data were collected during 406 player matches (239 male, 167 female) using iMGs and video analysis. Incidence was calculated as the number of HAEs per player hour and propensity as the proportion of contact events resulting in an HAE at a range of linear and angular thresholds. RESULTS: HAE incidence above 10 g was 22.7 and 13.2 per hour in men's forwards and backs and 11.8 and 7.2 per hour in women's forwards and backs, respectively. Propensity varied by contact event, with 35.6% and 35.4% of men's tackles and carries and 23.1% and 19.6% of women's tackles and carries producing HAEs above 1.0 krad/s2. Tackles produced significantly more HAEs than carries, and incidence was greater in forwards compared with backs for both sexes and in men compared with women. Women's forwards were 1.6 times more likely to experience a medium-magnitude HAE from a carry than women's backs. Propensity was similar from tackles and carries, and between positional groups, while significantly higher in men than women. The initial collision stage of the tackle had a higher propensity than other stages. CONCLUSION: This study quantifies HAE exposures in elite rugby union players using iMGs. Most contact events in rugby union resulted in lower-magnitude HAEs, while higher-magnitude HAEs were comparatively rare. An HAE above 40 g occurred once every 60-100 min in men and 200-300 min in women. Future research on mechanisms for HAEs may inform strategies aimed at reducing HAEs.

Objective To examine the likelihood of head acceleration events (HAEs) as a function of previously identified risk factors: match time, player status (starter or substitute) and pitch location in elite-level men’s and women’s rugby union matches. Methods Instrumented mouthguard data were collected from 179 and 107 players in the men’s and women’s games and synchronised to video-coded match footage. Head peak resultant linear acceleration (PLA) and peak resultant angular acceleration were extracted from each HAE. Field location was determined for HAEs linked to a tackle, carry or ruck. HAE incidence was calculated per player hour across PLA recording thresholds with 95% CIs estimated. Propensity was calculated as the percentage of contact events that caused HAEs across PLA recording thresholds, with a 95% CI estimated. Significance was assessed by non-overlapping 95% CIs. Results 29 099 and 6277 HAEs were collected from 1214 and 577 player-matches in the men’s and women’s games. No significant differences in match quarter HAE incidence or propensity were found. Substitutes had higher HAE incidence than starters at lower PLA recording thresholds for men but similar HAE propensity. HAEs were more likely to occur in field locations with high contact event occurrence. Conclusion Strategies to reduce HAE incidence need not consider match time or status as a substitute or starter as HAE rates are similar throughout matches, without differences in propensity between starters and substitutes. HAE incidence is proportional to contact frequency, and strategies that reduce either frequency or propensity for contact to cause head contact may be explored.

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.

Objectives The purpose of this study was to investigate head kinematic variables in elite men’s and women’s rugby union and their ability to predict player removal for an off-field (HIA1) head injury assessment. Methods Instrumented mouthguard (iMG) data were collected for 250 men and 132 women from 1865 and 807 player-matches, respectively, and synchronised to video-coded match footage. Head peak resultant linear acceleration (PLA), peak resultant angular acceleration (PAA) and peak change in angular velocity (dPAV) were extracted from each head acceleration event (HAE). HAEs were linked to documented HIA1 events, with ten logistical regression models for men and women, using a random subset of non-case HAEs, calculated to identify kinematic variables associated with HIA1 events. Receiver operating characteristic curves (ROC) were used to describe thresholds for HIA1 removal. Results Increases in PLA and dPAV were significantly associated with an increasing likelihood of HIA1 removal in the men’s game, with an OR ranging from 1.05–1.12 and 1.13–1.18, respectively. The optimal values to maximise for both sensitivity and specificity for detecting an HIA1 were 1.96 krad⋅s−2, 24.29 g and 14.75 rad⋅s−1 for PAA, PLA and dPAV, respectively. Only one model had any significant variable associated with increasing the likelihood of a HIA1 removal in the women’s game—PAA with an OR of 8.51 (1.23–58.66). The optimal values for sensitivity and specificity for women were 2.01 krad⋅s−2, 25.98 g and 15.38 rad⋅s−1 for PAA, PLA and dPAV, respectively. Conclusion PLA and dPAV were predictive of men’s HIA1 events. Further HIA1 data are needed to understand the role of head kinematic variables in the women’s game. The calculated spectrum of sensitivity and specificity of iMG alerts for HIA1 removals in men and women present a starting point for further discussion about using iMGs as an additional trigger in the existing HIA process.

