A systematic review of concussion in rugby league

The Impact of Drop Test Conditions on Brain Strain Location and Severity: A Novel Approach Using a Deep Learning Model

In contact sports such as rugby, players are at risk of sustaining traumatic brain injuries (TBI) due to high-intensity head impacts that generate high linear and rotational accelerations of the head. Previous studies have established a clear link between high-intensity head impacts and brain strains that result in concussions. This study presents a novel approach to investigating the effect of a range of laboratory controlled drop test parameters on regional peak and mean maximum principal strain (MPS) predictions within the brain using a trained convolutional neural network (CNN). The CNN is publicly available at https://github.com/Jilab-biomechanics/CNN-brain-strains . The results of this study corroborate previous findings that impacts to the side of the head result in significantly higher regional MPS than forehead impacts. Forehead impacts tend to result in the lowest region-averaged MPS values for impacts where the surface angle was at 0° and 45°, while side impacts tend to result in higher regional peak and mean MPS. The absence of a neck in drop tests resulted in lower regional peak and mean MPS values. The results indicated that the relationship between drop test parameters and resulting regional peak and mean MPS predictions is complex. The study's findings offer valuable insights into how deep learning models can be used to provide more detailed insights into how drop test conditions impact regional MPS. The novel approach used in this paper to predict brain strains can be applied in the development of better methods to reduce the brain strain resulting from head accelerations such as protective sports headgear.

I won't let you down; why 20% of Men's and Women's Super League players underreported suspected concussions

OBJECTIVES

Quantify and identify factors associated with concussion underreporting in Super League rugby league players.

DESIGN

Cross sectional survey.

METHODS

During the 2022 season preseason, 422 Men's and Women's Super League players completed an online survey quantifying player demographics, rugby playing history, concussion history, prevalence of, and reasons for underreporting concussion, concussion knowledge and long-term implications and perceptions of concussion.

RESULTS

Overall, 20% of respondents stated they did not report concussion-related symptoms to medical staff during the 2020 and 2021 seasons. The two most common reasons for underreporting concussion were 'didn't want to be ruled out of a match' (35%) and 'didn't want to let down team' (24%). 65% of players reported an appropriate level of knowledge about concussion and potential long-term implications at the start of their senior rugby career, versus 89% now. In relation to concussion knowledge, symptoms were correctly identified on 74% of occasions. 57% of players surveyed were concerned about the potential long-term implications from concussion, and 11% of players would encourage their/family members' children to not play rugby league.

CONCLUSIONS

The proportion of Super League players who did not report concussion symptoms was similar to rugby league players in Australia. The main reasons for not reporting concussion appeared to be due to perceptions of what is beneficial for the team, suggesting both performance and medical staff should collectively encourage players to report concussion. A player's attitude towards concussion is potentially an individual modifiable risk factor and should be considered within the concussion management of players.

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.

Concussion-Associated Gene Variant COMT rs4680 Is Associated With Elite Rugby Athlete Status

OBJECTIVE

Concussions are common match injuries in elite rugby, and reports exist of reduced cognitive function and long-term health consequences that can interrupt or end a playing career and produce continued ill health. The aim of this study was to investigate the association between elite rugby status and 8 concussion-associated risk polymorphisms. We hypothesized that concussion-associated risk genotypes and alleles would be underrepresented in elite rugby athletes compared with nonathletes.

DESIGN

A case-control genetic association study.

SETTING

Institutional (university).

PARTICIPANTS

Elite White male rugby athletes [n = 668, mean (SD) height 1.85 (0.07) m, mass 102 (12) kg, and age 29 (7) years] and 1015 nonathlete White men and women (48% men).

INTERVENTIONS

Genotype was the independent variable, obtained by PCR of genomic DNA using TaqMan probes.

MAIN OUTCOME MEASURE

Elite athlete status with groups compared using χ 2 and odds ratio (OR).

RESULTS

The COMT rs4680 Met/Met (AA) genotype, Met allele possession, and Met allele frequency were lower in rugby athletes (24.8%, 74.6%, and 49.7%, respectively) than nonathletes (30.2%, 77.6%, and 54.0%; P < 0.05). The Val/Val (GG) genotype was more common in elite rugby athletes than nonathletes (OR 1.39, 95% confidence interval 1.04-1.86). No other polymorphism was associated with elite athlete status.

CONCLUSIONS

Elite rugby athlete status is associated with COMT rs4680 genotype that, acting pleiotropically, could affect stress resilience and behavioral traits during competition, concussion risk, and/or recovery from concussion. Consequently, assessing COMT rs4680 genotype might aid future individualized management of concussion risk among athletes.

Sport level and sex differences in sport-related concussion among Japanese collegiate athletes: Epidemiology, knowledge, reporting behaviors, and reported symptoms

This study investigated the incidence of sport-related concussion (SRC) in sports, effect of athlete knowledge on reporting behavior differences between collegiate and non-collegiate athletes, and differences in SRC symptoms between sexes and level of participation. In this cross-sectional survey, 1 344 Japanese collegiate and non-collegiate athletes from a single institute were analyzed. Using a web-based survey, demographics, general SRC, knowledge of SRC, the most recent SRC reporting behaviors, and symptom presentation were examined. The prevalence of SRC during the academic year 2016-2017 was 2.68 (95% confidence interval [CI]: 1.88-3.69) across all sports. The prevalence of SRC was 33.3 (95% CI: 17.96-51.83) in rugby union and 8.33 (95% CI: 1.03-27.00) in women's soccer. The prevalence of SRC in males (3.47 [95% CI: 2.38-4.86] was 3.65 times higher than that in females (0.95 [95% CI: 0.26-2.41]). In total, the mean total score of knowledge was 5.30 (4.2) across 25 questions; dizziness was the most well-known symptom (867/1 344, 64.5%), followed by headache (59.3%). Being more emotional (44/1 345, 3.3%) was the least frequently known symptom. Level of participation did not affect scores (5.16 [3.96] vs. 5.52 [4.54]; p ​= ​0.131). All 87 disclosing participants experienced drowsiness and irritability and felt more emotional. In terms of sex and participant level, no significant differences were found in any symptoms. This study found very low rates of concussion education in Japan. Dissemination of concussion education is essential in the future to recognize concussion earlier and prevent severe concussive injury.

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.

Salivary microRNA as a prospective tool for concussion diagnosis and management: A scoping review

BACKGROUND

Despite increased efforts directed toward research, concussions are a growing concern and can be a complex injury for healthcare professionals to manage. Current practices are largely dependent on patients self-reporting symptoms and a clinical assessment, which uses objective tools that lack effectiveness. With the demonstrated effects of concussions, it is imperative that a more valid or reliable objective tool, like a clinical biomarker, be identified to improve outcomes. One potential biomarker that has shown promise is salivary microRNA. However, there is no objective consensus as to which microRNA offers the most clinical value regarding concussions, hence this review. Therefore, the purpose of this scoping review was to identify salivary miRNAs associated with concussions.

