adidas ADIZERO PRIME X 2 STRUNG, the illegal speed

  • The new ADIZERO PRIME X 2 STRUNG from adidas feature an innovative configuration with a 50 mm stack, but they do not comply with World Athletics rules, which limit the height to 40 mm. Therefore, they cannot be used in competition.
  • However, these shoes offer new possibilities for runners seeking to push their limits and for experimentation in running footwear.
  • They have innovative features, including a STRUNG UPPER, a Lightstrike Pro midsole with three layers of foam, and carbon plates to improve responsiveness, priced at 300 euros. They will be available starting September 15.


A new model has been added to the very fast ADIZERO family-that is, adidas’ highest-performance, fastest shoes: the new ADIZERO PRIME X 2 STRUNG.

There is one problem, however: by World Athletics regulations, these shoes cannot compete. In fact, the stack (i.e., ground clearance) limit imposed is 40 mm. In contrast, the ADIZERO PRIME X 2 STRUNGs have a 50 mm stack. Is that all? Mmm, not really: there is also carbon. Okay, carbon is allowed, right? Yes, but not in double-plate configuration.

Illegal stuff

At this point you might ask yourself the point of producing and selling a pair of shoes that you can’t use in races. There are several answers, but the first ones that come to mind are at least two:
1. Not everyone runs to compete, and there are also personal bests that are set on their own, without an audience, off an official event. They are called “overcoming one’s limits.”
2. Because experimentation points to new paths and new developments.

The first point needs no explanation and resolves itself into an inner dialogue between the person who wants to surpass himself and the tools he uses, regardless of whether they are the same ones he will use in the competition. The second is explained by Coralie Ho-Von, Global Product Manager Running Footwear at adidas:
Without the constraints of the usual rules, we had the space to unleash the full creative capabilities of our product design team. We could create a shoe that exceeds the limits of what is possible with running shoes. The data collected from the athletes allowed us to develop a shoe with more stability and elasticity in the forefoot and heel and an improved fit.

Here is the answer to (legitimate) doubts. It is called experimentation, and it serves to shed light on a vision of the future. That maybe it will not involve shoes with 50 mm stacks but midsoles with improved flexibility and next-generation carbon plates.

All innovations are accompanied by disbelief and rejection, except then-if they work-become commonplace and affordable.

Innovation in the details

It is not just about a resounding stack and two carbon fiber plates. The innovation of the ADIZERO PRIME X 2 STRUNG can be found elsewhere.


It is called STRUNG UPPER and is an upper made with careful layering in the midfoot and heel areas that need it most, and targeted flexibility in key forefoot areas. The knitted tongue is also designed to further enhance the blocking feel.

Lightstrike Pro X 3

Three are the layers of Lightstrike Pro, and then a Continental™ sole. No other adidas shoe has so many that they create a stack, as said, of as much as 50 mm. The new midsole is sandwiched between two full layers of foam and helps reduce weight and give more elasticity to the forefoot and midfoot.

Carbon squared

The core of Lightstrike Pro’s three layers is sandwiched between two carbon infused plates designed to create an even more responsive platform to accelerate your ride.


We are talking about extreme shoes, comparable to circuit-prepared super sports car models. That is why the price stands at €300. Available worldwide from September 15 via the adidas app, online, in stores and at selected retailers.


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