This is Eliud Kipchoge. The first man in history to run a marathon in under 2 hours. He did this wearing an evolution of the Nike Vaporfly 4%.
They are called 4% because they are supposed to make you run 4% faster. And what sounded like a marketing stunt at first, turned out to be true. It was the beginning of a revolution in running.
And a huge controversy. Suddenly everyone was talking about the so-called “super shoes”. About “technological doping”, or “cheating”.
Every mildly ambitious runner tried to get their hands on a pair, new drops were sold out immediately. And even professional athletes who were sponsored by other brands started secretly wearing Nikes and painted over the swoosh. Records started to fall.
Of the 10 fastest marathon runners in history, 9 did it in the last few years wearing - you guessed it - super shoes. The advantage of the shoes became so apparent, that World Athletics even banned some of the models. But not all of them.
And fast forward to today, it is no longer just the marathon. At the Paris Olympics, many of the Track World records are under scrutiny because of super shoes. Usain Bolt is not happy about that.
He called the new shoes “weird… and laughable” that they are even allowed in competition. So what’s so special about these shoes? And are they an unfair advantage?
Welcome to Athletic Interest. The first known running shoes appeared in the 1860s, looking like dress shoes but with spikes for traction. In the 1920s, rubber soles started to revolutionize the market.
After WWII, Adidas and Puma, founded by the Dassler brothers, introduced key innovations like track shoes with changeable spikes. In the 60s, this guy entered the scene. Bill Bowerman, co-founder of Nike, created the Cortez, a shoe with improved cushioning.
This is the model that, for no particular reason, Forrest Gump decided to take for a little run. Bowerman later destroyed his wife’s waffle iron to create another innovation, the Nike Waffle Trainer. Since then, running shoes have continued to evolve, becoming lighter and more specialized.
But the real game changer came in 2016. And after equipping Forrest Gump and breaking waffle irons, it was again Nike pushing the boundaries. With the Breaking2 project.
The idea: to break the last once-in-a-generation barrier. After the 4 minute mile in 1954, the first sub-10-sprinter in 68, Nike wanted to break the 2-hour marathon. They organized a private race and chose the Formula 1 track in Monza for its low altitude, calm weather conditions, and short lap length.
A team of pro runners served as pacemakers to shield the key athletes from the wind. Although Kipchoge missed the 2-hour barrier by 25 seconds, Breaking2 delivered the groundwork. And in 2019 in Vienna, he became the first man to run a marathon in under 2 hours.
The one thing everyone was talking about after the race: the shoes. He was wearing the Nike Alphafly, which is similar to the Vaporfly but also has two Air cushions. Countless studies were made on the effect of the shoes.
The New York Times, for example, analyzed data from more than a million races that were logged with the running app Strava. The result: the shoes make most runners faster, sometimes even more than 4%! So how do the shoes actually work?
Over time, running shoes have standardized into three main parts: the upper, the midsole, and the outsole. The upper is the part that covers the top of your foot. It's designed to be light and secure, keeping the shoe snugly on your foot.
The outsole is the bottom part of the shoe that contacts the ground. It provides traction and durability. While outsoles used to be the main focus, nowadays, the spotlight is on midsoles.
The midsole is typically made of foam and provides cushioning for the runner's foot. The key to a great midsole is energy return: how much energy you get back when the midsole bounces back after being compressed. Most modern shoes return around 50-65% of energy back to the runner.
But the Nike Vaporflys? They return about 85%. So, what makes the Vaporflys so special?
This is where things get a little complicated but bear with us. Energy return depends on a combination of compliance and resilience. Compliance is how much something gives when you apply pressure.
Resilience is how much of that pressure is returned back to you. Imagine running on sand — it's very compliant but not resilient. It gives way under your feet but doesn't push you forward.
On the other hand, concrete is very resilient but not compliant — it pushes back but is hard to compress. Nike's Vaporflys strike the perfect balance between compliance and resilience, thanks to two key innovations. First, they use Pebax foam, branded as 'ZoomX foam’ because this just sounds cooler.
This foam is incredibly light, allowing for a much thicker midsole without adding weight, which is why most of the super shoes have this ridiculous look. And it gives back A LOT of energy compared to other foam as you can see in this experiment by Pebax. The second innovation is a carbon fiber plate.
This plate is super resilient, providing a snappy feel with each step. It basically works a bit like having a spring under your feet. Combined, the thick foam and the carbon fiber plate create an unmatched energy return, improving a runner’s efficiency by around 4%.
Now you might think 4% is not a lot, but in a marathon, 4% is a huge difference. At the Tokyo Olympics men’s marathon, it was the difference between winning gold and place 15! So while runners were busy getting their hands on a pair of Vaporflys, and other brands started to develop their own super shoes for the marathon - Nike was already busy developing shoes to break more world records.
And at the Olympics, there is one track event that shines brighter than all the others: the 100m. And the question: who is the fastest man in the world? So Nike came up with the Viperfly.
This futuristic-looking shoe has similar benefits as the marathon shoe. A carbon fiber plate and a relatively thick midsole with foam. But there is more.
You see, speed is basically a combination of two things: stride length and stride frequency. The shoes help improve both. Because the foam and plate help reduce contact time on the ground, helping with higher frequency.
And the thick midsoles also simply extend your legs by 2cm, so you have a longer stride length. Now we already looked at how much 4% makes a difference in the marathon. But what about the sprints?
Let’s look at one of the favorites in Paris. Noah Lyles has a personal best of 9. 81s.
We don’t know the exact advantage yet, but let’s assume it’s not even the full 4 but around 3%. 3% of 9. 81s is .
29s. Which would make him break Usain Bolt’s world record. In the 200m, it would make him the first man to break the 19s barrier.
Now it isn’t as easy as that. We can’t forget that some of the personal bests were already run with advanced footwear. And every athlete reacts differently to the new shoes.
But even if the difference is just 1%, which the latest research can already measure based on yearly results, it’s still a massive improvement. It gives you an idea of what is possible with new technology. Another problem is that Lyles is sponsored by Adidas and not Nike.
But they have their own model of super spikes now. No wonder that athletes care more about their shoes than ever. Fred Kerley, 2022 World champion in the 100m, even switched to wearing Nike spikes despite being sponsored by Asics.
Which brings us to the crucial dilemma of this whole story. Are super shoes an unfair advantage? The answer is certainly yes if athletes do not have access to the same kind of equipment.
Running used to be a sport where the limit was set by physiology, not revolutionary equipment. There have always been incremental gains thanks to equipment, but it was spread equally and small enough that it was not as decisive. Suddenly, running is turning a bit into Formula 1, and the footwear sponsor is the team developing the engine.
Some experts say this hurts the sport massively. Also because the debate is already in the heads of the athletes, and they start to think that without these shoes, they cannot run as well. On January 31st, 2020, World Athletics reacted - and announced a significant rule change that everyone had been waiting for.
They limited midsole thickness to a maximum of 40mm and allowed only one stiff plate in the midsole. This ruling made some prototypes illegal, including the sprinter-specific Viperfly. However, for Nike, it was mostly a win.
Their core super shoe products remained legal. The new rules also said that shoes used in competition need to be available for purchase through official retail channels - to ensure that everyone has access to the same kind of equipment. This does help level the playing field and luckily most brands have caught up with Nike and developed their own super shoes, making it less important what brand you are attached to.
But the problem is not entirely gone. The advances in running shoe technology are truly fascinating. But let's not forget, it's the athletes themselves who make these shifts possible.
They are the ones breaking records and creating the stories that captivate us, all while generating significant profits for the shoe companies.