METHODS

Two independent reviewers performed a literature search to identify research articles. Studies using human subjects, collected salivary miRNA, and were published in English were included. Data of interest were salivary miRNA, collection timing, and relation to concussion diagnosis or management.

RESULTS

This paper reviews nine studies that analyzed salivary miRNA for concussion diagnosis and management.

CONCLUSIONS

In total, the studies have identified 49 salivary miRNA that show promise in assisting with concussion practices. With continued research, the use of salivary miRNA may enhance clinicians' abilities to diagnose and manage concussions.

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 ± 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.

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.

Drop Test Kinematics Using Varied Impact Surfaces and Head/Neck Configurations for Rugby Headgear Testing

World Rugby employs a specific drop test method to evaluate headgear performance, but almost all researchers use a different variation of this method. The aim of this study was, therefore, to quantify the differences between variations of the drop testing method using a Hybrid III headform and neck in the following impact setups: (1) headform only, with a flat steel impact surface, approximating the World Rugby method, (2 and 3) headform with and without a neck, respectively, onto a flat MEP pad impact surface, and (4) headform and neck, dropped onto an angled MEP pad impact surface. Each variation was subject to drop heights of 75-600 mm across three orientations (forehead, side, and rear boss). Comparisons were limited to the linear and rotational acceleration and rotational velocity for simplicity. Substantial differences in kinematic profile shape manifested between all drop test variations. Peak accelerations varied highly between variations, but the peak rotational velocities did not. Drop test variation also significantly changed the ratios of the peak kinematics to each other. This information can be compared to kinematic data from field head impacts and could inform more realistic impact testing methods for assessing headgear.

The Incidence, Cost, and Burden of Concussion in Women's Rugby League and Rugby Union: A Systematic Review and Pooled Analysis

BACKGROUND

The extent of concussion injury in the rugby codes for women is unclear.

OBJECTIVE

Our aim was to review all published studies reporting concussion injuries from match and training participation in rugby codes and report the pooled data estimates for rugby league and union concussion injury epidemiology.

METHODS

We conducted a systematic literature analysis of concussion in rugby league and rugby union for published studies from January 1990 to July 2021. Data from 16 studies meeting the inclusion criteria were extracted for women's concussion injuries and were subsequently pooled. Costs from Accident Compensation Corporation (ACC) data were attributed to the results to provide cost estimates.

RESULTS

The pooled analysis match injury incidence of women's concussion was higher for rugby league (10.3 per 1000 match hours) than rugby 15 s (2.8 per 1000 match hours) or rugby 7 s (8.9 per 1000 match hours). There was a fourfold difference in the pooled incidence of concussion in women's rugby league (risk ratio [RR] 4.53, 95% confidence interval [CI] 1.8-11.3]; p = 0.0001) when compared with rugby 15 s. There was also a ninefold higher risk of a concussion during match participation compared with training participation for women's rugby 15 s (RR 9.3, 95% CI 1.29-66.78; p = 0.0070). The total estimated costs for the concussions reported were NZ$1,235,101. For rugby 7 s, the pooled concussive injury burden was 33.2 days.

CONCLUSIONS

Our pooled analysis clarified the extent of concussion injury and the possible associated costs at several levels of the game for women's rugby codes. The pooled mean days lost because of concussions was 33 days. As this was considerably longer than the 7- to 10-day expected timeframe outlined in the Concussion in Sport Consensus statement, these guidelines need to be updated to include sex-specific differences.

Blink duration is increased in concussed youth athletes: a validity study using eye tracking in male youth and adult athletes of selected contact sports

OBJECTIVE

Diagnosing a sports-related concussion (SRC) remains challenging, and research into diagnostic tools is limited. This study investigated whether selected eye tracking variables would be a valid tool to diagnose and monitor SRC in adult and youth participants in selected contact sports, such as Rugby Union (rugby) and football (soccer).

METHODS

This prospective cohort study, with 70 concussed and 92 non-concussed adult and youth athletes, assessed the validity of five previously selected eye tracking variables for SRC diagnostics and management. The performance between concussed and age-matched control (non-concussed) athletes, as well as between three successive testing sessions in the concussed athletes were compared. Self-paced saccade count in adult group; blink duration in the memory-guided saccade and sinusoidal smooth pursuit tasks, proportion of antisaccade errors, and gain of diagonal smooth pursuit in the youth group were assessed.

RESULTS

The youth concussed group had higher blink duration in the fast memory-guided saccades task (p = 0.001, η2 = 0.17) and a tendency for higher blink duration in the sinusoidal smooth pursuit task (p = 0.016, η2 = 0.06) compared to the youth control group. In both tasks the blink duration in the concussed youth group decreased from session 1 to session 2 by 24% and 18%, accordingly, although statistical significance was not reached. The concussed adult group demonstrated a lower number of self-paced saccades compared to controls (p = 0.05, η2 = 0.09), which gradually increased, with the largest difference between session 1 and session 3 (p = 0.02).

CONCLUSIONS

Blink duration in youth athletes holds promise as a valid metric for concussion diagnostics and monitoring. It is recommended to focus future studies on comparing eye tracking performance within the same concussed athletes over time rather than comparing them to healthy controls.

Concussion-Associated Polygenic Profiles of Elite Male Rugby Athletes

Due to the high-velocity collision-based nature of elite rugby league and union, the risk of sustaining a concussion is high. Occurrence of and outcomes following a concussion are probably affected by the interaction of multiple genes in a polygenic manner. This study investigated whether suspected concussion-associated polygenic profiles of elite rugby athletes differed from non-athletes and between rugby union forwards and backs. We hypothesised that a total genotype score (TGS) using eight concussion-associated polymorphisms would be higher in elite rugby athletes than non-athletes, indicating selection for protection against incurring or suffering prolonged effects of, concussion in the relatively high-risk environment of competitive rugby. In addition, multifactor dimensionality reduction was used to identify genetic interactions. Contrary to our hypothesis, TGS did not differ between elite rugby athletes and non-athletes (p ≥ 0.065), nor between rugby union forwards and backs (p = 0.668). Accordingly, the TGS could not discriminate between elite rugby athletes and non-athletes (AUC ~0.5), suggesting that, for the eight polymorphisms investigated, elite rugby athletes do not have a more ‘preferable’ concussion-associated polygenic profile than non-athletes. However, the COMT (rs4680) and MAPT (rs10445337) GC allele combination was more common in rugby athletes (31.7%; p < 0.001) and rugby union athletes (31.8%; p < 0.001) than non-athletes (24.5%). Our results thus suggest a genetic interaction between COMT (rs4680) and MAPT (rs10445337) assists rugby athletes in achieving elite status. These findings need exploration vis-à-vis sport-related concussion injury data and could have implications for the management of inter-individual differences in concussion risk.

