Tacklers' shoulder abduction and flexion at contact alter when engaging in different front-on, one-on-one tackle instructions from an expert coach.

OBJECTIVES: To ascertain how the three-dimensional shoulder kinematics of tacklers alter when performing four legal types of front-on, one-on-one, rugby-style torso tackles. DESIGN: Controlled laboratory study. METHODS: Three-dimensional motion capture measured 15 male amateur-level rugby code players (24.3±6.1 years) who were instructed by an expert coach to perform four sets of 10 front-on, one-on-one tackles. Four sets comprised two smother and two dominant tackles: two based on the Australian National Rugby League coaching manual (Dominant NRL, Smother NRL); and two modifications via increasing the contact height from the lower- to mid-torso (Dominant, Torso Stick) or from the upper- to mid-upper torso with a vertical 'pop action' that changes the way the tackler contacted the ball carrier's upper torso (Smother, Pop, Lock). Mixed general linear models were applied. RESULTS: Greater shoulder abduction, flexion and internal rotation were displayed by the DNRL tackle technique than in any other technique (p<0.001). At contact, the Smother and Dominant NRL (p<0.03) showed greater head-uptrunk contralateral rotation away from the tackle than the Smother, Pop, Lock. CONCLUSIONS: Tacklers modified the way they positioned their shoulder joint when engaging in legal front-on, one-on-one tackles with different tackle instructions. More prominent positions of shoulder abduction and flexion, and head-uptrunk contralateral rotation were observed when executing the traditional tackle techniques (Smother NRL, Dominant NRL) as opposed to two variants of these (Smother, Pop, Lock, Dominant, Torso Stick). Inclusion of tackle specific coaching instructions provides emerging scientific evidence to support revised coaching tackling technique interventions that might enhance player safety.

Tackle Risk Factors for Head Injury Assessments (HIAs) in Sub-Elite Rugby League and Recommendations for Prevention: Head Contacts from Upright Tackles Increase the HIA Risk to Both Ball Carrier and Tackler.

BACKGROUND: The rugby league tackle has been identified as the game event with the greatest propensity for a clinically diagnosed concussion. This study aims to replicate the work conducted in professional rugby league and rugby union by examining Head Injury Assessment (HIA) events to determine the associated tackle characteristics that increase concussion risk in sub-elite rugby league players. This comparison between competition levels is important due to the less developed physiological and tackle proficiency characteristics of sub-elite rugby league players and the fewer resources available for an on-field diagnosis, compared to the elite level of the sport. RESULTS: Tackles resulting in Head Injury Assessments (HIAs, n = 131) and 2,088 tackles that did not result in a head injury were identified and coded from one season of the 2019 Queensland Cup. The body position of both ball carrier and tackler, tackle height, and body contact areas were evaluated. The propensity for tacklers to undergo a head injury assessment was 1.49 HIAs per 1,000 tackles, equating to a 2.5-fold higher risk than that of the ball carrier (0.59 HIAs per 1,000 tackles). The risk for an HIA was 2.75-fold greater when the tackler was upright (2.89 HIAs per 1,000 tackles) compared to a bent-at-the-waist tackler (1.05 HIAs per 1,000 tackles). The greatest risk for the tackler and ball carrier sustaining an HIA occurred when the tackle height was high, with head-to-head contact having the greatest propensity for an HIA (44.37 HIAs per 1,000 tackles). HIA risk was also greater for both players when the ball carrier did not employ an evasion strategy (3.73 HIAs per 1,000 tackles). CONCLUSIONS: The study replicates results from research in elite rugby league and rugby union. A combination of higher head contact/proximity and upright body position significantly increase an HIA risk. Tackler head position and ball carrier evasion behaviours also affect risk, suggesting that injury prevention strategies designed to reduce tackle height and improve tackle technique by focusing on head position, body position, and in a novel finding, ball carrier evasion, may reduce head injury risk in sub-elite rugby league players.

Applying the Consensus Criteria for Traumatic Encephalopathy Syndrome Retrospectively to Case Studies of Boxers from the 20th Century.

