Analysing the Trionda: The science behind the 2026 World Cup ball

The ball is a defining feature of every World Cup. It's the game's equivalent of the artist's paintbrush or the musician's instrument, designed for the best players to perform and to catch the eye of those watching -- in the stadium and elsewhere. "Every single ball is different," says Andy Harland, a professor at Loughborough University in England who has tested Adidas' major tournament footballs ever since the 2002 World Cup, "and there's no such thing as the perfect flight of a ball. It's subjective." Harland spends the better part of an hour on a video call with The Athletic to talk through one fundamental question: what's the science behind a World Cup football? Adidas says that three-and-a-half years of work and around 300 lab tests went into the Trionda ball. It contains a chip which helps with semi-automated offside calls, as well as determining who last touched it. Like all modern balls, the outer layer is polyurethane and the inner is a mix of materials (primarily polyester), inside which the bladder is located -- that's the bit that gets inflated. Notably, the Trionda consists of only four panels, which are thermally bonded together. It's the fewest panels ever for a World Cup ball and five times fewer than the version used at the previous edition of the tournament in 2022. When The Athletic took a selection of footballs to Loughborough last May for testing, we spoke to Ieuan Phillips. He's a researcher there and a colleague of Harland, and carried out research on the Qatar 2022 ball. Phillips has a huge trolley of 30 footballs from different eras that he has analysed to understand their differences. "Adidas' 2004 Roteiro was the first ball that went from being hand-stitched to being thermally bonded," he said. "It took basically the same panel design. It's got an inner carcass, so a woven layer around the bladder onto which the panels are thermally-bonded, which allows no stitching because it's all glued as one piece." Harland offers some reasons as to why a ball might be designed with fewer panels, with the caveat that he and Phillips just test the balls -- it's Adidas that creates them. "The smaller number of panels, generally speaking, lowers the assembly costs," he says. Something called 'mould tooling' is needed for all the panel shapes and component parts, so more and different pieces require greater materials. "With more straightforward production and more straightforward assembly comes greater reliability, so there are going to be those advantages. Every ball is, give or take, the same now. It's not like it was back in the handmade days, when there were big discrepancies between balls." Harland contrasted this year's ball to the one produced for the 1970 tournament in Mexico, the first time Adidas created a bespoke ball for a World Cup. The iconic Telstar design, made of leather, it took hours to craft. "We had, of its day, probably the world's most-advanced 32-panel hand-stitched soccer ball used on the elite level," Harland says. Twelve of the panels were black pentagons, to make the spin of the ball visible for the TV audience. "The champagne colour and the coloured graphics... I still meet people who say it was their favourite ball," he adds. So what's changed in half a century since? Materials and manufacturing have improved, leading to "cheaper and faster (manufacturing) and higher quality controls," Harland explains. Because panels are custom-designed, there's much more creative licence, which helps explain the switch from a 20-panel ball four years ago to a four-panel one this time. "The specifics of this tournament, which has games played at sea level and at altitude, mean that there's an added complication," says Harland. The highest stadium is Estadio Azteca in Mexico at 2,200m (7,218ft), which provides aerodynamic challenges in addition to physiological ones. At higher altitudes, balls tend to fly straighter and curve less. That, of course, was shown at the 2010 World Cup in South Africa, where the Jabulani grabbed headlines for its erratic and unpredictable movement -- so much so that there's a Wikipedia page dedicated to its criticisms. Simulation tests by Austrian researchers the same year as that tournament predicted that the combination of the Jabulani ball and altitude could have "a major effect" on shots and direct free kicks. By their models, a ball launched at the same speed, angle and trajectory for a top-corner free kick in Durban (sea level) would not go in at six of the other nine South African stadiums at higher altitudes. "Jabulani was the first ball that featured the grooves in the panels," Harland explains. "If you compare how many grooves that design had and the dimensions of those grooves with where we are now, then, for good or for bad, the decision has been to make the balls considerably rougher." The smoothness of the Jabulani was considered to be a