How is Video Efficient to Diagnose Sport-Related Concussion? A Cross-Sectional Study in the French TOP14 Rugby Championship

OBJECTIVE

To describe the frequency of clinical signs and the accuracy of video diagnosis of sport-related concussion.

DESIGN

An observational cross-sectional study.

SETTING AND PARTICIPANTS

Videos from a database of all suspected sport-related concussion in TOP14 matches (French professional male rugby Championship) were used, from 2012 to 2015 seasons. The videos were analyzed by 4 observers, blinded to the concussion diagnosis, after a training phase, and an inter-rater reliability analysis.

INTERVENTIONS

N/A.

MAIN OUTCOME MEASURES

Video analysis for clinical signs and presumed diagnosis of sport-related concussion. The observer's diagnosis was compared with the team physicians' diagnosis.

RESULTS

Four hundred seventeen videos were analyzed with 142 concussed players. Sport-related concussions happened mostly from an impact to the head (seen by the observers in 98.4%), against an opponent (73.2%), and during a tackle (74.6%). Video signs were observable in 98.6% for suspected loss of consciousness, tonic posturing (95%), ataxia (77.2%), dazed look (35.7%), abnormal behavior (18.2%), and seizures (96.2%). Ataxia was seen in 77.7% of concussed players, suspected loss of consciousness in 61.4%, dazed look in 63.2%, abnormal behavior in 55%, and tonic posturing in 7.1%. The observers diagnosed 79.8% of concussions.

CONCLUSIONS

We described the frequency of video clinical signs of sport-related concussion, with a good accuracy of the blinded observers for the diagnosis. This emphasizes the importance of pitch-side video analysis as an extra tool for sport-related concussion diagnosis.

Safeguarding Athletes Against Head Injuries Through Advances in Technology: A Scoping Review of the Uses of Machine Learning in the Management of Sports-Related Concussion

Sports injury prevention is an important part of the athlete welfare and safeguarding research field. In sports injury prevention, sport-related concussion (SRC) has proved to be one of the most difficult and complex injuries to manage in terms of prevention, diagnosis, classification, treatment and rehabilitation. SRC can cause long-term health issues and is a commonly reported injury in both adult and youth athletes around the world. Despite increased knowledge of the prevalence of SRC, very few tools are available for diagnosing SRC in athletic settings. Recent technological innovations have resulted in different machine learning and deep learning methodologies being tested to improve the management of this complex sports injury. The purpose of this article is to summarize and map the existing research literature on the use of machine learning in the management of SRC, ascertain where there are gaps in the existing research and identify recommendations for future research. This is explored through a scoping review. A systematic search in the three electronic databases SPORTDiscus, PubMed and Scopus identified an initial 522 studies, of which 24 were included in the final review, the majority of which focused on machine learning for the prediction and prevention of SRC (N = 10), or machine learning for the diagnosis and classification of SRC (N = 11). Only 3 studies explored machine learning approaches for the treatment and rehabilitation of SRC. A main finding is that current research highlights promising practical uses (e.g., more accurate and rapid injury assessment or return-to-sport participation criteria) of machine learning in the management of SRC. The review also revealed a narrow research focus in the existing literature. As current research is primarily conducted on male adolescents or adults from team sports in North America there is an urgent need to include wider demographics in more diverse samples and sports contexts in the machine learning algorithms. If research datasets continue to be based on narrow samples of athletes, the development of any new diagnostic and predictive tools for SRC emerging from this research will be at risk. Today, these risks appear to mainly affect the health and safety of female athletes.

An update on pathophysiology and treatment of sports-mediated brain injury

Traumatic brain injury (TBI) is a neurological disorder which represents a major health issue worldwide. It causes mortality and disability among all group ages, caused by external force, sports-related events or violence and road traffic accidents. In the USA, approximately one-third people die annually due to injury and 1.7 million people suffer from traumatic brain injury. Every year in India around 1.6 million individuals suffer from sustain brain injury with 200,000 deaths and approximately one million person needed recovery treatment at any stage of time. Sports-related head impact and trauma has become an extremely controversial public health and medico-legal problem that accounts for 20% of all brain injury (including concussion). It is difficult to reverse the primary injury but the secondary injury can be minimized by using proper pharmacological intervention during the initial hours of injury. This article highlights the pathophysiology and types of TBI along with treatment therapies. Till date, there is no single medication that can decrease the progression of the disease so that symptomatic treatment is given to the patient by determining proper pathology. Recently various herbal medicine therapies and traditional supplements have been developed for TBI. Nutritional supplementation and nutraceuticals have exposed potential in the treatment of TBI when used before and after TBI. The compiled data will enable the readers to know the pathophysiology as well as the allopathic and natural remedies to treat the TBI.

Quantification of Head Acceleration Events in Rugby League: An Instrumented Mouthguard and Video Analysis Pilot Study

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.

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.

Conceptualising Rugby League Performance Within an Ecological Dynamics Framework: Providing Direction for Player Preparation and Development

Across team sports, it is critically important to appropriately define, evaluate and then aptly describe individual and team performance. This is of particular significance when we consider that performance models govern the direction of player preparation (short term) and development (long term) frameworks. Within the context of rugby league, this has traditionally been undertaken through hierarchical and linear processes. Such approaches have resulted in research and performance analysis techniques which aim to support these operational outcomes. Yet, these methods may deliver limited application on how or why match-play unfolds and therefore might be sub-optimal in providing insights to truly support coaches. In this paper, we propose the conceptualisation of rugby league performance through the lens of ecological dynamics, which may offer a different view to this traditional approach. We propose that this approach eliminates the silos of disciplinary information (e.g. technical, physical and medical) that may currently exist, allowing for a holistic approach to performance, preparation and development. Specifically, we consider that through the implementation of this ecological approach, all performance coaches (technical, physical and medical) may (co-)design learning environments that more collaboratively develop players for rugby league match-play. As a result, we put forward a new rugby league performance model from which preparation and development programs can be anchored toward. We conclude the paper by offering practical examples where these concepts are contextualised within the landscape familiar to practitioners working within rugby league.

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00377-9.

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.