Abstract

Instrumented mouthguards (iMGs) have the potential to quantify head acceleration exposures in sport. The Rugby Football League is looking to deploy iMGs to quantify head acceleration exposures as part of the Tackle and Contact Kinematics, Loads and Exposure (TaCKLE) project. iMGs and associated software platforms are novel, thus limited validation studies exist. The aim of this paper is to describe the methods that will determine the validity (ie, laboratory validation of kinematic measures and on-field validity) and feasibility (ie, player comfort and wearability and practitioner considerations) of available iMGs for quantifying head acceleration events in rugby league. Phase 1 will determine the reliability and validity of iMG kinematic measures (peak linear acceleration, peak rotational velocity, peak rotational acceleration), based on laboratory criterion standards. Players will have three-dimensional dental scans and be provided with available iMGs for phase 2 and phase 3. Phase 2 will determine the on-field validity of iMGs (ie, identifying true positive head acceleration events during a match). Phase 3 will evaluate player perceptions of fit (too loose, too tight, bulky, small/thin, held mouth open, held teeth apart, pain in jaw muscles, uneven bite), comfort (on lips, gum, tongue, teeth) and function (speech, swallowing, dry mouth). Phase 4 will evaluate the practical feasibility of iMGs, as determined by practitioners using the system usability scale (preparing iMG system and managing iMG data). The outcome will provide a systematic and robust assessment of a range of iMGs, which will help inform the suitability of each iMG system for the TaCKLE project.

Head acceleration events (HAEs) are acceleration responses of the head following external short-duration collisions. The potential risk of brain injury from a single high-magnitude HAE or repeated occurrences makes them a significant concern in sport. Instrumented mouthguards (iMGs) can approximate HAEs. The distinction between sensor acceleration events, the iMG datum for approximating HAEs and HAEs themselves, which have been defined as the in vivo event, is made to highlight limitations of approximating HAEs using iMGs. This article explores the technical limitations of iMGs that constrain the approximation of HAEs and discusses important conceptual considerations for stakeholders interpreting iMG data. The approximation of HAEs by sensor acceleration events is constrained by false positives and false negatives. False positives occur when a sensor acceleration event is recorded despite no (in vivo) HAE occurring, while false negatives occur when a sensor acceleration event is not recorded after an (in vivo) HAE has occurred. Various mechanisms contribute to false positives and false negatives. Video verification and post-processing algorithms offer effective means for eradicating most false positives, but mitigation for false negatives is less comprehensive. Consequently, current iMG research is likely to underestimate HAE exposures, especially at lower magnitudes. Future research should aim to mitigate false negatives, while current iMG datasets should be interpreted with consideration for false negatives when inferring athlete HAE exposure.

This study aimed to quantify the frequency of individual and team contact events during rugby union match play in top domestic and international men’s and women’s competitions. Analyst‐coded player individual and team contact event types (tackles, carries, attacking rucks and defensive rucks, lineouts, scrums and mauls) from the 2022/2023 rugby union season were analysed from top domestic and international competitions across the world using generalised linear mixed models. For both women’s and men’s rugby, competitions generally had similar numbers of contact events per playing position. Where differences were observed, most ranged between 0.5 and six per contact event per full game equivalent (FGE). Similar trends were observed when comparing women’s to men’s rugby. However, within‐game accumulation of these different contact events for certain positional groups may have a significant impact (e.g., a front five player called up from a Farah Palmer Cup team to play in WXV1 could be involved in as much as 6 more attacking rucks, 3 more tackles and 5 more mauls per game on average). Furthermore, the small differences between competitions per FGE may accrue across matches and thus result in far greater exposures across a season (e.g., a front five player in Premiership Rugby may make 48 more tackles over 20 matches than in Top 14 on average). Although a high proportion of contact events per FGE were similar between competitions and sexes per playing position, differences that were observed may have important implications for players transitioning between competitions and the long‐term exposure of players to higher‐risk contact events.

