Before, during and after Eliud Kipchoge's amazing 1:59:40 marathon distance run there has been a great deal of discussion about the shoes he wore and how much they contributed to his amazing acheievement.
The prototype shoes that Kipchoge wore, the Nike Alpha Fly, were specifically built for him and are a amazing piece of technology containing the latest foams, 3 carbon fiber plates and 4 forefoot pods (air or foam filled). The midsole is comprised of four different levels: a top layer of foam, a second layer of composite material, a third plate layer (possibly carbon fiber), and a bottom layer of more foam (see the image below). The forefoot pods are designed specifically to maximally return compressed and stored elastic energy. Pretty cool!
To explain how the technology works it's worth looking at the Nike Vaporfly 4% and Next% shoes that have helped elite distance runners make dramatic improvements over the past 2 years. Both the men’s and women’s marathon world record has been broken by athletes wearing these shoes and the top five marathon times of all time were all run in Nike Vaporfly shoes. Clearly they are the shoe of choice for the worlds fastest marathon runners! (see the pic from the start of the Melbourne Marathon last week)
The Nike Vaporfly have a dramatically thicker and less dense midsole sole compared to other racing flats. The midsole ZoomX foam is very light and has amazing energy-return capability compared to conventional midsole materials. So whilst they may look bulky and heavy, they are as light as a typical minimal racing "flat" shoe. The Vaporfly weighs less than 200g which is a 1/3 lighter than a standard neutral shoe. Research has shown that for every 100g of added weight on the foot of the runner, the metabolic energy of running will increase by about 1%.
The other structural feature that makes the Vaporfly special is the carbon plate running through the midsole. Carbon plates in shoes are nothing new but the use of the curved plate appears to reduce the work it takes to generate propulsion from the big toe when running. This is similar to the rocker systems employed within many shoes. Essentially the shoes help the lever at the forefoot work as best as possible without compromising movement efficency in other parts of the foot.
The Alpha fly appears to be an evolution of these technologies, tailored over many iterations for one athlete and one specific goal. The process clearly worked and has led to an IAAF investigation into the legality of certain bespoke shoes, and claims that the sub-2 attempt was tainted. Regardless, its got people talking about running shoes and whether you love or hate Nike, the discussion can only help grow the running industry as a whole.
For recreational runners it's an exciting time as these advanced technologies flow into the running shoes that we use for day-day running. The prospect of lighter shoes, with high levels of energy storage can only be a good thing!
So yes I will be eagerly watching this space as other companies release their technolgies and shoes keep evolving.
Happy Running!
Thanks to Kevin Kirby, Simon Bartold (Bartoldclinical.com), Robbe Redinger (believeintherun.com), @BenJohnson763 for the knowledge, insights and images that have helped develop my knowledge on this subject!
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