Laboratory Validation of Instrumented Mouthguard for Use in Sport

Concussion is an inherent risk of participating in contact, combat, or collision sports, within which head impacts are numerous. Kinematic parameters such as peak linear and rotational acceleration represent primary measures of concussive head impacts. The ability to accurately measure and categorise such impact parameters in real time is important in health and sports performance contexts. The purpose of this study was to assess the accuracy of the latest HitIQ Nexus A9 instrumented mouthguard (HitIQ Pty. Ltd. Melbourne Australia) against reference sensors in an aluminium headform. The headform underwent drop testing at various impact intensities across the NOCSAE-defined impact locations, comparing the peak linear and rotational acceleration (PLA and PRA) as well as the shapes of the acceleration time-series traces for each impact. Mouthguard PLA and PRA measurements strongly correlated with (R² = 0.996 and 0.994 respectively), and strongly agreed with (LCCC = 0.997) the reference sensors. The root mean square error between the measurement devices was 1 ± 0.6g for linear acceleration and 47.4 ± 35 rad/s² for rotational acceleration. A Bland-Altman analysis found a systematic bias of 1% for PRA, with no significant bias for PLA. The instrumented mouthguard displayed high accuracy when measuring head impact kinematics in a laboratory setting.

An International Exploration of the Effect of Media Portrayals of Postconcussion Management on Concussion Identification in the General Public

BACKGROUND

Concussion portrayal in media broadcasts of sporting events may contribute to lack of public understanding regarding concussion.

METHODS

In total, 828 participants from Australia, New Zealand, and the United Kingdom completed a questionnaire assessing concussion knowledge. Participants were randomly assigned to either receive sports return-to-play (RTP) guideline information (RTP group) or not (no-RTP group). Participants viewed 12 short clips from televised rugby games and indicated whether they believed the player in each clip had sustained a concussion. Participants were then informed whether the player was removed, returned, or stayed in the game and again asked whether they thought a concussion had occurred.

RESULTS

Probability of reporting a likely concussion over all videos was 65.6%. When told a player's possible concussion was managed by removal from the game, participants were more likely to change their response from "no" (no concussion) to "yes" (concussion) than from "yes" to "no." When told the player stayed or returned to the game, participants were more likely to change their response from "yes" (concussion) to "no" (no concussion) than from "no" to "yes." There was no significant main effect for RTP guideline manipulation or interaction effect with RTP information.

CONCLUSION

Additional player's injury management information influenced participants' judgments of concussion occurrence. Results show that information provided via sports media broadcasts influenced viewers' perceptions of concussion and appropriate concussion management.

Cannabis and Athletic Performance

Cannabis is widely used for both recreational and medicinal purposes on a global scale. There is accumulating interest in the use of cannabis and its constituents for athletic recovery, and in some instances, performance. Amidst speculation of potential beneficial applications, the effects of cannabis and its two most abundant constituents, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), remain largely un-investigated. The purpose of this review is to critically evaluate the literature describing the effects of whole cannabis, THC, and CBD, on athletic performance and recovery. While investigations of whole cannabis and THC have generally shown either null or detrimental effects on exercise performance in strength and aerobic-type activities, studies of sufficient rigor and validity to conclusively declare ergogenic or ergolytic potential in athletes are lacking. The ability of cannabis and THC to perturb cardiovascular homeostasis warrants further investigation regarding mechanisms by which performance may be affected across different exercise modalities and energetic demands. In contrast to cannabis and THC, CBD has largely been scrutinized for its potential to aid in recovery. The beneficial effects of CBD on sleep quality, pain, and mild traumatic brain injury may be of particular interest to certain athletes. However, research in each of these respective areas has yet to be thoroughly investigated in athletic populations. Elucidating the effects of whole cannabis, THC, and CBD is pertinent for both researchers and practitioners given the widespread use of these products, and their potential to interact with athletes' performance and recovery.

The Neurological Consequences of Engaging in Australian Collision Sports

Collision sports are an integral part of Australian culture. The most common collision sports in Australia are Australian rules football, rugby union, and rugby league. Each of these sports often results in participants sustaining mild brain traumas, such as concussive and subconcussive injuries. However, the majority of previous studies and reviews pertaining to the neurological implications of sustaining mild brain traumas, while engaging in collision sports, have focused on those popular in North America and Europe. As part of this 2020 International Neurotrauma Symposium special issue, which highlights Australian neurotrauma research, this article will therefore review the burden of mild brain traumas in Australian collision sports athletes. Specifically, this review will first provide an overview of the consequences of mild brain trauma in Australian collision sports, followed by a summary of the previous studies that have investigated neurocognition, ocular motor function, neuroimaging, and fluid biomarkers, as well as neuropathological outcomes in Australian collision sports athletes. A review of the literature indicates that although Australians have contributed to the field, several knowledge gaps and limitations currently exist. These include important questions related to sex differences, the identification and implementation of blood and imaging biomarkers, the need for consistent study designs and common data elements, as well as more multi-modal studies. We conclude that although Australia has had an active history of investigating the neurological impact of collision sports participation, further research is clearly needed to better understand these consequences in Australian athletes and how they can be mitigated.

The Applied Sports Science and Medicine of Netball: A Systematic Scoping Review

BACKGROUND

Netball is the one of the most popular women's sports in the world. Since gaining professional status in 2008 there has been a rapid growth in research in the applied sports science and medicine of the sport. A scoping review of the area would provide practitioners and researchers with an overview of the current scientific literature to support on-court performance, player welfare and reduce injury.

OBJECTIVE

The primary objective was to identify the current research on the applied sports science and medicine of netball. Additionally, the article provides a brief summary of the research in each topic of sports science and medicine in netball and identifies gaps in the current research.

METHODS

Systematic searches of PubMed, SPORTDiscus, MEDLINE and CINAHL were undertaken from earliest record to Dec 2020 and reference lists were manually searched. The PRISMA-ScR protocol was followed. Studies were eligible for inclusion if they investigated netball as a sport or the applied sport science and medicine of netball athletes.

RESULTS

962 studies were identified in the initial search, 150 of which met the inclusion criteria. Injury was the most highly investigated sport science and medicine topic (n = 45), followed by physical qualities (n = 37), match characteristics (n = 24), biomechanics (n = 15), psychology (n = 13), fatigue and recovery (n = 9), training load (n = 4) and nutrition (n = 3). A range of cohorts were used from school to elite and international standards. All cohorts were female netballers, except for one study. A rapid growth in studies over recent years was demonstrated with 65% of studies published in the last decade. There still remains gaps in the literature, with a low evidence base for nutrition, training load and fatigue and recovery.

CONCLUSION

This scoping review summarises the current evidence base and key findings that can be used in practice to enhance the applied sport science and medical support to netball athletes across a range of playing standards, and support the growth of the sport. It is evident that netball as a sport is still under-researched.