Objectives Assess the validity and feasibility of current instrumented mouthguards (iMGs) and associated systems. Methods Phase I; four iMG systems (Biocore-Football Research Inc (FRI), HitIQ, ORB, Prevent) were compared against dummy headform laboratory criterion standards (25, 50, 75, 100 g). Phase II; four iMG systems were evaluated for on-field validity of iMG-triggered events against video-verification to determine true-positives, false-positives and false-negatives (20±9 player matches per iMG). Phase III; four iMG systems were evaluated by 18 rugby players, for perceptions of fit, comfort and function. Phase IV; three iMG systems (Biocore-FRI, HitIQ, Prevent) were evaluated for practical feasibility (System Usability Scale (SUS)) by four practitioners. Results Phase I; total concordance correlation coefficients were 0.986, 0.965, 0.525 and 0.984 for Biocore-FRI, HitIQ, ORB and Prevent. Phase II; different on-field kinematics were observed between iMGs. Positive predictive values were 0.98, 0.90, 0.53 and 0.94 for Biocore-FRI, HitIQ, ORB and Prevent. Sensitivity values were 0.51, 0.40, 0.71 and 0.75 for Biocore-FRI, HitIQ, ORB and Prevent. Phase III; player perceptions of fit, comfort and function were 77%, 6/10, 55% for Biocore-FRI, 88%, 8/10, 61% for HitIQ, 65%, 5/10, 43% for ORB and 85%, 8/10, 67% for Prevent. Phase IV; SUS (preparation-management) was 51.3–50.6/100, 71.3–78.8/100 and 83.8–80.0/100 for Biocore-FRI, HitIQ and Prevent. Conclusion This study shows differences between current iMG systems exist. Sporting organisations can use these findings when evaluating which iMG system is most appropriate to monitor head acceleration events in athletes, supporting player welfare initiatives related to concussion and head acceleration exposure.

ABSTRACT

Objectives The aim of this study was to describe the incidence and magnitude of head acceleration events (HAEs) during elite men’s and women’s rugby union training for different contact training levels and drill types. Method Data were collected during the 2022–23 and 2023–24 seasons from 203 men and 125 women from 13 clubs using instrumented mouthguards (iMGs) during in-season training. One author reviewed the training videos to identify the contact level and drill type. HAE incidence was calculated per player minute. Results For men’s forwards and backs, only 4.7% and 5.8% of HAEs were ≥ 25 g and ≥ 1.5 Krad/s2, and 3.4% and 4.4% for women’s forwards and backs, respectively. The incidence of ≥ 5 g and ≥ 0.4 Krad/s2 was highest during full-contact training for men’s forwards (0.20/min) and backs (0.16/min) and women’s forwards (0.10/min). HAE incidence was 2–3 times higher during repetition-based compared with game-based training drills for men’s forwards (0.25/min vs 0.09/min) and backs (0.22/min vs 0.09/min) and women’s forwards (0.09/min vs 0.04/min) and backs (0.08/min vs 0.03/min). HAE incidences were halved when repetition-based training drills used pads compared with no pads for men’s forwards (0.21/min vs 0.44/min) and backs (0.17/min vs 0.30/min), and women’s forwards (0.06/min vs 0.14/min) and backs (0.06/min vs 0.10/min). Conclusion The average HAE incidence (~ 13–20% of weekly HAEs) and magnitude during an in-season training week is very low compared with matches. Opportunities to materially reduce HAE exposure in training are likely more limited than previously assumed. Future research on HAE load and injury, and understanding players’ specific weekly training exposure, may inform effective individual player management.

The study aimed to illustrate how contact (from match‐event data) and head acceleration event (HAE) (from instrumented mouthguard [iMG]) data can be combined to inform match limits within rugby. Match‐event data from one rugby union and rugby league season, including all competitive matches involving players from the English Premiership and Super League, were used. Playing exposure was summarised as full game equivalents (FGE; total minutes played/80). Expected contact and HAE exposures at arbitrary thresholds were estimated using match‐event and iMG data. Generalised linear models were used to identify differences in contact and HAE exposure per FGE. For 30 FGEs, forwards had greater contact than backs in rugby union (n = 1272 vs. 618) and league (n = 1569 vs. 706). As HAE magnitude increased, the differences between positional groups decreased (e.g., rugby union; n = 34 and 22 HAE >40 g for forwards and backs playing 30 FGEs). Currently, only a relatively small proportion of rugby union (2.5%) and league (7.3%) players exceeded 25 FGEs. Estimating contact and HAEs per FGE allows policymakers to prospectively plan and model estimated overall and position‐specific loads over a season and longer term. Reducing FGE limits by a small amount would currently only affect contact and HAE exposure for a small proportion of players who complete the most minutes. This may be beneficial for this cohort but is not an effective HAE and contact exposure reduction strategy at a population level, which requires individual player management. Given the positional differences, FGE limits should exist to manage appropriate HAE and contact exposure.

