Risk Factors for Concussion in Under 18, Under 22 and Professional Men's Rugby Union: A Video Analysis of 14,809 Tackles

OBJECTIVE

This study aimed to identify the risk factors for tackle-related concussion observed in matches involving under (U) 18, U 22 and professional men's Rugby Union players through video analysis.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Twenty Rugby Union matches each for high school (U18), university/college (U22) and professional (Elite) were randomly selected from 202 matches in the 2018/2019 season. Both one-on-one and tackles involving multiple tacklers were analyzed for the 60 matches. The 28 categorical and continuous variables (e.g., tackle characteristics and duration before the tackle) were applied as risk factors to a least absolute shrinkage and selection operator (Lasso) regression analysis. To identify high-risk situations, a simulation model with coefficients obtained from the Lasso regression was used. Statistical analysis was conducted according to tackle direction.

RESULTS

A total of 14,809 tackles and 41 concussions involving 1800 players were included in the analyses. The incidence rate of concussions (injuries/1000 tackles) was greater in Elite players (4.0) compared with U18 (1.9) and U22 (2.4) players. The factors most highly associated with concussions were head-in-front tackles (where the tackler's head is placed forward, impeding a ball carrier's forward movements, 11.26/1000 tackles), and were more often observed among U18 players. A simulation model predicted that the highest risk tackle situation in Elite players was a head-in-front, side-on tackle below the hip of the ball carrier (predicted incidence rate 18.07/1000 tackles).

CONCLUSION

The risk factors associated with concussion need to be assessed cautiously. Avoiding head-in-front, side-on tackles to the lower extremities of a ball carrier should be considered to reduce injury risks.

A comparison of activity demands between trial matches and in-season matches across multiple teams and seasons in semi-professional, male rugby league players

Trial matches are frequently used for team preparation in rugby league competitions, making it essential to understand the demands experienced to assess their specificity to actual competition. Consequently, this study aimed to compare the activity demands between pre-season trial matches and early in-season rugby league matches. Following a repeated-measures observational design, 39 semi-professional, male rugby league players from two clubs were monitored using microsensors during two trial matches and the first two in-season matches across two consecutive seasons. Total distance, average speed, peak speed, absolute and relative high-speed running (HSR; > 18 km · h-1) and low-speed running (LSR; < 18 km · h-1) distance, as well as absolute and relative impacts, accelerations (total and high-intensity > 3 m · s-2), and decelerations (total and high-intensity < -3 m · s-2) were measured. Linear mixed models and Cohen's d effect sizes were used to compare variables between match types. Playing duration was greater for in-season matches (p < 0.001, d = 0.64). Likewise, higher (p < 0.001, d = 0.45-0.70) activity volumes were evident during in-season matches indicated via total distance, HSR distance, LSR distance, total accelerations, high-intensity accelerations, total decelerations, and high-intensity decelerations. Regarding activity intensities, a higher average speed (p = 0.008, d = 0.31) and relative LSR distance (p = 0.005, d = 0.31) only were encountered during in-season matches. Despite players completing less volume, the average activity intensities and impact demands were mostly similar between trial and early in-season matches. These findings indicate trial matches might impose suitable activity stimuli to assist players in preparing for early in-season activity intensities.

A global perspective on collision and non-collision match characteristics in male rugby union: Comparisons by age and playing standard

This study quantified and compared the collision and non-collision match characteristics across age categories (i.e. U12, U14, U16, U18, Senior) for both amateur and elite playing standards from Tier 1 rugby union nations (i.e. England, South Africa, New Zealand). Two-hundred and one male matches (5911 min ball-in-play) were coded using computerised notational analysis, including 193,708 match characteristics (e.g. 83,688 collisions, 33,052 tackles, 13,299 rucks, 1006 mauls, 2681 scrums, 2923 lineouts, 44,879 passes, 5568 kicks). Generalised linear mixed models with post-hoc comparisons and cluster analysis compared the match characteristics by age category and playing standard. Overall significant differences (p < 0.001) between age category and playing standard were found for the frequency of match characteristics, and tackle and ruck activity. The frequency of characteristics increased with age category and playing standard except for scrums and tries that were the lowest at the senior level. For the tackle, the percentage of successful tackles, frequency of active shoulder, sequential and simultaneous tackles increased with age and playing standard. For ruck activity, the number of attackers and defenders were lower in U18 and senior than younger age categories. Cluster analysis demonstrated clear differences in all and collision match characteristics and activity by age category and playing standard. These findings provide the most comprehensive quantification and comparison of collision and non-collision activity in rugby union demonstrating increased frequency and type of collision activity with increasing age and playing standard. These findings have implications for policy to ensure the safe development of rugby union players throughout the world.