There are no validated diagnostic criteria for traumatic encephalopathy syndrome (TES). During the early and middle 20th century, TES was described as a clinical condition that was experienced by some high-exposure boxers-and it was believed to reflect chronic traumatic brain injury. Consensus criteria for the diagnosis of TES were published in 2021. We applied the consensus criteria for TES retrospectively to cases of chronic brain damage in boxers described in articles published in the 20th century that were obtained from narrative and systematic reviews. The sample included 157 boxers identified in 21 articles published between 1929 and 1999. Two authors reviewed each case description and coded the criteria for TES. For the core clinical features, cognitive impairment was noted in 63.1%, and in 28.7% of cases the person's cognitive functioning appeared to be broadly normal. Neurobehavioral dysregulation was present in 25.5%. One third (34.4%) were identified as progressive, 30.6% were not progressive, and the course could not be clearly determined in 35.0%. In total, 29.9% met the TES consensus criteria, 28.0% did not, and 42.0% had insufficient information to make a diagnostic determination. TES, in the 20th century, was described as a neurological condition, not a psychiatric disorder-and this supports the decision of the 2021 consensus group to remove primary and secondary psychiatric diagnoses from being a core diagnostic feature. Future research is needed to determine whether, or the extent to which, cognitive impairment or neurobehavioral dysregulation described as characterizing TES are associated with chronic traumatic encephalopathy neuropathological change.

Chronic traumatic encephalopathy neuropathologic change in former Australian rugby players.

AIMS: We applied the 2021 consensus criteria for both chronic traumatic encephalopathy neuropathological change and traumatic encephalopathy syndrome in a small case series of six former elite-level Australian rugby code players. METHODS: Neuropathological assessment of these cases was carried out at the Sydney and Victorian Brain Banks. Clinical data were collected via clinical interviews and health questionnaires completed by the participants and/or their next of kin, and neuropsychological testing was conducted with participants who were capable of completing this testing. RESULTS: All cases exhibited progressive cognitive impairment during life. Chronic traumatic encephalopathy neuropathological change was identified in four out of the six cases. However, coexisting neuropathologies were common, with limbic-predominant age-related TDP-43 encephalopathy and ageing-related tau astrogliopathy seen in all cases, intermediate or high Alzheimer's disease neuropathological change seen in four cases and hippocampal sclerosis seen in two of the six cases. CONCLUSION: The presence of multiple neuropathologies in these cases complicates clinical diagnostic efforts for traumatic encephalopathy syndrome. It will be important for further clinicopathological studies on larger groups to report all neuropathological comorbidities found in cases diagnosed with either chronic traumatic encephalopathy neuropathological change and/or traumatic encephalopathy syndrome.

Validation of an instrumented mouthguard in rugby union-a pilot study comparing impact sensor technology to video analysis.

Background: To better understand the biomechanical profile of direct head impacts and the game scenarios in which they occur in Rugby Union, there is a need for an on-field validation of a new instrumented mouthguard (IMG) against the reference standard. This study considers the potential of a combined biomechanical (IMG) and video analysis approach to direct head impact recognition, both of which in isolation have limitations. The aim of this study is to assess the relationship between an instrumented mouthguard and video analysis in detection of direct head impacts in rugby union. Design: Pilot Study - Observational Cohort design. Methods: The instrumented mouthguard was worn by ten (3 backs, 7 forwards) professional Rugby Union players during the 2020-21 Gallagher Premiership (UK) season. Game-day video was synchronized with timestamped head acceleration events captured from the instrumented mouthguard. Direct Head Impacts were recorded in a 2 × 2 contingency table to determine sensitivity. Impact characteristics were also collected for all verified head impacts to further the understanding of head biomechanics during the game. Results: There were 2018 contact events that were reviewed using video analysis. Of those 655 were categorized as direct head impacts which also correlated with a head acceleration event captured by the IMG. Sensitivity analysis showed an overall sensitivity of 93.6% and a positive predictive value (PPV of 92.4%). When false positives were excluded due to ball out of play, mouthguard removal or handling after a scoring situation or stoppage, PPV was improved (98.3%). Most verified head impacts occurred in and around the ruck contest (31.2%) followed by impacts to the primary tackler (28.4%). Conclusion: This pilot validation study demonstrates that this IMG provides a highly accurate measurement device that could be used to complement video verification in the recognition of on-field direct head impacts. The frequency and magnitude of direct head impacts derived from specific game scenarios has been described and allows for greater recognition of high-risk situations. Further studies with larger sample sizes and in different populations of Rugby Union players are required to develop our understanding of head impact and enable strategies for injury mitigation.