Background: There is growing concern that exposure to head acceleration events may be associated with potential long-term health consequences. Rugby league is a contact sport involving a high number of collisions, and therefore has a high risk of head accelerations. It is therefore important to quantify head acceleration exposure in rugby league. Instrumented mouthguards (iMGs) are a validated means for quantifying head acceleration events (HAEs) and have been implemented within men’s rugby league, however HAEs are yet to be quantified within women’s rugby league. Accordingly, this study implemented iMGs across teams participating in the Women’s Super League competition, with the aim of describing HAEs during matches. Methodology: Seven elite women’s rugby league teams were provided with iMGs, resulting in the collection of iMG data from 84 players, across 116 player matches. In-vivo HAEs were approximated using linear and angular kinematics measured by accelerometers and gyroscopes embedded within iMGs. Peak linear acceleration (PLA; g) and peak angular acceleration (PAA; rad/s2) were calculated to approximate the magnitude of each HAE. Validated machine learning classification algorithms were used to remove false positive events from the dataset. Results: Across 116 player matches, 1389 HAEs were recorded. The median (IQR) number of HAEs per player match was 7 (3 to 18) HAEs per player match. The median (IQR) HAE magnitude was 12 (8.6 to 18.1) g and 982 (657 to 1,723) rad/s2, for PLA and PAA, respectively. Towards the higher end of magnitudes, the 95th percentile magnitude was 36.8 g and 3,740 rad/s2. Conclusion: For the first time, HAEs have been quantified in women’s rugby league matches. Overall, the number of head accelerations per player match is lower than previously reported in men’s rugby league, while the distribution of HAE magnitudes also seems lower.

Background:Globally, sports are proactively aiming to reduce concussions and head acceleration events (HAEs) given the potential dose-response association with neurodegenerative diseases. No data exists regarding HAEs from training or commonly performed drills, which is important, as arguably the training environment is more modifiable than matches. Therefore, this study aimed to describe the HAEs during common training drills used in rugby league.Methodology:Fifteen male academy rugby league players from a professional Super League club participated. Players participated in three training sessions, with 7 standardised drills, designed in consultation with experienced coaches, completed in the same order in each session. Players wore a custom-fitted instrumented mouthguard (iMG) and each session was filmed. An iMG capture framework was developed andapplied to synchronise and process the iMG and video data to verify the HAEs occurring in a drill. The probability of a HAE being observed in a drill was estimated using binomial logistic regression and exceedance probabilities using ordinal mixed effectsregression.Results:1402 (93 ± 50 per player) drill observations were recorded, which resulted in approximately 133 observed HAEs (9 ± 8 per player). 130 HAEs were analysed further (wrestle = 48, tackler = 59, ball-carrier = 23). Standing wrestle had the highest overall probability of HAE occurrence of 41.3% (CI = 31.0 –52.3%) than the other drills (range: 0.67 –14.3%). HAE exposure was greater for tacklers than ball-carriers. Increasing the distance of the drill, e.g., tackle shield hit 1m (1.3% [0.5 –3.4]) vs 3m (9.0%[6.2 –12.8]), increased the probability of a HAE being observed. All drills were observed to have an exceedance probability of experiencing an HAE ≥25 g ~0.0% (CI = 0.0 –0.8%), except for standing wrestle 1.0% (CI = 0.2 -4.1%).Conclusion:For the first time the findings from this study offer insights into HAE exposure from various common training drills in rugby league. While the overall chance of high-magnitude HAEs was relatively low, the contextual and constraint-based variability in HAE exposure between drills demonstrates the need for practitioners to consider how manipulating constraints may affect HAE exposure and accumulation.

The aim of this study was to investigate the difference in head acceleration event (HAE) incidence between training and match‐play in women's and men's players competing at the highest level of domestic rugby union globally. Players from Women's (Premiership Women's Rugby, Farah Palmer Cup) and Men's (Premiership Rugby, Currie Cup) rugby union competitions wore instrumented mouthguards during matches and training sessions during the 2022/2023 seasons. Peak linear (PLA) and angular (PAA) acceleration were calculated from each HAE and included within generalized linear mixed‐effects models. The incidence of HAEs was significantly greater in match‐play compared to training for all magnitude thresholds in both forwards and backs, despite players spending approximately 1.75–2.5 times more time in training. For all HAEs (PLA > 5 g and PAA > 400 rad/s2), incidence rate ratios (IRRs) for match versus training ranged from 2.80 (95% CI: 2.38–3.30; men's forwards) to 4.00 (3.31–4.84; women's forwards). At higher magnitude thresholds (PLA > 25 g; PAA > 2000 rad/s2), IRRs ranged from 3.64 (2.02–6.55; PAA > 2000 rad/s2 in men's backs) to 11.70 (6.50–21.08; PAA > 2000 rad/s2 in women's forwards). Similar trends were observed in each competition. Players experienced significantly more HAEs during match‐play than training, particularly at higher magnitude thresholds. Where feasible, HAE mitigation strategies may have more scope for HAE reduction if targeted at match‐play, particularly where higher magnitude HAEs are the primary concern. However, the number of HAEs associated with different training drills requires exploration to understand if HAEs can be reduced in training, alongside optimizing match performance (e.g., enhancing contact technique).