"It's always the bare minimum" - A qualitative study of players' experiences of tackle coaching in women's rugby union

OBJECTIVES

Tackle coaching forms a cornerstone of training in rugby and is designed to enhance performance and mitigate tackle injury. The athlete voice can help key stakeholders understand the psychosocial determinants that shape skill development in relation to tackle coaching. We aimed to capture player experiences of tackle coaching in women's rugby union.

DESIGN

Qualitative study using the grounded theory approach.

METHODS

Current women rugby union players, with at least 1-year senior level experience, were recruited from Europe, Africa and North America between December 2021 and March 2022 to participate in the study. Data were collected through semi-structured interviews and analysed in line with grounded theory coding procedures.

RESULTS

The 21 players were aged 20-48 years with a mean 10.6 years of rugby playing experience. Analysis revealed that the experiences of tackle coaching that shaped women's tackle skill development and sense of preparedness ranged from constraining to empowering, and gender was a pivotal influence in creating meaning. Participants expected and accepted the bare minimum in tackle coaching as the price that they had to pay for inclusion in rugby.

CONCLUSIONS

Participants' experiences of tackle coaching were entangled in inequitable club structures and cultures where men's rugby is the norm. Empowering tackle coaching in women's rugby union must be bespoke to the given context and the needs of women players. The recommendations offered in this paper encourage discussion as to how best to empower women's tackle development in rugby.

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.

Improper Fit in American Youth Football Helmets Across One Competitive Season

Improper helmet fit is related to sport-related concussion symptomology. The objective of this study was to determine the prevalence of improperly fit helmets in American youth tackle football players across one competitive season. Four recreation leagues including 147 players (45.2 ± 14.7 cm, 147.5 ± 9.0 kg), aged 7-12 years, participated in pre-season and post-season data collection timepoints. Participant and league demographics were collected at pre-season. Helmet fit was assessed at pre- and post-season using a 13-item checklist. A helmet was defined as improperly fit if failed to comply with or more of the checklist items. Most players (84%) rented helmets from the league. At preseason, 71.4% of helmets, and at post-season 79.6%, were improperly fit with no significant change over time (p = 0.14). Of the 105 improperly fit helmets at the start of the season, 61% were still considered improperly fit at post season. The 11-12 year old age group had significantly more improperly fit helmets than the 7-10 year old age group at post-season (p = 0.033), but not pre-season (p = 0.655). American youth football players depend on the league to fit their helmet. Most players did not meet at least one checklist criteria. Helmets improperly fit at preseason were still not fit at post.

Quantifying the Collision Dose in Rugby League: A Systematic Review, Meta-analysis, and Critical Analysis

BACKGROUND

Collisions (i.e. tackles, ball carries, and collisions) in the rugby league have the potential to increase injury risk, delay recovery, and influence individual and team performance. Understanding the collision demands of the rugby league may enable practitioners to optimise player health, recovery, and performance.

OBJECTIVE

The aim of this review was to (1) characterise the dose of collisions experienced within senior male rugby league match-play and training, (2) systematically and critically evaluate the methods used to describe the relative and absolute frequency and intensity of collisions, and (3) provide recommendations on collision monitoring.

METHODS

A systematic search of electronic databases (PubMed, SPORTDiscus, Scopus, and Web of Science) using keywords was undertaken. A meta-analysis provided a pooled mean of collision frequency or intensity metrics on comparable data sets from at least two studies.

