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Yellow sliotars will be used in the 2020 All Ireland Hurling Championship.
Yellow sliotars will be used in the 2020 All Ireland Hurling Championship.

The science behind the yellow sliotar


By John Harrington

The GAA’s decision to replace the traditional white sliotar with a yellow one for this year’s Championship has sparked a strong reaction in some quarters.

Much of this seems to have been founded on the misguided belief that the yellow sliotar would perform differently to officially approved white sliotars that inter-county players have previously used.

That is simply not the case. The only difference between the sliotar that will be used in this year’s championship and last year’s championship is the colour.

The officially approved yellow sliotars are identical in composition, size, and weight as the officially approved white sliotars produced by the same suppliers which have been used in the All-Ireland Championship in recent years.

But, why move from a white sliotar to a yellow sliotar at all?

The decision was made for the benefit of both players and spectators alike and is based on rock-solid science.

As part of the research that was done before making the decision to move from white sliotars to yellow sliotars, the GAA consulted with optometrist Valerie Kennelly who is considered a world leader in the field of Sports Vision.

In fact, the subject matter of her Masters of Philosophy in Sports Vision was ‘The visual skills of Gaelic Footballers’.

Valerie Kennelly, an Optometrist who is a world leading authority on sports vision, pictured speaking during the 2014 GAA Coaching Development Conference. 
Valerie Kennelly, an Optometrist who is a world leading authority on sports vision, pictured speaking during the 2014 GAA Coaching Development Conference. 

The reason she recommended that the GAA move from a white sliotar to a yellow one couldn’t be simpler – it’s much easier to see the yellow ball, especially in the sort of conditions that hurling is commonly played in.

“An object viewed against a contrasting background is easier to see,” explains Kennelly. “In a normal eye-test you're looking at black letters on a white background.

“You'll be able to see a small white ball if your vision is good under good conditions, so against a blue sky.

“Whereas when the contrast is poor, for example a grey letter against a white background or a white ball against a cloudy sky, then it's contrast sensitivity that we're talking about and everybody will be affected by poor contrast.

“So, if you're looking at a white ball against a cloudy sky then everyone in a stadium will have difficulty seeing a white ball against a grey sky even if they have really good vision.

“The elderly and people with underlying conditions will sometimes find it even more difficult than everyone else.

“Met Eireann has said that Irish skies are completely covered by cloud for well over 50 per cent of the time.

“That's due to our geographic position off the north west of Europe closer to the path of the Atlantic low pressure system which tends to keep us under cloudy airflows for much of the time.

“A yellow ball against a grey sky is much easier to identify, and not just for the players.”

Many people will object to a yellow sliotar on grounds of tradition.

Hurling has been played with a white sliotar for so long that the thoughts of moving away from that will be anathema for some.

The same debate flared when tennis moved from white balls to yellow balls, but that decision was made with good reason too.

“The International Tennis Federation wised up to this way back in 1972,” says Kennelly.

“They conducted research for television viewers when their televisions went from black and white to colour, and they realised that a white tennis ball was very difficult for TV viewers to watch and that a yellow ball would be the best colour to use for TV viewers.

“The same is true for viewers who are actually watching a sport in the stadium and for the players too. Wimbledon tried to hold out using the white ball for tradition until 1986 when they eventually had to bow under pressure because the viewers watching Wimbledon were finding it much more difficult to see the ball when it was white. So, in 1986 the white ball was changed to a yellow ball.

"It's exactly the same for hurling and camogie. Tennis and camogie are very comparable when you compare the size of the ball and the conditions they play in.

“But particularly because hurling and camogie are Irish sports played in Ireland and 50 per cent of the time we're competing with cloudy conditions, it's a no-brainer.

Tennis changed from white to yellow balls because they were easier to see for players and spectators. 
Tennis changed from white to yellow balls because they were easier to see for players and spectators. 

“We have to change to the yellow ball and doing so will make it easier for everybody.”

Club and county GAA teams have put a lot of effort and no little expense into improving their level by focusing on gains in the areas of strength and conditioning and skill-specific training.

Kennelly believes they would be well advised to also focus on the significant performance gains that could be made if they took an interest in the visual ability of their players.

Her studies have shown that the development of many players is limited by visual defects that have either not been diagnosed or treated or both.

“I've spoken to a lot of managers, and a lot of them would say, 'Oh my God, I can't believe we didn't think of this before'”, she says.

“It's kind of like the elephant in the room. It's so obvious that people think it can't really be that important. But when the penny drops you'll have people say to you, 'Oh my God, why didn't we think of this'. But then they often don't follow it up the way they should.

“And I think it's because on the one hand it's so obvious that they think surely a player would know themselves, but they don't. There's very little take up. Even for international sports, there's very little awareness around the importance of vision.

“There really needs to be a big educational campaign, I think, to bring that to people's awareness really.