This study aimed to quantify and compare mean head acceleration event (HAE) incidence within and between men's and women's rugby union competitions; quantify the incidence of HAEs during all contact‐events and describe individual player incidence. Players competing during the 2022/2023 season in women's (337 players; Premiership Women's Rugby, Farah Palmer Cup) and men's (371 players; Premiership Rugby, Currie Cup and Super Rugby) competitions wore instrumented mouthguards (iMGs). Mean HAE incidences using peak linear (PLA) and peak angular acceleration (PAA) were quantified by sex, positional groups and individual players per competition and for contact‐events across a range of magnitude thresholds. Within positional groups, there was high between‐player variability, with some players experiencing up to a 3‐fold greater mean HAE incidence than their positional average. Per full‐game equivalent (FGE), men had significantly higher HAE incidences in most positional groups and HAE magnitude thresholds compared to women ranging from approximately 0.11–3.44 HAEs per FGE. Incidence of HAEs (PLA > 25 g) per FGE was lowest in scrums (0.00–0.04/FGE) and highest for tackles and ball carries (0.21–1.97/FGE) in both women and men, whereas mauling was a frequent source of HAEs for men's back row (0.95/FGE). No significant differences were observed between competitions for most positional groups and HAE magnitude thresholds in both men and women. Per FGE, HAE incidences were similar within, but significant differences were apparent between men's and women's players. The scrum had the lowest HAE incidence of all contact‐events. Individual players can show large variation from the mean, emphasising the importance of HAE mitigation strategies that include individual player monitoring and management processes.

Background Head acceleration events (HAEs) are an increasing concern in collision sports owing to potential negative health outcomes. Objectives The objective of this study is to describe the probabilities of HAEs in tackles of differing heights and body positions in elite men’s and women’s rugby union. Methods Instrumented mouthguards (iMGs) were worn in men’s (n = 24 teams, 508 players, 782 observations) and women’s (n = 26 teams, 350 players, 1080 observations) rugby union matches. Tackle height (i.e. point of contact on ball-carrier) and body positions of tacklers and ball-carriers were labelled for all tackles in which a player wore an iMG. HAEs from the initial impact were identified. Mean player, tackler and ball-carrier exceedance probabilities for various peak linear and angular acceleration thresholds were estimated from ordinal mixed-effects models. Results Contact with ball-carriers’ head/neck resulted in the highest mean HAE probabilities for both sexes. The probability of an HAE to the ball-carrier decreased as tackle height lowered. The highest probability for the tackler was initial contact to the ball-carriers upper leg. Body position influenced the probability of HAEs, with falling/diving ball-carriers resulting in higher mean probabilities. When a player, regardless of role, was bent-at-waist, elevated HAE probabilities were observed in men’s competitions. Women’s data demonstrated similar probabilities of an HAE for all body positions. Conclusions Initial contact to the ball-carrier’s head/neck had the highest chance of an HAE, whilst role-specific differences are apparent for different tackle heights and body positions. Future player-welfare strategies targeting contact events should therefore consider HAE mechanisms along with current literature.

The original article has been updated to add the missing Electronic Supplemental Material.