RESULTS

Forty-three articles addressing the absolute (n) or relative collision frequency (n min^-1) or intensity of senior male rugby league collisions were included. Meta-analysis of video-based studies identified that forwards completed approximately twice the number of tackles per game than backs (n = 24.6 vs 12.8), whilst ball carry frequency remained similar between backs and forwards (n = 11.4 vs 11.2). Variable findings were observed at the subgroup level with a limited number of studies suggesting wide-running forwards, outside backs, and hit-up forwards complete similar ball carries whilst tackling frequency differed. For microtechnology, at the team level, players complete an average of 32.7 collisions per match. Limited data suggested hit-up and wide-running forwards complete the most collisions per match, when compared to adjustables and outside backs. Relative to playing time, forwards (n min^-1 = 0.44) complete a far greater frequency of collision than backs (n min^-1 = 0.16), with data suggesting hit-up forwards undertake more than adjustables, and outside backs. Studies investigating g force intensity zones utilised five unique intensity schemes with zones ranging from 2-3 g to 13-16 g. Given the disparity between device setups and zone classification systems between studies, further analyses were inappropriate. It is recommended that practitioners independently validate microtechnology against video to establish criterion validity.

CONCLUSIONS

Video- and microtechnology-based methods have been utilised to quantify collisions in the rugby league with differential collision profiles observed between forward and back positional groups, and their distinct subgroups. The ball carry demands of forwards and backs were similar, whilst tackle demands were greater for forwards than backs. Microtechnology has been used inconsistently to quantify collision frequency and intensity. Despite widespread popularity, a number of the microtechnology devices have yet to be appropriately validated. Limitations exist in using microtechnology to quantify collision intensity, including the lack of consistency and limited validation. Future directions include application of machine learning approaches to differentiate types of collisions in microtechnology datasets.

Pectoralis major ruptures during rugby league tackling - Case series with implications for tackling technique instruction

OBJECTIVES

Document the mechanism and incidence of pectoralis major ruptures in a professional rugby league cohort, and compare to any existing data.

DESIGN

Retrospective case series.

METHODS

Case series which documents 3 such injuries incurred while effecting a tackle in 3 rugby league players from the same squad (of 36) in the same season.

RESULTS

At the initial point of contact, all three players were in a similar shoulder position of outer-range abduction and horizontal abduction and subsequently it appeared their pectoralis major was torn while attempting to effect the tackle.

CONCLUSIONS

Complete tears of the pectoralis major muscle are rare but significant injuries often requiring surgical intervention to restore full function in collision sport athletes. In this same season, the organisation changed their defensive approach which may have contributed to these injuries. Each player was managed with acute surgical repair and returned to play at the same level. Suggestions are made to consider the possible training injury implications of changing tackle technique.

Automatic detection of one-on-one tackles and ruck events using microtechnology in rugby union

OBJECTIVES

To automate the detection of ruck and tackle events in rugby union using a specifically-designed algorithm based on microsensor data.

DESIGN

Cross-sectional study.

METHODS

Elite rugby union players wore microtechnology devices (Catapult, S5) during match-play. Ruck (n=125) and tackle (n=125) event data was synchronised with video footage compiled from international rugby union match-play ruck and tackle events. A specifically-designed algorithm to detect ruck and tackle events was developed using a random forest classification model. This algorithm was then validated using 8 additional international match-play datasets and video footage, with each ruck and tackle manually coded and verified if the event was correctly identified by the algorithm.

RESULTS

The classification algorithm's results indicated that all rucks and tackles were correctly identified during match-play when 79.4±9.2% and 81.0±9.3% of the random forest decision trees agreed with the video-based determination of these events. Sub-group analyses of backs and forwards yielded similar optimal confidence percentages of 79.7% and 79.1% respectively for rucks. Sub-analysis revealed backs (85.3±7.2%) produced a higher algorithm cut-off for tackles than forwards (77.7±12.2%).

CONCLUSIONS

The specifically-designed algorithm was able to detect rucks and tackles for all positions involved. For optimal results, it is recommended that practitioners use the recommended cut-off (80%) to limit false positives for match-play and training. Although this algorithm provides an improved insight into the number and type of collisions in which rugby players engage, this algorithm does not provide impact forces of these events.