Incidence of concussion in men's Super League, Championship, and Academy rugby league matches between 2016 and 2022.

OBJECTIVES: To quantify the incidence of concussion and compare between playing levels in male rugby league. DESIGN: Retrospective cohort. METHODS: Between 2016 and 2022, medically diagnosed concussions in Super League, Championship, and Academy competitions were reported to the Rugby Football League via club medical staff. Anonymised data were analysed using generalised linear mixed-effects models by season, month, and between competitions. RESULTS: Overall, 1403 concussions were identified from 104,209 player-match hours. Concussion incidence for Super League, Championship, and Academy was 15.5, 10.5, and 14.3 per 1000 player-match hours, respectively. Championship concussion incidence was significantly lower than the Super League (p < 0.001) and Academy (p < 0.001). No significant differences were identified between years for Super League (range: 13.3 to 18.8 per 1000 player-match hours) and Championship (range: 8.4 to 12.1 per 1000 player-match hours). In Academy (range: 9.6 to 20.5 per 1000 player-match hours), concussion incidence was significantly greater in 2021 compared to earlier years (2016, p = 0.01 and 2017, p = 0.03). No significant differences were identified between months for any competition. CONCLUSIONS: The incidence of concussion is greater in Super League and Academy compared to the Championship. Academy concussion incidence has increased over time. Different factors between and within competitions, such as changes to medical standards and knowledge, could have influenced the identification and diagnosis of concussion.

A narrative review of psychiatric features of traumatic encephalopathy syndrome as conceptualized in the 20th century.

Introduction: Some ultra-high exposure boxers from the 20th century suffered from neurological problems characterized by slurred speech, personality changes (e.g., childishness or aggressiveness), and frank gait and coordination problems, with some noted to have progressive Parkinsonian-like signs. Varying degrees of cognitive impairment were also described, with some experiencing moderate to severe dementia. The onset of the neurological problems often began while they were young men and still actively fighting. More recently, traumatic encephalopathy syndrome (TES) has been proposed to be present in athletes who have a history of contact (e.g., soccer) and collision sport participation (e.g., American-style football). The characterization of TES has incorporated a much broader description than the neurological problems described in boxers from the 20th century. Some have considered TES to include depression, suicidality, anxiety, and substance abuse. Purpose: We carefully re-examined the published clinical literature of boxing cases from the 20th century to determine whether there is evidence to support conceptualizing psychiatric problems as being diagnostic clinical features of TES. Methods: We reviewed clinical descriptions from 155 current and former boxers described in 21 articles published between 1928 and 1999. Results: More than one third of cases (34.8%) had a psychiatric, neuropsychiatric, or neurobehavioral problem described in their case histories. However, only 6.5% of the cases were described as primarily psychiatric or neuropsychiatric in nature. The percentages documented as having specific psychiatric problems were as follows: depression = 11.0%, suicidality = 0.6%, anxiety = 3.9%, anger control problems = 20.0%, paranoia/suspiciousness = 11.6%, and personality change = 25.2%. Discussion: We conclude that depression, suicidality (i.e., suicidal ideation, intent, or planning), and anxiety were not considered to be clinical features of TES during the 20th century. The present review supports the decision of the consensus group to remove mood and anxiety disorders, and suicidality, from the new 2021 consensus core diagnostic criteria for TES. More research is needed to determine if anger dyscontrol is a core feature of TES with a clear clinicopathological association. The present findings, combined with a recently published large clinicopathological association study, suggest that mood and anxiety disorders are not characteristic of TES and they are not associated with chronic traumatic encephalopathy neuropathologic change.

A case-control study of tackle based head impact event (HIE) risk factors from the first three seasons of the National Rugby League Women's competition.