Athletes' and Coaches' Attitudes Toward Protective Headgear as Concussion and Head Injury Prevention: A Scoping Review

The purpose of this article is to map existing research literature on athletes and coaches' attitudes toward protective headgear in sport in relation to concussion and head injury prevention, and to identify and analyse knowledge gaps in the field. A scoping review was conducted in three databases; PubMed, Scopus, SportDiscus, and reference lists were searched to identify relevant grey literature. This process lead to an in-depth analysis of 18 peer-reviewed journal articles. Of the 18 studies identified, the majority focused on athletes (n = 14), only two studies focused on coaches, and two studies included a sample of both athletes and coaches. The findings in this scoping review suggests that there is a discrepancy between attitudes and beliefs about the protective effects of headgear, athletes' behaviour as far as wearing protective headgear, and coaches' behaviour in terms of recommending use of protective headgear to their athletes. The majority of athletes in most of the reviewed literature believed that headgear had protective effects against concussion and other head injuries, however relatively few athletes report wearing this protective headgear unless it was mandatory by competition rules.

Sport Concussion Assessment Tool-5th Edition (SCAT5): Normative Reference Values for the National Rugby League Women's Premiership

Objective: To establish normative reference values for the Sport Concussion Assessment Tool-5th Edition (SCAT5) for the new National Rugby League Women's Premiership. Methods: Preseason SCAT5 baseline testing was administered individually to all National Rugby League Women's Premiership players (N = 117). Testing was completed by the medical staff. Normative reference values were calculated for the components of the SCAT5, including the Standardized Assessment of Concussion, modified Balance Error Scoring System, and the Symptom Scale. A small case series of players who sustained concussions were included to illustrate the use of the new normative data. Results: The median Standardized Assessment of Concussion total score was 27.0 (M = 26.9, SD = 2.1). The median modified Balance Error Scoring System score was 2.0 (M = 2.4, SD = 2.2). The median number of symptoms score was 1.0 (M = 3.2, SD = 4.7) and the median symptom severity score was 2.0 (M = 5.4, SD = 8.2). The most common baseline symptom was fatigue or low energy (33%), followed by trouble sleeping (24%), headache (23%), neck pain (22%), and difficulty remembering (21%). In the total sample, 41% reported no symptoms. The clinical interpretation of these new normative data to a case series of women with concussions is provided. Conclusions: Normative reference values are provided for the SCAT5 for women who are professional rugby league players. Using these normative data will improve clinical interpretation of SCAT5 scores following a concussion.

Potential of Soft-Shelled Rugby Headgear to Reduce Linear Impact Accelerations

The purpose of this study was to examine the potential of soft-shelled rugby headgear to reduce linear impact accelerations. A hybrid III head form instrumented with a 3-axis accelerometer was used to assess headgear performance on a drop test rig. Six headgear units were examined in this study: Canterbury Clothing Company (CCC) Ventilator, Kukri, 2nd Skull, N-Pro, and two Gamebreaker headgear units of different sizes (headgears 1-6, respectively). Drop heights were 238, 300, 610, and 912 mm with 5 orientations at each height (forehead, front boss, rear, rear boss, and side). Impact severity was quantified using peak linear acceleration (PLA) and head injury criterion (HIC). All headgear was tested in comparison to a no headgear condition (for all heights). Compared to the no headgear condition, all headgear significantly reduced PLA and HIC at 238 mm (16.2-45.3% PLA and 29.2-62.7% HIC reduction; P < 0.0005, η p 2 = 0.987-0.991). Headgear impact attenuation lowered significantly as the drop height increased (32.4-5.6% PLA and 50.9-11.7% HIC reduction at 912 mm). There were no significant differences in PLA or HIC reduction between headgear units 1-3. Post hoc testing indicated that headgear units 4-6 significantly outperformed headgear units 1-3 and additionally headgear units 5 and 6 significantly outperformed headgear 4 (P < 0.05). The lowest reduction PLA and HIC was for impacts rear orientation for headgear units 1-4 (3.3 ± 3.6%-11 ± 5.8%). In contrast, headgear units 5 and 6 significantly outperformed all other headgear in this orientation (P < 0.0005, η p 2 = 0.982-0.990). Side impacts showed the greatest reduction in PLA and HIC for all headgear. All headgear units tested demonstrated some degree of reduction in PLA and HIC from a linear impact; however, units 4-6 performed significantly better than headgear units 1-3.

Predictors and Correlates of Depression in Retired Elite Level Rugby League Players

Background: There is considerable interest in determining whether later-in-life depression is associated with lifetime history of concussions or the duration of a career in professional contact and collision sports. Rugby league is a high-intensity collision sport involving a large number of tackles per game and a high rate of concussions. We examined predictors and correlates of depression in retired elite level rugby league players in Australia. Methods: Retired elite level rugby league players (N = 141, age: M = 52.6, SD = 13.8; Range = 30-89 years) completed the Depression, Anxiety, and Stress Scale (DASS), Brief Pain Inventory, Connor-Davidson Resilience Scale (CD-RISC), and Epworth Sleepiness Scale; they also reported on lifetime history of concussions. The DASS depression score was regressed on age, total number of self-reported concussions, years played professionally, CD-RISC score, BPI pain interference score, and ESS score. Results: The retired players reported a median of 15 total lifetime concussions [interquartile range (IQR) = 6-30], and a median of 8 years playing professional sports (IQR = 3.5-11). The proportion of the sample endorsing at least mild current depression was 29%. The DASS depression score was positively correlated with the DASS anxiety (r = 0.54) and DASS stress scores (r = 0.58). The CD-RISC score was negatively correlated with the depression score (r = -0.53). Depression scores were not significantly correlated with pain severity (r = 0.14), and were weakly correlated with life interference due to pain (r = 0.20) and years playing professional sports (r = -0.17). Depression scores were not significantly correlated with lifetime history of concussions (r = 0.14). A multiple regression model, with age, total number of self-reported concussions, years played professionally, the CD-RISC, Brief Pain Inventory-pain interference score, and Epworth Sleepiness Scale score as predictors was significant, with 35% of the variance in DASS depression accounted for. The two significant independent predictors of depression were lower resilience and greater life interference due to pain. Conclusions: This is the first large study of depression in retired rugby league players. Depression in these retired players was not meaningfully associated with lifetime history of concussions or number of years playing elite level collision sport. Depression was associated with current anxiety, stress, resilience, and life interference due to chronic pain.

