This weekend, 28–year–old Josh Kerr ran a mile in just three minutes and 42.66 seconds, smashing a record that has stood almost as long as he has been alive.
In a stunning performance at the World Athletics Diamond League competition, Kerr shaved nearly half a second off the mile record set by Hicham El Guerrouj in 1999.
So, what was the key to Kerr’s incredible success?
According to experts, the secret lies in his shoes, clothes, and naturally strong stature.
Kerr ran his record–breaking race in a pair of one–of–a–kind supershoes that were specially designed for his feet and running style.
Dubbed the Brooks Hyperion 222, these unique shoes feature a unique profile for an ‘ultra–aggressive’ ride alongside extra–stiff carbon plates and lightweight titanium pins.
During the race, Kerr also sported a ‘speed suit’ shaped to his body and covered with tiny ‘laser cut perforations’ to boost cooling and aerodynamics.
However, none of this would matter if it weren’t for Kerr’s above–average size and strength that allow him to make the most of this new technology.
Kerr ran his record–breaking race in a pair of one–of–a–kind supershoes that were specially designed for his feet and running style
In a stunning performance at the IAAF Diamond League athletics competition, Kerr shaved nearly half a second off the mile record set by Hicham El Guerrouj in 1999
Since the mile record was set over 27 years ago, only one person has even come within a second of matching Hicham El Guerrouj’s record of 3:43.13.
However, the Scottish five–time global medallist didn’t just surpass this seemingly untouchable target; he shattered it.
Kerr shaved over 2.6 seconds off his previous personal best to set a new world record that could stand for many more years to come.
While this wouldn’t have been possible without Kerr’s own athleticism, experts say that he had a serious helping hand from cutting–edge technology.
Dr Brian Hanley, an expert on athletics biomechanics from Leeds Beckett University, told the Daily Mail: ‘I think the shoes contributed considerably towards breaking the record, although it is difficult to put a value on this.
‘The shoes are the interface between the athlete and the ground and the less energy is lost during each of those interactions, the better.
‘In their scientific quest to break a long–standing World Record by a legend of the sport, the Brooks team were hugely successful in combining scientific and technological know–how with the specific needs of an exceptional British athlete.’
According to Dr Hanley, the most important part of the supershoe is the stiff carbon plate embedded in the sole.
Kerr ran his record–breaking race in a pair of custom one–of–a–kind supershoes, dubbed the Brooks Hyperion 222, that had been designed for his specific feet and running style
These act like a tiny springboard, ensuring that more energy is returned into the runner’s stride with each step.
That means that more of the power generated by the athlete’s muscles goes into moving them forward, so that they can run faster for longer.
Carbon plates are the same type of technology that controversially helped Sabastian Sawe to shatter the sub–2–hour marathon limit in London earlier this year.
Dr Hanley points out that this is especially important for racing spikes since ‘the thickness of the sole is only allowed to a maximum height of 20 millimetres under World Athletics rules, half of what is allowed in road racing.’
To boost these benefits even further, the shoe is built with an aggressive curved profile shaped to mimic the bottom of a bike tyre.
For a jogger or long–distance runner, that profile would actually make running harder, but for a middle–distance runner up on their toes it helps drive their power forward even more efficiently.
Danny Orr, senior director of product development at Brooks, told Popular Science that this creates an effect ‘almost like he’s running slightly downhill’.
Mr Orr explained that this shape was chosen after eight years spent measuring Kerr’s performance and running style and was designed specifically with a record–breaking race in mind.
Kerr also wore a specially designed speed suit featuring tiny ‘laser cut perforations’ to boost cooling and aerodynamics
Unlike most races where a runner is adjusting their pace tactically to just stay ahead of the competition, a record attempt means going flat out from the very start.
That means Kerr needed a shoe that could help him maintain an average speed of about 16 miles per hour (27 km/h) for the whole race, completing each lap in about 55 seconds.
‘The notion of running slowly, or the notion of changing gears or speeding up, they’re going to feel awful in this shoe. It’s just not designed to do that,’ says Mr Orr.
‘It really is a weapon for him to run four laps at a really high speed and a really high cadence.’
