The science behind GAA refereeing

By John Harrington

When first contact was made with Aidan Brady to arrange an interview about his work tracking the fitness of inter-county referees, his immediate response was typical of a sports scientist.

He requested a list of questions that would likely be asked to ensure he could come fully armed with all the relevant information.

Like everyone else in his field, Brady is a statistics fiend. Someone who trades in cold, hard facts and proof rather than conjecture.

He completed an undergraduate degree in 2016 in Sports Science in the School of Health and Human Performance in DCU and for the past three years has been overseeing the fitness of inter-county referees and gathering data.

He’s also two years into a four-year PhD in DCU under the supervision of Professor Niall Moyna who has worked with the GAA inter-county referees for over a decade. His work is funded by the GAA and the Irish Research Council, and is focused on understanding the physical demands of the game and the fitness levels required to officiate at the highest level, with the ultimate aim of improving decision making.

No one can dispute the fact that the speed of inter-county football and hurling has increased significantly over the last couple of years and Brady is helping to ensure that inter-county referees are keeping pace.

“To date, we have collected GPS data from 685 inter-county games which includes all of the games from the senior Championships over the last 4 years," Brady told GAA.ie.

“From the GPS data that we collected between 2017 and 2018, we saw a significant increase in the volume of high-speed running that referees were doing.

“In hurling, we had an increase of almost 50% in 2018 in the amount of high-speed running compared to 2017 and a 16% increase in the number of sprints which now average 49 per game”.

“From a fatigue point of view we have not seen a decline in total distance or high-speed running in the second-half compared to the first which reflects the high standard of physical fitness of the referees.”

To back up that point, Brady opens a note-book full of statistics that outlines just how fit the average inter-county referee is today.

The GPS data that has been collected for the past four years shows that inter-county referees are covering an average of 9.5 kilometres per match.

That works out as an average of 135 metres per minute which compares very favourably with professional soccer and rugby referees.

A 2011 study of Premier League referees showed they covered 125 metres per minute while a 2019 study in rugby union showed they covered 85 metres per minute.

“If you take into account the size of the pitch, Old Trafford is approximately 105 metres in length and 70 metres in width and by comparison Croke Park is approximately 145 by 90 metres so you have five or six thousand square metres of extra ground which they have to account for," said Brady. "There's a big difference between the two”.

“A study published in 2018 on senior inter-county hurlers showed that, on average, they cover 7.6 kilometres whilst a 2017 study showed that inter-county footballers cover on average 8.8 kilometres per game.

“From a total distance point of view the referees are covering more ground. Obviously, players are doing more high-intensity, top-end work but it shows the volume of work the referees have to get through during a game while also making all of their decisions.

“In the same studies the top speed reached in games by inter-county players was shown to be on average just over 30km/h.

“We’ve now seen referees reach speeds just under 29 km/h in the football Championship and just under 28 km/h in the hurling Championship”.

“While referees are slightly older than the average inter-county player they still have that explosive speed and endurance”.

“We are now developing a number of machine learning algorithms in conjunction with Dr. Andrew McCarren in the School of Computing in DCU to better understand the physical demands placed on referees”.

In early October a 12-15 week plan, consisting of three sessions per week, commences for all inter-county referees in preparation for the national league.

This brings them right through to January when the national panel are required to pass the ‘Yo-Yo intermittent recovery test’ if they want to officiate during the national league.

The Yo-Yo test is a measure of endurance capacity. It consists of a series of intermittent shuttle runs, 20 metres forward and 20 metres back with a ten second break in between. The time you have to complete the run gets progressively shorter as the levels increase. The current pass-mark for the national league is 16.8 and 17.4 for the Championship fitness test.

The average referee’s score for the Championship test this year was 18.1 which equates to 44 shuttle runs while the highest score was 19.7 which is 58 shuttle runs.

Anyone who has endured the lung-shredding torture of a Yo-Yo test will appreciate just how good a score of 19.7 really is.

The Championship panel of referees convene in the GAA’s National Games Development Centre in Abbotstown for regular collective fitness sessions during the Championship.

The fitness sessions are followed by a debrief in which the referees review recent matches where their decisions are analysed and critiqued.

Lactic acid in the blood is a good indicator of the intensity of effort being put in by referees during a game. A high level of lactic acid in the blood may impede a referee’s ability to perform repeated sprints throughout the game.