Concussions, cuts and cracked bones: A systematic literature review on protective headgear and head injury prevention in Olympic boxing

In 2013, the International Boxing Association (AIBA) prohibited the use of headguards for elite male Olympic boxing competitions. Could the removal of the headguard from elite male boxing competitions potentially cause increased injury risk for boxers? The aim of the literature review is to analyse current knowledge about the use of protective headgear and injury prevention in boxing, in order to determine if there are increased injury risks associated with headguard use. Peer-reviewed studies (language: English, Norwegian, Swedish, Danish and Dutch) published from 1980 and onwards were considered. Five academic databases and grey literature sources were searched, and articles were assessed for methodological quality. Only studies that included boxers as the study population with headguards as a factor were considered. A total of 39 articles were included in the review. The analysis of the reviewed literature indicates that headguards protect well against lacerations and skull fractures, while less is known about the protective effects against concussion and other traumatic brain injuries. Most of the analysed studies however use indirect evidence, obtained through self-report or observational techniques with relatively small non-representative samples. There are almost no randomised control trials, longitudinal research designs or samples from recreational boxing. Therefore, AIBA's decision to remove the headguard has to be seen with caution and injury rates among (male) boxers should be continuously evaluated.

Head impact exposures in women's collegiate rugby

Objectives: To describe the incidence, magnitude, and distribution of head impacts and track concussions sustained in a collegiate level women's rugby season. Methods: Data on head impact incidence and magnitude were collected via Smart Impact Monitors (SIM) (Triax Technologies, Inc., Norwalk, CT) within fitted headbands during practices and games of one competitive season. Magnitude data included peak linear acceleration (PLA) and peak rotational velocity (PRV) measurements and were reported as median [IQR]. Results: Players sustained 120 head impacts ≥15 g (18.1 g - 78.9 g) with 1199 total athlete exposures. In eight games, 67 head impacts were recorded with a mean rate of 0.40 ± 0.22 hits per-player per-match, median PLA of 32.2 g, and PRV of 13.5 rad^.sec^-1. There were 53 head impacts in 47 practices with a mean rate of 0.05 ± 0.04 hits per-player per-practice, median PLA of 29.8 g and PRV of 15.7 rad^.sec^-1. Four concussions were reported and monitored. Conclusion: The incidence and magnitude of head impacts in collegiate level women's rugby over one season of practices and games were fewer than those reported in other comparable studies. These findings give insight into the impact burden that female collegiate rugby athletes withstand throughout a competitive season.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

White Matter Abnormalities in Retired Professional Rugby League Players with a History of Concussion

The topic of potential long-term neurological consequences from having multiple concussions during a career in collision sports is controversial. We sought to investigate white matter microstructure using diffusion tensor imaging (DTI) in retired professional Australian National Rugby League (NRL) players (n = 11) with a history of multiple self-reported concussions compared with age- and education-matched controls (n = 13) who have had no history of brain trauma. Diffusion-weighted images were acquired with a Siemens 3T scanner. All participants completed a clinical interview. There were no significant differences between groups on measures of depression, anxiety, stress, or post-concussion symptoms; however, NRL players scored significantly higher on the alcohol use disorder identification test (AUDIT). Voxelwise analyses of DTI measures were performed using tract-based spatial statistics (TBSS) with age and AUDIT scores included as covariates. TBSS revealed significantly reduced fractional anisotropy (FA), and increased radial diffusivity (RD), axial diffusivity (AD), and trace (TR) in white matter regions of recently retired NRL players compared with controls. FA was significantly reduced in the right superior longitudinal fasciculus and right corticospinal tract while TR, RD, and AD were increased in these regions, as well as the corpus callosum, forceps major, right uncinate fasciculus, and left corticospinal tract. In summary, DTI in a small cohort of recently retired professional NRL players with a history of multiple concussions showed differences in white matter microstructure compared with age- and education-matched controls with no history of brain trauma.

Functional Connectivity Changes in Retired Rugby League Players: A Data-Driven Functional Magnetic Resonance Imaging Study

There is considerable interest in the long-term brain health of retired contact and collision sport athletes; however, little is known about possible underlying changes in functional brain connectivity in this group. We evaluated whole-brain functional connectivity patterns using multi-voxel pattern analysis (MVPA) to determine whether alterations in functional connectivity distinguish retired professional athletes from a matched group of healthy community control subjects. Thirty-two retired athletes with a history of multiple self-reported sport-related concussions and 36 healthy community control subjects who were similar in age and education, completed functional magnetic resonance imaging. We identified brain regions with abnormal functional connectivity patterns using whole-brain MVPA as implemented in the Conn toolbox. First-level MVPA was performed using 64 principal component analysis (PCA) components. Second-level F test was performed using the first three MVPA components for retired athletes > controls group contrast. Post hoc seed-to-voxel analyses using the MVPA cluster results as seeds were performed to characterize functional connectivity abnormalities from brain regions identified by MVPA. MVPA revealed one cluster of abnormal functional connectivity located in cerebellar lobule V. This region of lobule V corresponded to the ventral attention network. Post hoc seed-to-voxel analysis using the cerebellar MVPA cluster as a seed revealed multiple areas of cerebral cortical hyper-connectivity and hypo-connectivity in retired athletes when compared with controls. This initial report suggests that cerebellar dysfunction might be present and clinically important in some retired athletes.

Retinal nerve fibre changes in sports-related repetitive traumatic brain injury

IMPORTANCE

There is limited literature on the use of optical coherence tomography in the assessment of retinal nerve fibre layer (RNFL) thickness in sports-related repetitive mild traumatic brain injury.

BACKGROUND

To evaluate RNFL thickness in professional rugby league players. RNFL thinning may serve as a proxy for wider white matter degeneration.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Thirteen retired Australian professional rugby league players were recruited.

METHODS

Participants underwent binocular optical coherence tomography to measure RNFL thickness. Each participant underwent a complete ophthalmic assessment to exclude concurrent disease.

MAIN OUTCOME MEASURES

RNFL thickness of each eye were compared with a normative database.

RESULTS

Participants had played professional Rugby League for 18 years on average and reported sustaining 15 sports-related concussions throughout their career. The RNFL in participants was four micrometres thinner than that of matched normative data. Cohort average RNFL thickness was reduced in 12 out of 14 optical coherence testing parameters. These findings were statistically significant in the left inferonasal [P = .013] and left nasal [P = .006] sectors. There was no statistically significant relationship between RNFL thickness and other visual measures.

CONCLUSIONS AND RELEVANCE

This study is the first to demonstrate RNFL thinning in a cohort of retired Australian professional Rugby League players. RNFL changes have been shown to correlate with cerebral white matter loss and neurodegeneration. Optical coherence tomography may serve as a safe and economical means of screening for repetitive traumatic brain injury related neurodegeneration in contact sport athletes.