The final technological flourish comes from the speed suit which Kerr wore while racing.
Brooks says that this has been ‘crafted to enhance aerodynamics and breathability, with laser cut perforations that release heat and humidity while enhancing mobility’.
Dr Barney Wainwright, an expert on sports performance from Leeds Beckett University, told the Daily Mail: ‘Drag, the force that a runner has to push against, increases with speed, and the longer that a runner is running at a high pace, the more benefit can be gained from even small reductions in the drag force.
‘At Kerr’s target race speed, approximately 10 per cent of his total energy expenditure will have been used to overcome the drag forces.
Experts say that Kerr could only get the most out of his supershoes because of his above–average size and weight, which allows him to generate more power per stride than most athletes
‘If this could have been reduced even a few percent by his specially designed clothing, his speed will have increased sufficiently to reduce his mile time by up to 0.5 second.’
However, none of these technological advantages would mean much if it wasn’t for Kerr’s unique physiology.
Kerr is somewhat larger and stronger than the average middle–distance runner, standing at six feet two inches and weighing around 154lbs (70kg), according to his data from the 2024 European Athletics Championship.
By comparison, Hicham El Guerrouj stood at just five feet nine inches and weighed only 127lbs (58kg) in his prime.
While that means he has more weight to carry, this also means that Kerr can generate more power with every stride than most other runners.
Dr Hanley says: ‘How fast an athlete can run depends mostly on how much force they can apply to the ground during each step, so if Josh can apply more force because he is stronger, this gives him a large advantage.
‘Brooks also seems to have designed the spikes to take advantage of this greater strength by making the shoe stiffer than normal.’
Likewise, experts point out that Kerr has a ‘near–perfect’ build for running.
Ker also has a large chest and well–trained heart and lungs that enable him to fuel his muscles with oxygen and remove waste gases fast enough to keep operating under extreme stress
Dr Mark Burnley, a leading expert on sports performance from Loughborough University, told the Daily Mail: ‘Physiologically, he needs a very big “aerobic engine”, or maximal oxygen uptake, to sustain 26 km/h (16 mph) for just over 222 seconds.
‘He is likely to have a large chest containing an extremely well–trained heart and large lungs.
‘This requires very high rates of ventilation to work effectively, and while the lungs cannot be trained themselves, you can train the respiratory muscles so that they don’t fatigue so quickly.’
While supershoes and aerodynamic suits might offer a small advantage, Dr Burnley believes that these physiological factors are ‘first and foremost’ what made Kerr’s record–breaking race a possibility.
Dr Burnley says that his success comes from ‘a combination of genes, training and an element of luck’.
How Nike’s £240 Vaporfly sparked the super shoe debate at the 2016 Olympic marathon in Rio
The debate of super shoes isn’t new and first reared its head in 2016, with Nike’s £240 Vaporfly product raising concern among commentators and experts alike.
During the 2016 Olympic marathon in Rio, all three male medallists wore a prototype of the trainer, with the same technology extended to track races from 2018.
The debate of super shoes isn’t new and first reared its head in 2016, with Nike’s £240 Vaporfly product
Now the high–tech trainers, which are lighter and more responsive, are ‘almost ubiquitous on the feet of elite road runners’.
That is according to Jonathan Taylor, a sports researcher at Teesside University, who has branded the revolution in footwear development a ‘technological arms race’.
Experts predicted the shoe improved the running economy of highly trained runners by four per cent compared to a normal shoe, boosting performance by three per cent.
Since 2016 when the Vaporfly was released, the top 50 male marathon runners have improved by about two per cent on average, much of which attributed to the carbon fibre plate.
Similar technology was then transferred into track spikes in 2019 which led to middle– and long–distant records falling.
Regulations were introduced in January 2020 over the sole thickness of track spikes used in sports other than high jump and long jump.
This was due to other companies replicating their carbon–fibre plate and springy foam technology into more spikes for running shoes.
The new regulations require a maximum sole thickness of 20mm for up to 400m races and 25mm for any longer distances.
However, experts say this is far too lenient, suggesting rules should be stricter and to a point where air pods can’t be inserted into the spikes.