In order to measure the levels of lactic acid, Brady takes a blood sample from the referees before, at half time and after the game.

During the year, referees also visit the high-performance lab in DCU’s School of Health and Human Performance where they have an ECG to check their heart and undergo a VO2 max test which is regarded as the gold-standard measure of cardiorespiratory fitness.

Every referee on the inter-county panel has scored in the top five per cent for their age-group.

A high level of fitness obviously isn’t the only tool you need in your locker to be a referee of the highest quality, but Brady is adamant that it definitely helps.

“Obviously refereeing is about decision-making, but if they don't have the fitness to keep up with the play then how can they be in the right spot to make the right decision”.

“We know from previous research that physical fatigue directly affects cognitive performance. Your ability to think, react and concentrate on what is happening in front of you are all affected by physical fatigue so this is why fitness is so important”.

“This is reflected a lot in the heart rate data which we collect alongside the GPS. Take for example James Owens and the crucial decision he had to make in the All-Ireland Final.

“We looked at his heart-rate data from that and it was amazing how composed and steady it was. I have watched it back a number of times and his composure and his ability to take his time, relax himself and make a calm decision in such pressurised circumstances was extraordinary.

“For most people, in this situation, heart rate would spike massively because of the combination of sprinting and anxiety but this is what the best referees do really well. They can recover quickly and bring their heart rate back down to make a composed decision. This comes from their high level of fitness and years of experience”.

In much the same way that inter-county players are constantly pushing to be the best they can be, so also are inter-county referees.

Brady and the referees put in a lot of hard work together, and he has found that they’re always looking for more ideas and sessions from him rather than being resistant to the increasing level of analysis of their physical and mental capacity to referee at the highest level.

“I think they've really relished the challenges and have taken all of the feedback on board” said Brady.

“When we first gave them the GPS reports back in 2016 it was a real eye-opener for them. After that I think their interest really increased and they have all bought into what we are trying to achieve as a group”.

“They're not only now looking at their refereeing from a decision-making point of view, but they're looking at it from a physical standpoint also. They're analysing their own performance and then asking, 'how can I get better’?”.

“The referees now expect the GPS on game days because they want the information and the feedback that comes with it. It's about trying to get that extra edge to help make them as good as they can possibly be. The referees have put in a huge effort and the commitment they give to all aspects of their performance is massive.

“They all have jobs and families and a life outside of refereeing but refereeing is a large part of their lives. Some of them may have to travel from as far away as Cork, Donegal, or Mayo up to Abbotstown, that’s at least two or three hours in a car for an hour long fitness session and an hour and a half or two-hour review and the same on the return journey.

“That means leaving work at five o'clock and maybe not getting home until one or two in the morning regularly for three or four months. It’s a huge commitment and I don't think it quite gets the recognition it deserves”.

Brady might be a scientist who likes crunching numbers and extrapolating statistics, but over the course of the last few years he’s also naturally developed a bond with the referees he’s trained.

He knows just how much they’ve sacrificed to be the best they can be, and can’t help but wonder if criticism of their decisions would be less caustic if everyone knew the work they’re doing behind the scenes.

“At the end of the day they go home to their families and back to their normal lives after a match,” said Brady.

“At times, the criticism can be extremely harsh but I think they know getting into it that this level of scrutiny is part and parcel of the job. Every game is competitive. You've got thirty players on the pitch who all really want to win and there is one individual in the middle of the park trying to keep the game played in as fair a manner as possible. It’s a very difficult job and no matter what they do they're going to be scrutinised”.

“I do think, though, the inner workings of refereeing, what really goes on, if a bit more light could get be shed on how hard they work I think people may be a little less critical.

“Refereeing is a hell of a lot harder than it looks and they only get a split second to make a decision. As spectators, we get the chance to see things from multiple angles and we have time to sit back and say do I think that's right, do I think it's wrong, and people still disagree after seeing all of that.

“I think the work that they do and the preparation that goes into it, should get a little bit more positive attention because it's a tough job and it's a big commitment and no referee goes out onto the pitch wanting to make a mistake.

“So, why be a referee you asked? If you talk to any of them they will tell you they do it because they love the games and they love refereeing.

“They would say where else would you want to be on All-Ireland Final day than in Croke Park!”