High Concussion Rate in Student Community Rugby Union Players During the 2018 Season: Implications for Future Research Directions

Collision sports, such as Rugby Union (“Rugby”) have a particularly high risk of injury. Of all injuries common to collision sports, concussions have received the most attention due to the potentially negative cognitive effects in the short- and long-term. Despite non-professional Rugby players comprising the majority of the world’s playing population, there is relatively little research in this population. Stellenbosch Rugby Football Club (“Maties”), the official rugby club of Stellenbosch University, represents one of the world’s largest non-professional Rugby clubs, making this an ideal cohort for community-level injury surveillance. The aim of this study was to describe the incidence and events associated with concussion in this cohort. Baseline demographics were obtained on the 807 male student Rugby non-professional players who registered for the 10-week long 2018 season, which comprised 101 matches and 2,915 of exposure hours. All match-related injuries were captured by the medical staff of Stellenbosch Campus Health Service on an electronic form developed from the consensus statement for injury recording in Rugby. The mean age, height and weight of this cohort were 20 ± 2 years, 182 ± 7 cm and 88 ± 14 kg, respectively. Overall, there were 89 time-loss injuries, which equated to an injury rate of 30.6 per 1,000 match hours [95% confidence intervals (CIs): 24.2–36.9], or about one injury per match. The most common injury diagnosis was “concussion” (n = 27 out of 90 injuries, 30%), at a rate of 9.3 per 1,000 match hours (95% CIs: 5.8–12.8). The three most common mechanisms of concussion in the present study were performing a tackle (33%), accidental collision (30%) and being tackled (11%). Concussion was the most common injury in this population, at a rate that was six times higher than the most comparable study from the UK, which had far more exposure time over six seasons and wider range of player ability, from recreational to semi-professional. This might be explained by the training and vigilance of the club’s first aiders observing all matches for concussion. Future studies should try to explain this high rate and subsequently reduce these concussions. The addition of video surveillance data would assist in identifying the etiology of these concussions injuries in order to develop specific targeted interventions.

The Epidemiology of Sport-Related Concussion: What the Rehabilitation Clinician Needs to Know

Sport-related concussion is common in full-contact and collision sports. Epidemiology studies use different types of surveillance systems and concussion definitions. Concussion incidence rates vary across age, sex, sport, and level of competition. Incidence rates are increasing, likely due to higher rates of reporting following improved knowledge and increased regulations. In this review, we summarize 7 key concepts related to concussion epidemiology: concussion definition, changes in concussion knowledge, reliability and accuracy of injury surveillance systems, conservative management and return to play, reliability of self-report, incidence of concussion across levels of play, and understanding the behaviors of players, coaches, and medical personnel from a multidisciplinary management perspective. J Orthop Sports Phys Ther 2019;49(11):768-778. doi:10.2519/jospt.2019.9105.

The Demands of Professional Rugby League Match-Play: a Meta-analysis

Background

Rugby league is a collision sport, where players are expected to be physically competent in a range of areas, including aerobic fitness, strength, speed and power. Several studies have attempted to characterise the physical demands of rugby league match-play, but these studies often have relatively small sample sizes based on one or two clubs, which makes generalisation of the findings difficult. Therefore, the aim of this review was to synthesise studies that investigated the physical demands of professional rugby league match-play.

Methods

SPORTDiscus, CINAHL, MEDLINE (EBSCO) and Embase (EBSCO) databases were systematically searched from inception until October 2018. Articles were included if they (1) recruited professional rugby league athletes aged ≥ 18 years and (2) provided at least one match-play relevant variable (including playing time, total and relative distance, repeat high-intensity efforts (RHIE), efforts per RHIE, accelerations and decelerations, total and relative collisions). Meta-analyses were used to provide pooled estimates ± 95% confidence intervals.

Results

A total of 30 studies were included. Pooled estimates indicated that, compared to adjustables and backs, forwards have less playing time (− 17.2 ± 5.6 and − 25.6 ± 5.8 min, respectively), cover less ‘slow-speed’ (− 2230 ± 735 and − 1348 ± 655 m, respectively) and ‘high-speed’ distance (− 139 ± 108 and − 229 ± 101 m, respectively), but complete more relative RHIEs (+ 0.05 ± 0.05 and + 0.08 ± 0.04 per minute, respectively), and total (+ 12.0 ± 8.1 and + 12.8 ± 7.2 collisions, respectively) and relative collisions (+ 0.32 ± 0.22 and + 0.41 ± 0.22 collisions per minute, respectively). Notably, when the distance was expressed relative to playing time, forwards were not different from adjustables and backs in slow-speed (P ≥ 0.295) and high-speed (P ≥ 0.889) relative distance. The adjustables and backs subgroups were similar in most variables, except playing time (shorter for adjustables, − 8.5 ± 6.2 min), slow-speed distance (greater for adjustables, + 882 ± 763 m) and total relative distance (greater for adjustables, + 11.3 ± 5.2 m·min⁻¹). There were no significant differences between positional groups for efforts per RHIE, accelerations and decelerations (P ≥ 0.745).

Conclusions

These results indicate the unique physical demands of each playing position and should be considered by strength and conditioning and tactical coaches when planning for professional rugby league performance.

Protocol Registration

https://osf.io/83tq2/

Electronic supplementary material

The online version of this article (10.1186/s40798-019-0197-9) contains supplementary material, which is available to authorized users.

National Rugby League match scheduling and rate of concussion

OBJECTIVES

The aims of this study were to evaluate the relationship between pre-match rest days, match location, time of season, and match outcome with diagnosed concussion and use of the Concussion Interchange Rule (CIR) during the 2014 NRL season.

DESIGN

Descriptive observational study.

METHODS

This study reviewed all instances of diagnosed concussions, CIR activations, and match characteristics during the 2014 NRL season. Information pertaining to the use of the CIR was obtained from the league. Each club provided information of diagnosed concussion.

RESULTS

A total of 402 NRL games were analyzed, the concussion interchange rule was activated 167 times, and 60 concussions were diagnosed in 53 of the matches. A significantly greater proportion of concussions occurred during the first match of the season (38% vs. 15% of in-season matches; p=0.02). Days of rest, match location, season stage, and match outcome were not associated with a higher proportion of concussions. Furthermore, we did not detect a significant association between CIR activation and days of rest prior to the match, opponent rest prior to the match, match location, round of the season, or match outcome.

CONCLUSIONS

A significantly greater proportion of concussions were diagnosed during the first match of the season. Days between matches, opponent days of rest, match location, or other rounds (aside from round 1) of the season were not associated with CIR activation or diagnosed concussion. Varied game scheduling during the season does not appear to be associated with increased risk for concussion or use of the CIR in the NRL.

Verifying Head Impacts Recorded by a Wearable Sensor using Video Footage in Rugby League: a Preliminary Study

BACKGROUND

Rugby league is a full-contact collision sport with an inherent risk of concussion. Wearable instrumented technology was used to observe and characterize the level of exposure to head impacts during game play.

PURPOSE

To verify the impacts recorded by the x-patch™ with video analysis.

STUDY DESIGN

Observational case series.