Objective: The tackle is the most injurious event in rugby league and carries the greatest risk of concussion. This study aims to replicate previous research conducted in professional men's rugby league by examining the association between selected tackle characteristics and head impact events (HIEs) in women's professional rugby league. Methods: We reviewed and coded 83 tackles resulting in an HIE and every tackle (6,318 tackles) that did not result in an HIE for three seasons (2018-2020) of the National Rugby League Women's (NRLW) competition. Tackle height, body position of the tackler and ball carrier, as well as the location of head contact with the other player's body were evaluated. Propensity of each situation that caused an HIE was calculated as HIEs per 1,000 tackles. Results: The propensity for tacklers to sustain an HIE was 6.60 per 1,000 tackles (95% CI: 4.87-8.92), similar to that of the ball carrier (6.13 per 1,000 tackles, 95% CI: 4.48-8.38). The greatest risk of an HIE to either the tackler or ball carrier occurred when head proximity was above the sternum (21.66 per 1,000 tackles, 95% CI: 16.55-28.35). HIEs were most common following impacts between two heads (287.23 HIEs per 1,000 tackles, 95% CI: 196.98-418.84). The lowest propensity for both tackler (2.65 per 1,000 tackles, 95% CI: 0.85-8.20) and ball carrier HIEs (1.77 per 1,000 tackles, 95% CI: 0.44-7.06) occurred when the head was in proximity to the opponent's shoulder and arm. No body position (upright, bent or unbalanced/off feet) was associated with an increased propensity of HIE to either tackler or ball carrier. Conclusions: In the NRLW competition, tacklers and ball carriers have a similar risk of sustaining an HIE during a tackle, differing from men's NRL players, where tacklers have a higher risk of HIEs. Further studies involving larger samples need to validate these findings. However, our results indicate that injury prevention initiatives in women's rugby league should focus on how the ball carrier engages in contact during the tackle as well as how the tackler executes the tackle.

The propensity of non-concussive and concussive head contacts during elite-level women's rugby league matches: A prospective analysis of over 14,000 tackle events.

OBJECTIVES: Identify the frequency, propensity, and factors related to tackle events which result in contact with the head in elite-level women's rugby league. DESIGN: Prospective video analysis study. METHODS: Video footage from 59 Women's Super League matches were analysed (n = 14,378 tackle events). All tackle events were coded as no head contact or head contact. Other independent variables included: area contacting head, impacted player, concussion outcome, penalty outcome, round of competition, time in match and team standard. RESULTS: There were 83.0 ±â€¯20.0 (propensity 304.0/1000 tackle events) head contacts per match. The propensity of head contact was significantly greater for the tackler than ball-carrier (178.5 vs. 125.7/1000 tackle events; incident rate ratio 1.42, 95 % confidence interval 1.34 to 1.50). Head contacts occurring from an arm, shoulder, and head occurred significantly more than any other contact type. The propensity of concussions was 2.7/1000 head contacts. There was no significant influence of team standard or time in match on the propensity of head contacts. CONCLUSIONS: The observed head contacts can inform interventions, primarily focusing on the tackler not contacting the ball-carrier's head. The tackler's head should also be appropriately positioned to avoid contact with the ball-carrier's knee (highest propensity for concussion). The findings are consistent with other research in men's rugby. Law modifications and/or enforcement (reducing the number of un-penalised head contacts), concurrent with coaching interventions (optimising head placement or reducing the head being contacted) may help minimise head contact risk factors for women's rugby league.

Examining Whether Loss of Consciousness Is Associated With Worse Performance on the SCAT5 and Slower Clinical Recovery After Concussion in Professional Athletes.

Video surveillance has almost universally been employed by professional sports to identify signs of concussion during competition. This study examined associations between video-identified possible loss of consciousness (LOC), acute concussion evaluation findings, and recovery time in concussed professional rugby league players. Medical personnel and sideline video operators identified head impact events sustained during three seasons of National Rugby League (NRL) matches to determine the need for further medical evaluation. If a concussion was suspected, players were removed from play and underwent a Head Injury Assessment, including the Sports Concussion Assessment Tool, Fifth Edition (SCAT5). Video footage was later examined to identify signs of possible LOC (i.e., observed LOC, no protective action in the fall, and unresponsiveness or lying motionless). Possible LOC was identified in 99 of the 1706 head impact events (5.8%). The median duration of apparent unresponsiveness was 4.2 sec (M = 7.4, standard deviation [SD] = 12.8, interquartile range [IQR] = 2.5-6.6). In the 661 athletes for whom SCAT5 data were available, those with possible LOC endorsed more SCAT5 symptoms and performed worse on Maddocks questions, Standardized Assessment of Concussion (SAC) total scores, orientation, immediate recall, concentration, and delayed recall. For the 255 players with medically diagnosed concussions, SCAT5 data were available for 245. Concussed players with possible LOC performed significantly worse on Maddocks questions. However, there were no group differences in SCAT5 symptom endorsement, SAC total scores, orientation, immediate recall, concentration, delayed recall, or the modified version of the Balance Error Scoring System (mBESS) total errors. Further, the presence or absence of possible LOC was not associated with number of games missed or time to medical clearance for match play. The duration of possible LOC was not associated with the number of games missed or time to medical clearance for match play. According to video review in NRL players, brief LOC might be more common than previously thought. The present study reveals possible LOC is not predictive of missed games or time to recover following concussion.