Purpose Head acceleration events (HAEs) are a growing concern in contact sports, prompting two rugby governing bodies to mandate instrumented mouthguards (iMGs). This has resulted in an influx of data imposing financial and time constraints. This study presents two computational methods that leverage a dataset of video-coded match events: cross-correlation synchronisation aligns iMG data to a video recording, by providing playback timestamps for each HAE, enabling analysts to locate them in video footage; and post-synchronisation event matching identifies the coded match event (e.g. tackles and ball carries) from a video analysis dataset for each HAE, this process is important for calculating the probability of match events resulting in HAEs. Given the professional context of iMGs in rugby, utilising commercial sources of coded match event datasets may expedite iMG analysis. Methods Accuracy and validity of the methods were assessed via video verification during 60 rugby matches. The accuracy of cross-correlation synchronisation was determined by calculating synchronisation error, whilst the validity of post-synchronisation event matching was evaluated using diagnostic accuracy measures (e.g. positive predictive value [PPV] and sensitivity). Results Cross-correlation synchronisation yielded mean synchronisation errors of 0.61–0.71 s, with all matches synchronised within 3 s’ error. Post-synchronisation event matching achieved PPVs of 0.90–0.95 and sensitivity of 0.99–1.00 for identifying correct match events for SAEs. Conclusion Both methods achieved high accuracy and validity with the data sources used in this study. Implementation depends on the availability of a dataset of video-coded match events; however, integrating commercially available video-coded datasets offers the potential to expedite iMG analysis, improve feedback timeliness, and augment research analysis.

This study aimed to quantify contact-events and associated head acceleration event (HAE) probabilities in semi-elite women's rugby union. Instrumented mouthguards (iMGs) were worn by players competing in the 2023 Farah Palmer Cup season (13 teams, 217 players) during 441 player-matches. Maximum peak linear acceleration (PLA) and peak angular acceleration (PAA) per-event were used as estimates of in vivo HAE (HAEmax), linked to video analysis-derived contact-events and analysed using mixed-effects regression. Back-rows had the highest number of contact-events per full-match (44.1 [41.2 to 47.1]). No differences were apparent between front-five and centres, or between half-backs and outside-backs. The probability of higher HAEmax occurring was greatest in ball-carries, followed by tackles, defensive rucks and attacking rucks. Probability profiles were similar between positions but the difference in contact-events for each position influenced HAEmax exposure. Overall, most HAEmax were relatively low. For example, the probability of a back-row experiencing a PLA HAEmax ≥25g was 0.045 (0.037-0.054) for ball carries (1 in every 22 carries), translating to 1 in every 2.3 full games. This study presents the first in-depth analysis of contact-events and associated HAEmax in semi-elite women's rugby union. The HAEmax profiles during contact-events can help inform both policy and research into injury mitigation strategies.

Instrumented mouthguards (iMGs) are a novel technology being used within rugby to quantify head acceleration events. Understanding practitioners' perceptions of the barriers and facilitators to their use is important to support implementation and adoption. This study assessed men's and women's rugby union and league iMG managers' perceptions of staff and player interest in the technology, data and barriers to use. Forty‐six iMG managers (men's rugby union and league n = 20 and n = 9 and women's rugby union and league n = 7 and n = 10) completed an 18‐question survey. Perceived interest in data varied across staff roles with medical staff being reported as having the most interest. The iMG devices were perceived as easy to use but uncomfortable. Several uses of data were identified, including medical applications, player monitoring and player welfare. The comfort, size and fit of the iMG were reported as the major barriers to player use. Time constraints and a lack of understanding of data were barriers to engagement with the data. Continued education on how iMG data can be used is required to increase player and staff buy‐in, alongside improving comfort of the devices. Studies undertaken with iMGs investigating player performance and welfare outcomes will make data more useful and increase engagement.

Objectives Describe head acceleration events (HAEs) experienced by professional male rugby union players during tackle, ball‐carry, and ruck events using instrumented mouthguards (iMGs). Design Prospective observational cohort. Methods Players competing in the 2023 Currie Cup (141 players) and Super Rugby (66 players) seasons wore iMGs. The iMG‐recorded peak linear acceleration (PLA) and peak angular acceleration (PAA) were used as in vivo HAE approximations and linked to contact‐event data captured using video analysis. Using the maximum PLA and PAA per contact event (HAEmax), ordinal mixed‐effects regression models estimated the probabilities of HAEmax magnitude ranges occurring, while accounting for the multilevel data structure. Results As HAEmax magnitude increased the probability of occurrence decreased. The probability of a HAEmax ≥15g was 0.461 (0.435–0.488) (approximately 1 in every 2) and ≥45g was 0.031 (0.025–0.037) (1 in every 32) during ball carries. The probability of a HAEmax >15g was 0.381 (0.360–0.404) (1 in every 3) and >45g 0.019 (0.015–0.023) (1 in every 53) during tackles. The probability of higher magnitude HAEmax occurring was greatest during ball carries, followed by tackles, defensive rucks and attacking rucks, with some ruck types having similar profiles to tackles and ball carries. No clear differences between positions were observed. Conclusion Higher magnitude HAEmax were relatively infrequent in professional men's rugby union players. Contact events appear different, but no differences were found between positions. The occurrence of HAEmax was associated with roles players performed within contact events, not their actual playing position. Defending rucks may warrant greater consideration in injury prevention research.