“When I did a Masters in Sports Vision I looked at the visual skills required to play hurling and football and different aspects of vision. So not just your ability to see black letters on a white chart.

“I looked at eye-movement and muscle reliability. So, if there was any muscle deficiency, how would it affect a player's ability to play sport.

“A lot of times players think their vision is okay and they can see the ball with no problems, but they may not be aware that their eyes are not working together optimally, that there might be a small deficiency that's affecting their accuracy.

“Sometimes that might only show up when someone is dehydrated or under stress, under normal conditions they might be fine. But during a thorough sports vision assessment you can see if they have any underlying problems that could make a difference between performing to their best and under-performing.

“A lot time people won't really pay too much attention if one eye isn't as good as the other eye because they feel the other eye is doing what it needs to and that's good enough. But it's not good enough when you're dealing with sport at inter-county level.

“But even at club level, if you want to be the best you can be then you have to start with your visual system and get that up to scratch. Everything else is secondary to that.

“It doesn't matter what sort of strength and conditioning and skill training you do, if your vision is wrong then you're never going to perform to your best.”

Kennelly’s studies have proven that someone who is colour-blind is highly unlikely to make the grade as an inter-county footballer and hurler.

Someone with red-green colour blindness would struggle to differentiate the Cork and Limerick jersies. 
Someone with red-green colour blindness would struggle to differentiate the Cork and Limerick jersies. 

But it’s also an issue she believes could be remedied with a simple solution.

“In normal conditions, the vision of eight per cent of men is red-green colour deficient, which means that one in twelve men can't identify the difference between red and green.

“If you look at the jersies for the county teams, 14 out of 34 jersies are either red, green, or have both colours in them.

“At county level, less than 1 per cent of the players I tested were colour deficient. Whereas at club level seven per cent of the men that I tested were colour deficient.

“Which suggests that if you're colour-blind it makes it much harder to reach the level required to be an inter-county footballer.

“Every other aspect of your game might be perfect, but if you can't differentiate between a team-mate and an opponent quickly and easily, then that's having a negative effect on your ability to reach that level.

"For the same reasoncertain percentage of the male viewers watching a match can't identify the different jersies when they're up against each other.

“That's something I think the GAA should really consider looking at. Because there are clever ways that you can adjust the colour of a jersey so that it won't affect either players or spectators.

“Say, for example, if Cork were playing Kerry. Cork are red and white and Kerry are green and gold. If Cork were wearing a jersey that was predominantly red and Kerry were wearing a jersey that was predominantly green, that's going to be a big challenge for the players and viewers watching that match.

“But if Cork played in a predominantly white jersey with red stripes, or the Kerry jersey was predominantly yellow with a bit of green, then there would be no conflict. It would be so easy for eight per cent of the men watching the match and it would be easier for players that might be colour deficient to reach inter-county standard too.

“No more than in pool where they added spots and stripes to balls to make it easier for those with colour-blindedness to identify the balls.”

Inter-county hurlers don't just see better than average, they see differently than most people too. 
Inter-county hurlers don't just see better than average, they see differently than most people too. 

It turns out the inter-county footballers and hurlers don’t just have better vision than the average populace, they also see things differently

About 80 per cent of the population are right-eye dominant, right-handed, and right-footed or else left-eye dominant, left-handed and left-footed. Leaving 20 per cent of the population to be cross-dominant which means either right handed but left-eye dominant, or left-handed but right-eye dominant.

But when Kennelly analysed elite Gaelic Footballers and Hurlers, she discovered a much higher percentage were cross-dominant.

“When I was testing in Ballyboden St. Enda's I tested about 30 people and there was a high percentage of people that were cross-dominant.

“And when I was speaking to the manager afterwards he asked me which players were cross-dominant. 10 of their squad were on the Dublin panel, and every single one of those players were cross-dominant, which I thought was remarkable.

“I was then giving talks to hurling coaches and managers and almost every single one of them that was coaching or managing a hurling team was cross-dominant.

“And when you think about it, when you're playing hurling it's different to football you're holding the hurl in your dominant hand and then you're catching the ball in your opposite hand and it's easier to catch a ball if it's in line with your dominant eye.

“And it's also easier to score a goal if it's the dominant eye that's looking at the goal. Because your non-dominant eye will see the goal in a slightly different position.

“So even though you'll see the goal perfectly clearly, the location of the goal will be altered if you're looking at it with the non-dominant eye.

“What we don't know is have those players reached the top because they were cross-dominant, or did they become cross-dominant because they were playing hurling? That would be a really, really interesting study.”

Kennelly’s bottom line is a simple one. The better you can see a sliotar the better a hurler you can be and the more enjoyable an experience watching a match will be for the spectator.

The move from a white sliotar to a yellow one will never sit well with those who prefer to see tradition maintained, but the science behind the decision is indisputable.