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BirdsEye View

 When Roger Bannister finished under four minutes for a mile for the first time in 1954, the feat was considered nothing short of super-human. It was indeed a feat. He and his contemporaries were limited by the technology of the period; tracks were made of cinder, running shoes were made of leather, spike implements were literal nails driven through the sole of a sneaker. On top of that, Bannister was a medical school student at the time and only able to train for an hour a day. 

Since that historic event, running technology has improved dramatically, and the sport has grown in popularity; the number of athletes breaking the formerly unbreakable barrier has grown right along with it. But the sub-4 mile remained a massive challenge, the track equivalent of “summiting” Mt. Everest. In the 1960s, only 30 men in the world accomplished it; the next two decades saw 68 and 69, respectively. Track and Field News still keeps a list of every American who has run under 4:00 for a mile (I’m dating number 375). 

That list is beginning to rapidly expand. The first two months of 2023 saw more than 75 athletes break the 4-minute-mile barrier, including 52 at a single Boston track meet. That event, more than any other, raised an obvious question: What happened?

Technology happened.

In 2017, Nike unveiled a new shoe: the Vaporfly, otherwise known as the 4%. These (sort of) dorky-looking flats quickly took on the moniker “super shoes” and sparked a heated debate among professional runners that continues to this day.

Super shoe technology works by combining two existing materials — a stiff but bendable carbon fiber plate and lightweight polyamide block elastomer (PEBA) foam — in a novel way. Rather than simply slapping a plate to the bottom of a racing flat, super shoes sandwich the carbon fiber layer between two slices of foam. This “stacking” allows the shoes to bend and spring back more quickly than traditional racing flats, returning more energy to the runner with each footfall and thereby improving performance by around 4% (hence the nickname). 

After the Vaporflys hit the market, world records across distance running events started to fall. The 5k, 10k, and half marathon became a revolving door of new record holders. The women’s marathon world record, which had stood since 2003, was toppled by over a minute in 2019. That same year, Eliud Kipchoge became the first person to break 2 hours for the marathon while wearing a pair of Nike prototypes. For those who don’t want to do the math, that’s 4:34 per mile — for 26.2 miles straight. 

Professional swimming underwent a similar revolution in the mid-2000s when Speedo unveiled its LZR suit. The sharkskin-inspired fabric works by compressing the swimmer’s body while simultaneously trapping air, allowing athletes to glide through the water with 38% less drag compared to a conventional suit. This one innovation turned swimming upside down — 13 world records fell within a month of its release.

LZR’s reign reached its pinnacle at the 2008 Beijing Olympics. There, athletes wearing a full-body version of the super Speedo suits broke an astounding 25 world records. Data later revealed that 98% of swimming medalists from those Games were wearing LZR, including US legend Michael Phelps. 

The issue with LZR tech wasn’t so much that it was fast — it was that it was proprietary. Athletes competing for countries sponsored by a brand other than Speedo simply didn’t stand a chance. Ultimately, this prompted World Aquatics (formerly FINA) to put strict limits on the thickness, buoyancy and body coverage of swimsuits worn in competition. LZR wasn’t banned, but it was toned down.

When Kipchoge broke the 2-hour marathon in 2019, I was competing as a full-time professional runner. My teammates and I were getting ready to train for the 2020 Olympic Marathon trials in Atlanta, Georgia, and we had recently signed with a new shoe sponsor. Unfortunately, it wasn’t Nike. Rumors quickly began swirling that anybody racing the trials without Vaporflys was going to be at a 4% disadvantage.

In the weeks leading up to the race, numerous coaches, athletes and non-Nike shoe brands petitioned running’s governing body, World Athletics, to ban the super shoes. World Athletics eventually compromised by allowing the Vaporflys, but banning shoes that exceeded 25 millimeters in height or stacked multiple carbon fiber plates on top of one another (ruling out the Nike prototypes Kipchoge wore during his sub-2 hour marathon). These rules have since been adjusted to shoes exceeding 20 millimeters. 

So why, after all of this, are the impacts of super shoe technology just now showing up in the mile? 

Part of it is because super shoes started out as strictly road racing flats. A track version of the Vaporfly (called the Dragonfly) wasn’t developed until 2019. And thanks to COVID disruptions, the new shoes didn’t really hit the track in meaningful numbers until 2021. 

Another factor is brand competition. Since 2019, most other major running brands have debuted their own super shoes, which utilize a similar carbon-fiber-and-foam parfait structure. Some of these designs appear to be giving Nike a run for their money — which only serves to make races faster and more competitive. And then there’s the simple fact that, well, records get faster over time. A rising tide lifts all boats; as more and more talented athletes compete, they’re going to make one another better.

So, does this mean we should start mourning the 4-minute mile barrier? Personally, I don’t think so. The 4-minute mile has been held up as a gold standard partly because it’s difficult, but also because it’s a nice, round number that, at one minute per lap, is easy to wrap your head around. But it’s an arbitrary barrier. Barriers are meant to be broken.