Background: Head acceleration events (HAEs) are a source of concern across sport due to potential negative long-term brain health in athletes exposed to them. Tackle height is highlighted as a possible factor for risk mitigation in rugby codes. This study aimed to identify the probability of the ball-carrier and tackler receiving a HAE for a given tackle height and estimate the potential impact of changes in tackle height. Methodology: A prospective observational cohort study was conducted during the men’s elite rugby league Super League 2023 season (12 teams, 94 players, 702 player matches). HAEs recorded from instrumented mouthguards were linked to ball-carries and tackles confirmed via video. Events were then labelled by tackle height (i.e., contact on ball-carrier; head/neck, shoulder, upper torso, abdomen, shorts, upper leg and lower leg). Only initial collision HAEs were analysed. Ordinal mixed-effects regression models provided exceedance probabilities for peak linear acceleration (recorded, >10g, >25g, >40g, >55g and >70g) and peak angular acceleration (recorded, >1000rads/s2, >2000 rads/s2, >3000 rads/s2, >4000 rads/s2, and >5000 rads/s2). Differences in initial HAEs were simulated across a range of tackle height distributions using the probabilities and the total number of tackles across the season. Results: The probability of a ball-carrier and tackler recording an initial HAE were 13.4% and 24.2%. The greatest exceedance probabilities for the ball-carrier were initial impact to the head/neck: 35.5% recorded, 4.0% >25g, 13.6% >2000 rads/s2. For other impact locations, ball-carrier HAE probability was 20% at all tackle heights except impact to the ball-carriers head/neck (12.2%). The highest probability for the tackler was contact with the shorts (recorded; 30.9%, >25g; 3.0%, >2000 rads/s2; 11.7%). When 40% of tackles were redistributed from the shoulder to lower parts of the body evenly, the estimated number of HAEs reduced from 40,292 to 35,358. Conclusion: The probability of receiving a HAE for the tackler and ball-carrier differs by overall probability and tackle height. Consequently, simulating the redistribution of tackles below the line of the shoulder suggests there could be a lower number of initial HAE observed across a season.

Background:In collision sports, like rugby union, there is a growing interest in the long-term effects of head acceleration events (HAEs) on brain health. Current methods for understanding HAE exposure have focused on using “inferential variability” as opposed to “outcome variability”. This study aims to use simulation to evaluate outcome variability and provide expected HAE reference ranges in men’s and women’s rugby union across a micro-(weekly), meso-(monthly) and macro-(annual) cycle.Methodology:A prospective observational study was conducted in rugby union players from two professional men’s and two semi-professional women’s competitions. A total of 982 players were included across 132 training weeks and 365 matches. Generalised linear mixed models were used to estimate the count of HAEs, HAEs >25g and >2,000 rads/s2 across training contact types and match-play. Simulations of model estimates, accounting for player and weekly variation, were used to provide reference ranges of expected HAE counts, using current world rugby contact guidelines. Meso-cycles were simulated for players in three categories; high (30 matches), moderate (20 matches) and low (10 matches) match exposure.Results:For both sexes within a micro-and meso-cycle, the reference ranges between positions overlap despite differences in the median expected HAE exposures (e.g., >25g HAEs: male forwards 4 [0-10] vs. male backs 2 [0-8]). Where differences are present, forwards have greater expected HAE counts and variation (indicated by a wider distribution). Meso-cycles simulations identified a clear differentiation in distributions of expected HAEs between all match exposure levels. Generally, more matches playedresulted in higher reference ranges of HAEs, but some low match exposure simulations had a higher HAE count than some high match exposure simulations.Conclusion:The results show wide variability in “normal” weekly, monthly and annual HAE exposures. These reference ranges can be used by practitioners to identify individual players that are exposed to a large number of HAEs and serve as a baseline for future policy change regarding match and training exposure limits.

Background There is growing concern that exposure to head acceleration events (HAEs) may be associated with long-term neurological effects. Objectives To 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). Methods A 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. Results The 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. Conclusions This 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.