Prevalence of chronic traumatic encephalopathy in the Sydney Brain Bank.

Chronic traumatic encephalopathy neuropathologic change can only be definitively diagnosed post-mortem. It has been associated with repetitive mild neurotrauma sustained in amateur and professional contact, collision and combat sports, although it has also been documented in people with a single severe traumatic brain injury and in some people with no known history of brain injury. The characteristic neuropathology is an accumulation of perivascular neuronal and astrocytic phosphorylated tau in the depths of the cortical sulci. The tau-immunopositive neurons and astrocytes that are considered pathognomonic for chronic traumatic encephalopathy are morphologically indistinguishable from Alzheimer-related neurofibrillary tangles and ageing-related tau astrogliopathy, respectively, although they are found in different spatial distributions throughout the cortex. The Sydney Brain Bank collection consists of neurodegenerative diseases and neurologically normal controls. We screened 636 of these cases for chronic traumatic encephalopathy neuropathologic change. A subset of 109 cases had a known history of traumatic brain injury. Three cortical regions were screened for the presence of neuronal and astrocytic phosphorylated tau according to the current 2021 National Institute on Neurological Disorders and Stroke/National Institute of Biomedical Imaging and Bioengineering consensus criteria for chronic traumatic encephalopathy. Five cases (0.79%) showed pathological evidence of chronic traumatic encephalopathy and three of these had a history of traumatic brain injury. Three cases had coexisting Alzheimer's and/or Lewy body disease pathology meeting criteria for neurodegenerative disease. Another eight cases almost met criteria for chronic traumatic encephalopathy neuropathological change except for an absence of neuronal tau or a strict perivascular arrangement. Ageing-related tau astrogliopathy was found in all eight cases as a coexisting neuropathology. Traumatic brain injury was associated with increased odds ratio [1.79, confidence interval 1.18-2.72] of having a higher neurofibrillary tangle stage and phosphorylated TAR DNA binding protein 43 (OR 2.48, confidence interval 1.35-4.54). Our study shows a very low rate of chronic traumatic encephalopathy neuropathological change in brains with or without neurodegenerative disease from the Sydney Brain Bank. Our evidence suggests that isolated traumatic brain injury in the general population is unlikely to cause chronic traumatic encephalopathy neuropathologic change but may be associated with increased brain ageing.

Systematic Review of Pre-injury Migraines as a Vulnerability Factor for Worse Outcome Following Sport-Related Concussion.

Background: Individuals with migraine disorders may be affected differently by concussions compared to individuals without migraine disorders. Prior studies on this topic have had mixed results. The purpose of this study was to systematically examine clinical outcomes following a sport-related concussion in athletes who have a pre-injury history of migraines. Methods: All studies published prior to 15 May 2021 that examined pre-injury migraines as a possible predictor of clinical recovery from concussion were included. The search included (i) sport/athlete-related terms, (ii) concussion-related terms, and (iii) diverse predictor/modifier terms. After removing duplicates, 5,118 abstracts were screened, 538 full-text articles were reviewed, and 27 articles were included for narrative synthesis without meta-analysis (n = 25 with unique samples). Risk of bias was assessed using the domain-based Quality In Prognosis Studies (QUIPS) tool. Results: Most studies did not find pre-injury migraines to be associated with concussion outcome, but several of these studies had small or very small sample sizes, as well as other methodological weaknesses. Risk of bias varied greatly across studies. Some of the larger, better-designed studies suggested pre-injury migraines may be a risk factor for worse concussion outcome. Most articles examined pre-injury migraines as an exploratory/secondary predictor of concussion outcome; very few were designed to examine migraine as the primary focus of the study. Migraine history was predominantly based on self-report and studies included minimal information about migraine (e.g., age of onset, frequency/severity, past treatment). Effect sizes were usually not reported or able to be calculated from reported study data. Conclusion: There is some evidence to suggest that pre-injury migraines may be a vulnerability factor for a worse outcome following concussion, with studies having the lowest risk of bias reporting a positive association. Future studies should focus on improving methodological quality when assessing the relationship between pre-injury migraines and concussion outcome and better characterizing pre-injury migraine status. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019128292, identifier: PROSPERO 2019 CRD42019128292.