cause of its wobbliness in flight. "There's no value in re-opening the Jabulani debate," Harland says, but adds that "you need a certain amount of what we would call roughness -- what the general public would recognise as being seams". He explains that it's an oversimplification to equate roughness with drag (resistance) and rather about ensuring the ball flies more consistently and predictably. "At different speeds, the ball will have a very different drag," he adds, typically being higher at lower speeds. These principles are how, mathematically, they can provide an explanation for dipping shots: balls start to decelerate as soon as they are kicked, slowly at first and then rapidly once it transitions from a smooth into a rough flow state, which is when the drag increases. "It's not dipping necessarily, it's just slowing down and gravity is having a more noticeable effect." Panic not, though, about any Jabulani-esque goals in Mexico over the coming weeks. Adidas, in its press release announcing the ball last October, said it has added "intentionally deep seams" and "strategically-placed debossed lines" into the ball to ensure the drag is "sufficient and evenly distributed", thus guaranteeing stable flight. Designers Solene Stoermann and Hannes Schaefke told VERSUS that they tested the ball in seven of the tournament's 16 host cities to check its versatility. "This ball has no alarms associated with it," Harland says. He first saw it "a couple of years ago" as a plain-white ball, which is typical of how they receive prototypes. How did it perform? "It's not at any extremes. It's not the fastest, not the slowest. It's a ball that evolved from all the learnings in lots of different aspects," he says, adding that minor changes to the final version could have been made after they tested it. At its HQ in Germany, Adidas has replicated the kicking robot which Loughborough created in 2006, so most of the work at the university these days is done in the wind tunnel. "We have a test routine that we go through," Harland says. "We look at changing all the flow speeds. We call it 'sweeps', from low to high speeds, and then we'll sweep from high to low speeds sometimes. We do a yaw sweep. That means we position the ball at different orientations towards the flow to make sure that there aren't any particular orientations that are unbalanced, and we'll do some spin tests to look at the side forces." All this gets calculated, charted and sent to Adidas. Exactly what they are testing for, Harland explains, could be anything: "phenomena, concepts, even sometimes thoughts or questions, hypotheses, characterised by (someone saying), 'We don't currently have a way of measuring this. We think it might be a feature of the ball or something that we want to control for'." They also do some mechanical testing, having developed procedures in-house over multiple decades. "Most of them are now being done at Adidas," Harland says. Some of those are similar to the Quality Programme for Footballs that FIFA introduced in 1996. That eight-step process analyses balls according to eight criteria, including circumference, water absorption, rebound height, shape and size retention, and sphericity (a measurement of roundness). They have standards with upper and lower boundaries. So long as the ball lands between those, it can be designed however. "I dare say if the very first soccer ball that was produced was perfectly spherical and perfectly smooth, the game would have been a farce and it wouldn't have taken off," Harland says with a chuckle. "It was the fact that the ball naturally behaved itself in the air in a predictable way -- a little bit like the evolution of golf balls from smooth to dimpled." The only thing Harland can't provide a good answer for is just how many balls he and fellow researchers have tested at Loughborough. But this is men's World Cup ball number seven they have been involved with. "I know that I am under quite considerable pressure from my technical colleague, who has pretty much given me the final ultimatum to clear the store cupboard out," he says, half laughing and half serious. "Because a lot of the balls that we have tested are one-off prototypes, some have unique value to them, and we've managed to put those away. But then you've got the disposal of these things -- they can't just go in the domestic waste." He reckons the number of ball models is in the hundreds, and into the thousands for total balls. "Because we've had at least one, but normally two, soccer ball research programmes running at any one time. "We're quite good at this in the sense that we've been doing it for a while now. We're pretty confident that, if Adidas or another brand wanted to supply us with an example ball, we could position that ball within other tournament balls -- probably if you just give us one, right? If you want to be doubly certain, then give us two, and we'll confirm that they're the same."