Momentum and kinetic energy before the tackle in rugby union

Understanding the physical demands of a tackle in match situations is important for safe and effective training, developing equipment and research. Physical components such as momentum and kinetic energy, and it relationship to tackle outcome is not known. The aim of this study was to compare momenta between ball-carrier and tackler, level of play (elite, university and junior) and position (forwards vs. backs), and describe the relationship between ball-carrier and tackler mass, velocity and momentum and the tackle outcome. Also, report on the ball-carrier and tackler kinetic energy before contact and the estimated magnitude of impact (energy distributed between ball-carrier and tackler upon contact). Velocity over 0.5 seconds before contact was determined using a 2-dimensional scaled version of the field generated from a computer alogorithm. Body masses of players were obtained from their player profiles. Momentum and kinetic energy were subsequently calculated for 60 tackle events. Ball-carriers were heavier than the tacklers (ball-carrier 100 ± 14 kg vs. tackler 93 ± 11 kg, d = 0.52, p = 0.0041, n = 60). Ball-carriers as forwards had a significantly higher momentum than backs (forwards 563 ± 226 Kg(.)m(.)s(-1) n = 31 vs. backs 438 ± 135 Kg(.)m(.)s(-1), d = 0.63, p = 0.0012, n = 29). Tacklers dominated 57% of tackles and ball-carriers dominated 43% of tackles. Despite the ball-carrier having a mass advantage before contact more frequently than the tackler, momentum advantage and tackle dominance between the ball-carrier and tackler was proportionally similar. These findings may reflect a characteristic of the modern game of rugby where efficiently heavier players (particularly forwards) are tactically predetermined to carry the ball in contact. Key PointsFirst study to quantify momentum, kinetic energy, and magnitude of impact in rugby tackles across different levels in matches without a device attached to a player.Physical components alone, of either ball-carrier or tackler, are not good predictors of tackle dominance.The range of magnitudes of impact of injury free tackles observed in this study provides evidence for the physical tolerance of players during the tackle.

Tackle-related injury rates and nature of injuries in South African Youth Week tournament rugby union players (under-13 to under-18): an observational cohort study

OBJECTIVES

The tackle situation is most often associated with the high injury rates in rugby union. Tackle injury epidemiology in rugby union has previously been focused on senior cohorts but less is known about younger cohorts. The aim of this study was to report on the nature and rates of tackle-related injuries in South African youth rugby union players representing their provinces at national tournaments.

DESIGN

Observational cohort study.

SETTING

Four South African Youth Week tournaments (under-13 Craven Week, under-16 Grant Khomo Week, under-18 Academy Week, under-18 Craven Week).

PARTICIPANTS

Injury data were collected from 3652 youth rugby union players (population at risk) in 2011 and 2012.

OUTCOME MEASURES

Tackle-related injury severity ('time-loss' and 'medical attention'), type and location, injury rate per 1000 h (including 95% CIs). Injury rate ratios (IRR) were calculated and modelled using a Poisson regression. A χ(2) analysis was used to detect linear trends between injuries and increasing match quarters.

RESULTS

The 2012 under-13 Craven Week had a significantly greater 'time-loss' injury rate when compared with the 2012 under-18 Academy Week (IRR=4.43; 95% CI 2.13 to 9.21, p<0.05) and under-18 Craven Week (IRR=3.52; 95% CI 1.54 to 8.00, p<0.05). The Poisson regression also revealed a higher probability of 'overall' ('time-loss' and 'medical attention' combined) and 'time-loss' tackle-related injuries occurring at the under-13 Craven Week. The proportion of 'overall' and 'time-loss' injuries increased significantly with each quarter of the match when all four tournaments were combined (p<0.05).

CONCLUSIONS

There was a difference in the tackle-related injury rate between the under-13 tournament and the two under-18 tournaments, and the tackle-related injury rate was higher in the final quarter of matches. Ongoing injury surveillance is required to better interpret these findings. Injury prevention strategies targeting the tackle may only be effective once the rate and nature of injuries have been accurately determined.