Objective: To quantify concussion and head acceleration event (HAE) probability in rugby league tackles by tackle-height and role and simulate seasonal counts across different tackle-height distributions. Methods: Using a prospective cohort study, data reflecting clinically diagnosed concussions (n=56) and HAEs (n=4,632; measured via instrumented mouthguards from 23,081 tackles in 92 players) were collected during the 2023 men’s Super League season. Video analysis captured tackle-heights for all concussive and accelerometer-measured tackles. Role-specific probabilities were calculated using cumulative link mixed models. Monte Carlo simulation quantified concussions and HAEs across the current tackle-height distribution, and three lower tackle-height distributions (weighted redistribution [increased torso tackles], even redistribution [increased torso and lower body tackles] and observed law trial distribution). Results: Ball-carriers experienced the highest concussion and HAE risk from head/neck contact compared to other tackle-heights (e.g., HAE ≥25g; 2.7% vs 0.4-1.1%), whilst tackler risk was similar. The number of ball-carrier concussions (16 vs 8-9) and HAEs (≥25g; 830 vs 357-556) decreased with all lower tackle-height distributions. For tacklers, the only meaningful change was an increase in HAEs following the even redistribution of a lower tackle-height (≥25g; 2081 vs 2204). When considering both roles together, only even and weighted lower tackle-height redistributions reduced the total number of lower-to-moderate magnitude HAEs, with no meaningful differences observed for concussions or higher magnitude (≥55g) HAEs. Conclusion: Lowering the tackle-height creates a protection paradox, benefiting ball-carriers, whilst potentially maintaining or increasing the risk for tacklers. Simulated findings may inform policy changes by estimating outcomes and allowing evaluation prior to implementation.

Background This study simulated the effect of reducing contact training duration on overall in-season head acceleration event (HAE) exposure within men’s and women’s rugby union. Methods Players (n = 982) from two professional men’s and two semi-professional women’s competitions wore instrumented mouthguards in training and match-play for one season. Generalised linear mixed models were used to estimate the in-season weekly HAE exposures per position, sex and contact type. Simulation of modelled estimates evaluated the impact of reducing contact load guidelines by 25%, 50% and 75% (scenario 1), and replacing full contact training with controlled contact (scenario 2) or non-contact (scenario 3) training for different seasonal match exposures. Previously established contact load guidelines were used as a reference point. Results HAEs were decreased by a maximum of 3.2 per week (0–95 HAEs per season; 0–23%). In scenario 1, the decrease in HAEs was disproportionately smaller than the reduction in contact training duration (e.g. 23.7% reduction in overall rugby minutes for 7% decrease in HAEs). Scenario 2 decreased HAEs similarly to scenario 1 but with no reduction in contact time. Scenario 3 decreased HAEs proportionally with contact time reductions (e.g. 8.9% decrease in HAEs >10 g for 9.6% reduction in overall rugby minutes). Conclusions HAEs were reduced in all scenarios, but the reduction was relatively small due to the low overall rate of HAEs in training. Policymakers should be aware of the tradeoffs involved in any change. Managing individuals with higher HAE exposures may be more appropriate than reducing contact training guidelines.

Background Head acceleration event (HAE) exposure is a concern in sport owing to potential effects on brain health. Despite growth in the sport's growing in popularity, HAE exposure in women’s rugby league has yet to be quantified. Objectives The aim of the study was to examine HAE incidence and probability across Women’s Super League rugby league players, including position- and player-specific HAE incidence and probability. Methods Instrumented mouthguards (iMGs) were worn by 136 players during the 2024 season, across 48 video-analysed matches, resulting in 568 player matches with iMG data. The incidence of HAEs and the probability of HAEs from ball-carries and tackle attempts were estimated using generalised linear mixed models and average positions on an individual-player basis. Results The average incidence of HAEs exceeding 25 g ranged from 0.40 to 0.65 per median playing time for back positions and 0.54 to 0.66 for forward positions. The probability of recording an HAE exceeding 25 g during a ball-carry was 1.33% and a tackle-attempt was 1.28%. Some individuals had higher HAE incidence and probability compared with position group means (e.g. one player exhibited an average of 1.77 HAEs exceeding 25 g per match, over double the average for their position). Conclusions This study quantifies HAE incidence and probability in women’s rugby league match-play, allowing for the comparison of HAE exposure with other sports. Overall, HAE incidence is lower than previously reported for men’s rugby league and for women’s rugby union. However, given elevated HAE incidence in some players, continued HAE monitoring using iMGs is necessary for managing the potential risks of HAE exposure.

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., > 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 > 10 g and 441 (~94%) had no HAEs > 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.