Examining for Cavum Septum Pellucidum and Ventricular Enlargement in Retired Elite-Level Rugby League Players.

Objective: A cavum septum pellucidum (CSP) has been reported as a visible brain anomaly in normal individuals as well in some former combat and collision sport athletes. The appearance of CSP with fenestrations and ventricular enlargement are considered associated features of the neuropathological diagnosis of chronic traumatic encephalopathy. The current study examined CSP anatomic features and lateral ventricle size in retired elite rugby league players and controls. Methods: Forty-one retired rugby league players and 41 healthy community controls, similar in age and education, underwent structural MRI scans. CSP grade, CSP length, corpus callosum septal length, and Evans' ratio (for lateral ventricle size) were rated by two of the current study authors. All participants also self-reported concussion exposure histories, depressive symptoms, daytime sleepiness, and impulsivity. They completed a neuropsychological test battery assessing premorbid intellectual functioning, attention, processing speed, language, visuospatial skills, memory, and aspects of executive functioning. Results: The two raters had high agreement for CSP grade (Cohen's κ = 0.80), CSP length [intraclass correlation (ICC) = 0.99], corpus callosum septal length (ICC = 0.73), the CSP/septal ratio (ICC = 0.99), and the Evans' ratio (ICC = 0.75). Twenty-five retired players (61.0%) had an abnormal CSP compared to 17 controls [41.5%; χ ( 1 ,   82 ) 2 = 3.12, p = 0.08, odds ratio = 2.21]. The CSP/septal ratio was larger for retired players than for the controls. The Evans' ratio did not differ between the two groups. In the retired rugby league players (n = 41), those with normal (n = 16) and abnormal (n = 25) CSP grades did not differ across age, age of first exposure to collision sport, years of sport exposure, concussion history, or 23 clinical and cognitive variables. Conclusion: This study revealed a difference in the size of the CSP between retired professional rugby league players and controls. There was no significant difference in the size of the ventricles between the two groups. There were no significant differences between those with vs. without an abnormal CSP on age of first exposure to rugby league, years of exposure to repetitive neurotrauma, number of lifetime concussions, depression, impulsivity, perceived cognitive decline, or on any neuropsychological test.

Tacklers' Head Inertial Accelerations Can Be Decreased by Altering the Way They Engage in Contact with Ball Carriers' Torsos.

PURPOSE: This study aimed to investigate how four types of successfully executed, legal front-on, one-on-one torso tackles influence the tacklers' and ball carriers' inertial head kinematics. METHODS: A total of 455 successful front-on, one-on-one torso tackle trials completed by 15 rugby code players using three-dimensional motion capture were recorded. Tackles differed with respects to the height of the contact point on the ball carrier's torso. A series of mixed general linear models were conducted. RESULTS: The tackler sustained the highest peak resultant linear ( P < 0.001) and angular ( P < 0.01) head accelerations when contacting the lower torso to execute a "dominant" tackle compared with mid or upper torso, although these latter tackle types had the lowest ball carrier inertial head kinematics. When executing a "smother" tackle technique, a significant decrease in peak resultant linear head acceleration was observed with a vertical "pop" then lock action used, compared with the traditional upper torso tackling technique ( P < 0.001). CONCLUSIONS: Modifying the tackler's engagement with a ball carrier's torso, with respect to height and technical execution, alters the inertial head kinematics of the tackler and the ball carrier. The traditional thinking about optimal tackle technique, as instructed, may need to be reevaluated, with the midtorso being a potential alternative target contact height, whereas changes in tackle execution may be relatively protective for tacklers when executing either a dominant or smother tackle. This study provides critical scientific evidence to underpin revised coaching tackling technique interventions that might enhance player safety. Tackles in which the tackler contacts the ball carrier around the midtorso region, rather than lower torso, produce the lowest acceleration and thus may contribute to reducing head injury risk for the tackler.

