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Newsletter - Players Matters

Players Matters - April 2024

April 2024

Instrumented mouthguards

The use of instrumented mouthguards (iMGs) represents a new era of head impact research in the sport.  Before these devices, we understood head injury risk factors by waiting for events like tackles and rucks that caused clinical signs (that is, concussions) to appear.  That happens around once every 500 tackles, working out to about twice every three matches.  It meant that we were studying what is, in effect, quite a rare event.

What iMGs allow is for every single event to ‘count’.  Every time there is a head acceleration, whether in a tackle, a ball carry, a ruck, a scrum, a lineout or a maul, the  iMG measures it, and so we can start looking at what factors are responsible for the higher ones, when the head acceleration also presents with clinical signs and players are concussed, and what the total “head load” of a player in a match, a season and even a career is.  The sample for analysis has increased from two every three matches to about three thousand events every three matches.  The player welfare value from these devices is enormous.
The first application of the devices was to incorporate them into the sport’s Head Injury Assessment process.  We can’t stress enough that this was not meant to help team and match doctors diagnose a concussion – that would, at this early stage, be a significant over-reach of the technology.  Instead, we decided that the iMG could become, in effect, a second set of eyes, technology that would help us identify when a player had experienced a very significant head acceleration event without clinical presentation, and then put that player in front of their team doctor to be assessed.

To achieve this, we identified thresholds for peak linear and angular acceleration, using three years worth of data in elite men’s and women’s rugby.  These thresholds, set at 75g for linear and 4500 rad/s2 for angular acceleration in the men’s game, corresponded to what we estimated would happen every thousandth head acceleration, and at a rate of roughly one per match.  In other words, when a player experienced a head acceleration above those thresholds, they’d just experienced a 1 in a 1000 event, which we felt should be assessed by the match and team physicians at the time, and in the days after the match.
This was first done in the WXV events last year, and then the Men’s Six Nations in February, followed soon after by Super Rugby Pacific and Aupiki.  It’s fair to say that the roll-out was not without its challenges, but we are also very pleased with how it has performed, and the value it adds to our player welfare initiatives.

For one thing, in Six Nations alone, we now have over 15,000 head accelerations to work with.  We’re five rounds into Super Rugby Pacific, and that’s provided another 30,000 head accelerations.  As expected, this is a goldmine of data that we will now begin to analyze with a view to understanding head impacts, in order to prevent them.

My team and I have been tracking these HAEs and the clinical outcomes throughout the tournaments. The figure on the left shows the Six Nations match day events, with each impact identified by its Peak Linear Acceleration (PLA, x-axis) and Peak Angular Acceleration (PAA, y-axis).

The dashed lines show the above-mentioned thresholds at 75g and 4500 rad/s2, above which the player was removed for an HIA1 screen.  In the 15-match tournament, this happened 13 times, once every 1200 head accelerations.  In Super Rugby Pacific, it has occurred 26 times in 30 matches, every 935th impact. 


For now, as mentioned, we want to avoid diving too deeply into the diagnostic performance of the iMG in the HIA process, because it is not intended to diagnose a concussion.  However, we are cautiously optimistic about the real value it is already adding to the HIA process.  Between Six Nations and Super Rugby, we have identified a number of concussions in players who did not show up with clinical signs at the time of the head impact, and who might, were it not for the iMG alert, played on and never been diagnosed.  

Players were also removed from play after their HIA1 screens, done solely on the basis of an iMG alert.  We believe this is conservative and necessary.  Previously, we would have been reliant on these players showing up with symptoms after the game.  If nothing else, our ability to identify these cases much earlier represents player welfare progress.

As mentioned, the onboarding of tournaments continues apace, with the Women’s Six Nations two weeks in, and Major League Rugby in the USA at its five week mark.   The early work analyzing these tens of thousands of head impacts has also begun.

I want to also highlight a very important lesson that we learned in the rollout of the iMG as part of the HIA process, as it is something we need to be constantly mindful of. Our intention is obviously player welfare, but we recognize and respect that an initiative like this is going to have real-life impacts on players, because the iMG alert is a signal to remove a player for a screen, and possibly for the rest of the match.  This is why we chose the thresholds to be as high as they are – any lower, and we would risk excessive disruption of the match, alienating coaches and players and undermining confidence in player welfare.

It also means that we must respect the voice of players and coaches when they provide feedback to us.  These people may fully support player welfare tools and interventions, but they do also have incentives for performance, and the desire to have their best players on the field (coaches), and to continue playing (players).  Out of respect for them, we cannot be blasé or excessive in our use of such tools.

One such example was that the premise of the iMG alert was that it would be instantly seen by the Match Day Doctor, who would then ask for the player to be removed for an HIA1.  But, for technical reasons related to getting the Bluetooth signal from the iMG to the MDD’s iPad, this was occasionally delayed.  This led, understandably to some confusion, and eventually, mistrust of the iMG by players and coaches.

We heard these concerns, and held a number of very honest, frank, and ultimately constructive meetings that led to a change in the process of iMG alert driving testing.  Instead of every iMG alerting indicating that a player should be removed for an HIA1, a compromise was reached where players with iMG alerts would be assessed by their doctors on the field, and if the player appeared normal, the HIA1 screen could be delayed until either half-time or full-time.  This was a change we agreed with our Independent Concussion Working Group, and which was intended to alleviate pressure on the match day and team doctors, and to facilitate greater compliance and confidence in the system.

We are always mindful that our welfare interventions are reliant on good, effective implementation, and this requires that our primary stakeholders – coaches, players and the team doctors – be fully onboard.  Valuable lessons have been learned through the first two months of this project, and we are open to learning many more, because the reward and benefit to be gained is too large for us to tolerate failure and rejection of this invaluable tool.

Brain Health Services

We're thrilled to announce the launch of the World Rugby Brain Health Services in partnership with players associations RPI (Rugby Players Ireland) and RUPA (Rugby Union Players Australia). This groundbreaking service is now available in Ireland and Australia, offering retired professional players a comprehensive screening process designed to promote brain health and overall well-being. 

The Brain Health Services consists of three distinct stages:

Stage One: Self-Assessment Questionnaire: Players complete a detailed questionnaire covering various aspects of their life, including medical history, sports participation, daily habits, and screenings for anxiety and depression.

Stage Two: Cognitive Assessment: Following the questionnaire, players are paired with a trained Brain Health Practitioner in their country who guides them through an online cognitive assessment comprising 11 tests to evaluate cognition and memory function.

Stage Three: Report and Recommendations: Once completed, the player's report is sent to their designated Family Medical Practitioner for review and further recommendations or specialist referrals.

Additionally, it's important to note that the Brain Health Services serve as an educational tool, providing players with valuable insights into their overall health beyond just cognition. By assessing various aspects of their well-being, the service aims to empower players to take proactive steps towards optimising their brain health and overall quality of life.

Over the coming months, our aim is to expand the reach of these services to include other countries, and to promote their use in support of retired players. For those interested in learning more about the Brain Health Services or exploring implementation within their region, please contact Deirdre Keating at


Player Welfare & Laws Symposium

We recently concluded a successful series of online webinars in early April, covering topics such as the Shape of the Game, Instrumented Mouthguards, Safety vs. Spectacle, Heat Guidelines, and Brain Health Services. All presentations and recordings are now accessible on the Player Welfare Website at

Thank you for reading.

Prof Éanna Falvey