METHODS

The x-patch™ was used on eight men's semi-professional rugby league players during the 2016 Newcastle Rugby League competition (five forwards and three backs). Game day footage was recorded by a trained videographer using a single camera located at the highest midfield location to verify the impact recorded by the x-patch™. Videographic and accelerometer data were time synchronized.

RESULTS

The x-patch™ sensors recorded a total of 779 impacts ≥ 20 g during the games, of which 732 (94.0%) were verified on video. In addition, 817 impacts were identified on video that did not record an impact on the sensors. The number of video-verified impacts ≥ 20 g, per playing hour, was 7.8 for forwards and 4.8 for backs (range = 3.9-19.0). Impacts resulting in a diagnosed concussion had much greater peak linear acceleration (M = 76.1 g, SD = 17.0) than impacts that did not result in a concussion (M = 34.2g, SD = 18.0; Cohen's d = 2.4).

CONCLUSIONS

The vast majority (94%) of impacts ≥ 20 g captured by the x-patch™ sensor were video verified in semi-professional rugby league games. The use of a secondary source of information to verify impact events recorded by wearable sensors is beneficial in clarifying game events and exposure levels.

Perceptual-cognitive three-dimensional multiple-object tracking task can help the monitoring of sport-related concussion

Objectives

While the rate of sport-related concussion is increasing, more effective tools are needed to help monitor the diagnosis and return to play of athletes. The three-dimensional multiple-object tracking (3D-MOT) exercise is a perceptual-cognitive task that has shown predictive power towards the dynamic requirements of real-world activities such as sport. This study introduced the use of the 3D-MOT task, along with the Standardized Assessment of Concussion (SAC) and Modified Balance Error Scoring System (M-BESS) tests, for diagnosis and return to play in professional sports.

Methods

Fifty-nine professional athletes were tested with the 3D-MOT, SAC and M-BESS tests at 48 hours following the injury. The same measures were employed to evaluate the return to play following the standard concussion management protocol. The SAC and M-BESS tests were also performed in pre-season (baseline) in 32 out of the 59 athletes.

Results

The injured athletes exhibited poor performance on 3D-MOT at 48 hours post injury compared with return to play (p<0.001) as well as compared with healthy professionals' performance scores (p<0.001). Importantly, learning rate, which participants are thought to have an expert advantage on this perceptual-cognitive task, was totally disrupted at 48 hours post injury compared with healthy professionals (p<0.001). The 3D-MOT performance was also correlated to the total number of symptoms (p=0.020), SAC (p=0.031) and M-BESS (p=0.004) scores at 48 hours. Not surprisingly, SAC and M-BESS tests' usefulness for monitoring concussion was found to be weak, particularly when test performance following the injury was compared to baseline (p=0.056 and 0.349 for SAC and M-BESS, respectively).

Conclusion

3D-MOT could help monitor sport-related concussion in professional athletes. The discussion also covers the critical importance of perceptual-cognitive assessment following concussion in the athletic population.

Concussion incidence in amateur Australian Rules Footballers

Australian Rules Football is a collision sport that is associated with increased sport-related concussion risk. Sport-related concussion is a common form of mild traumatic brain injury that is now recognised as a serious health issue. This study measured the concussion incidence rate for amateur Australian Rules players over 3 seasons (2015-2017) by athlete exposures-a metric used widely in the literature. This study also reported concussion incidence based on player match hours, a less common yet more accurate method of reporting concussion incidence which takes match duration into account. Accurate concussion incidence reporting in amateur Australian Rules Football quantifies the problem of concussion in this sport. This may be necessary to inform players of their concussion injury risk and to help guide rule changes to protect players from this injury.

Sport related concussion - Potential for biomarkers to improve acute management

Sport-related concussion is a common form of mild traumatic brain injury that is now recognised as a serious health issue. Growing evidence suggests concussion may result in long-term and severe neurological disabilities. Recent research into the diagnosis and management of concussion may provide new approaches to concussion management that limit the potential long-term adverse effects of concussion. This paper summarises the problem of sport-related concussion and reviews key factors (sex, age, genetics) that may modify concussion outcomes. Current sport-related concussion tools are described. Analysis of emerging methods of acute concussion diagnosis using objective fluid and neuroimaging biomarkers is provided. These new concussion biomarkers have the potential to change management of sport-related concussion.

Semi-Professional Rugby League Players have Higher Concussion Risk than Professional or Amateur Participants: A Pooled Analysis

A combined estimate of injuries within a specific sport through pooled analysis provides more precise evidence and meaningful information about the sport, whilst controlling for between-study variation due to individual sub-cohort characteristics. The objective of this analysis was to review all published rugby league studies reporting injuries from match and training participation and report the pooled data estimates for rugby league concussion injury epidemiology. A systematic literature analysis of concussion in rugby league was performed on published studies from January 1990 to October 2015. Data were extracted and pooled from 25 studies that reported the number and incidence of concussions in rugby league match and training activities. Amateur rugby league players had the highest incidence of concussive injuries in match activities (19.1 per 1000 match hours) while semi-professional players had the highest incidence of concussive injuries in training activities (3.1 per 1000 training hours). This pooled analysis showed that, during match participation activities, amateur rugby league participants had a higher reported concussion injury rate than professional and semi-professional participants. Semi-professional participants had nearly a threefold greater concussion injury risk than amateur rugby league participants during match participation. They also had nearly a 600-fold greater concussion injury risk than professional rugby league participants during training participation.

Neurophysiological and cognitive impairment following repeated sports concussion injuries in retired professional rugby league players

BACKGROUND

Concussion is regarded as a common injury in rugby league, however no studies have explored the long-term neurophysiological and cognitive effects of repeated concussion injuries in this sport.

METHODS

Former professional rugby athletes (n = 25) were compared to 25 age-matched participants with no history of a concussion. All participants completed standardised motor dexterity, reaction time, and cognitive tasks for working memory, associative learning and rule acquisition and reversal. Single-pulse transcranial magnetic stimulation (TMS) acquired motor evoked potentials and cortical silent period (cSP), as well as paired-pulse TMS for short latency intracortical inhibition and long intracortical inhibition (LICI).

RESULTS

Compared to controls, dexterity and visuomotor reaction time was slower in the rugby group compared to controls (p = 0.02, p < 0.01, respectively). The rugby group also demonstrated poorer cognitive performance than controls (p range 0.02 to < 0.01). TMS revealed significantly reduced cSP at suprathreshold stimulation intensities (p range 0.02 to <0.01), and increased LICI (p = 0.03) in the rugby group.

DISCUSSION

These findings of motor and cognitive changes, along with neurophysiological alterations, particularly with intracortical inhibition, nearly two decades post-concussion provides evidence for long-term sequelae for athletes with a history of repeated head trauma in contact sports.