Incidence of Concussion and Time to Return-to-Play in the National Rugby League.

OBJECTIVES: To examine the rates of concussion and recovery time over the course of 2 seasons of the National Rugby League (NRL). DESIGN: Descriptive cohort study. SETTING: The NRL match play concussion injury surveillance system. PARTICIPANTS: All NRL players who participated in the 2017 and 2018 season. MAIN OUTCOME MEASURES: The (1) frequency of sideline injury surveillance identified head impact events in real-time during the games, (2) frequency of head injury assessments conducted by the medical staff, (3) frequency of medically diagnosed concussions, (4) number of days to medical clearance to return-to-play, and (5) number of games missed after concussion. MAIN RESULTS: There were 472 head injury assessments conducted during the games and 149 medically diagnosed concussions over the course of 2 NRL seasons (1 concussion every 2.70 games). The median number of days until medical clearance was 6 (M = 6.85, SD = 8.03, interquartile range = 4-7; range = 0-79 days). There was a statistically significant difference in the number of days to be medically cleared to return to full contact or match play between seasons (U = 3517.00, P = 0.001), and the percentage of players medically cleared to return-to-play at 5 days after injury was 60.6% in 2017 and 27.6% in 2018. Most players (87.9%) did not miss a game after injury. CONCLUSIONS: There is approximately one concussion sustained for every 3 games in the NRL. Most players are medically cleared to return-to-play in 4 to 7 days.

Development of a Machine-Learning-Based Classifier for the Identification of Head and Body Impacts in Elite Level Australian Rules Football Players.

Background: Exposure to thousands of head and body impacts during a career in contact and collision sports may contribute to current or later life issues related to brain health. Wearable technology enables the measurement of impact exposure. The validation of impact detection is required for accurate exposure monitoring. In this study, we present a method of automatic identification (classification) of head and body impacts using an instrumented mouthguard, video-verified impacts, and machine-learning algorithms. Methods: Time series data were collected via the Nexus A9 mouthguard from 60 elite level men (mean age = 26.33; SD = 3.79) and four women (mean age = 25.50; SD = 5.91) from the Australian Rules Football players from eight clubs, participating in 119 games during the 2020 season. Ground truth data labeling on the captures used in this machine learning study was performed through the analysis of game footage by two expert video reviewers using SportCode and Catapult Vision. The visual labeling process occurred independently of the mouthguard time series data. True positive captures (captures where the reviewer directly observed contact between the mouthguard wearer and another player, the ball, or the ground) were defined as hits. Spectral and convolutional kernel based features were extracted from time series data. Performances of untuned classification algorithms from scikit-learn in addition to XGBoost were assessed to select the best performing baseline method for tuning. Results: Based on performance, XGBoost was selected as the classifier algorithm for tuning. A total of 13,712 video verified captures were collected and used to train and validate the classifier. True positive detection ranged from 94.67% in the Test set to 100% in the hold out set. True negatives ranged from 95.65 to 96.83% in the test and rest sets, respectively. Discussion and conclusion: This study suggests the potential for high performing impact classification models to be used for Australian Rules Football and highlights the importance of frequencies <150 Hz for the identification of these impacts.

A Case-Control Study of Tackle-Based Head Injury Assessment (HIA) Risk Factors in the National Rugby League.

BACKGROUND: The tackle is the in-game activity carrying the greatest risk for concussion in rugby. A recent evaluation of tackle characteristics in rugby union precipitated a rule modification to reduce head impact risk during tackles. This study aims to replicate the work conducted in rugby union by examining the association between tackle characteristics and head injury events in professional rugby league. METHODS: There were 446 tackles resulting in a head injury assessment (HIA) and 5,694 tackles that did not result in a head injury from two National Rugby League (NRL) seasons that were reviewed and coded. Tackle height, body position of players, and contact area on an opponent's body were evaluated, with the propensity of each situation to cause an HIA calculated as HIAs per 1000 events. RESULTS: The propensity for tacklers to sustain a head injury was 0.99 HIAs per 1000 tackles, 1.74-fold greater than for the ball carrier (0.57 HIAs per 1000 tackles). There was a 3.2-fold higher risk for an HIA when the tackler was upright compared to bent-at-the-waist. The greatest risk of a tackler HIA occurred when head contact was very low (knee, boot) or high (head and elbow). HIAs were most common following head-to-head impacts. The lowest propensity for tackler HIA was found when the tackler's head was in proximity with the ball carrier's torso. CONCLUSIONS: The result of this study replicated the findings in professional rugby union. This has implications for the injury prevention initiatives implemented to reduce HIA risk because the majority of injuries are sustained by the tackler.

Predictors and Correlates of Perceived Cognitive Decline in Retired Professional Rugby League Players.

Objective: Rugby league is an international full-contact sport, with frequent concussive injuries. Participation in other full-contact sports such as American football has been considered to be a risk factor for neuropsychiatric sequelae later-in-life, but little research has addressed the mental and cognitive health of retired professional rugby league players. We examined predictors and correlates of perceived (self-reported) cognitive decline in retired National Rugby League (NRL) players. Methods: Participants were 133 retired male elite level rugby league players in Australia. Participants completed clinical interviews, neuropsychological testing, and self-report measures. The Informant Questionnaire on Cognitive Decline in the Elderly, self-report (IQCODE-Self), measured perceived cognitive decline. Results: The median age of the sample was 55.0 (M = 53.1, SD = 13.9, range = 30-89) and the median years of education completed was 12.0 (M = 11.9, SD = 2.6, range = 7-18). The retired players reported a median of 15.0 total lifetime concussions (M = 28.0, SD = 36.6, range = 0-200). The mean IQCODE-Self score was 3.2 (SD = 0.5; Range = 1.3-5.0); 10/133 (7.5%) and 38/133 (28.6%) scored above conservative and liberal cutoffs for cognitive decline on the IQCODE-Self, respectively. Perceived cognitive decline was positively correlated with current depressive symptoms, negatively correlated with years of professional sport exposure and resilience, and unrelated to objective cognition and number of self-reported concussions. A multiple regression model with perceived cognitive decline regressed on age, concussion history, professional rugby league exposure, depression, resilience, objective cognitive functioning, daytime sleepiness, and pain severity showed depression as the only significant predictor. Conclusion: This is the first large study examining subjectively experienced cognitive decline in retired professional rugby league players. Similar to studies from the general population and specialty clinics, no relationship was found between objective cognitive test performance and perceived cognitive decline. Depressive symptoms emerged as the strongest predictor of perceived cognitive decline, suggesting that subjective reports of worsening cognition in retired elite rugby league players might reflect psychological distress rather than current cognitive impairment.

Video Analysis and Verification of Direct Head Impacts Recorded by Wearable Sensors in Junior Rugby League Players.

BACKGROUND: Rugby league is a high-intensity collision sport that carries a risk of concussion. Youth athletes are considered to be more vulnerable and take longer to recover from concussion than adult athletes. PURPOSE: To review head impact events in elite-level junior representative rugby league and to verify and describe characteristics of X-patchTM-recorded impacts via video analysis. STUDY DESIGN: Observational case series. METHODS: The X-patchTM was used on twenty-one adolescent players (thirteen forwards and eight backs) during a 2017 junior representative rugby league competition. Game-day footage, recorded by a trained videographer from a single camera, was synchronised with X-patchTM-recorded timestamped events. Impacts were double verified by video review. Impact rates, playing characteristics, and gameplay situations were described. RESULTS: The X-patchTM-recorded 624 impacts ≥ 20g between game start and finish, of which 564 (90.4%) were verified on video. Upon video review, 413 (73.2%) of all verified impacts ≥ 20g where determined to be direct head impacts. Direct head impacts ≥ 20g occurred at a rate of 5.2 impacts per game hour; 7.6 for forwards and 3.0 for backs (range = 0-18.2). A defender's arm directly impacting the head of the ball carrier was the most common event, accounting for 21.3% (n = 120) of all impacts, and 46.7% of all "hit-up" impacts. There were no medically diagnosed concussions during the competition. CONCLUSION: The majority (90.4%) of head impacts ≥ 20g recorded by the X-patchTM sensor were verified by video. Double verification of direct head impacts in addition to cross-verification of sensor-recorded impacts using a secondary source such as synchronised video review can be used to ensure accuracy and validation of data.