When Adidas launched its first Boost shoe, the unique midsole cushioning sparked a revolution in shoe design. Suddenly every brand was rolling out its own proprietary midsole foam. Fast forward a few years, and the iconic Ultraboost has become the flagship running shoe for Adidas, and it’s still going strong: The company has released the Ultraboost 21, which goes on sale today. This latest version includes a stiffer forefoot and even more Boost foam to deliver the cushioned-yet-responsive ride that athletes have come to expect from the line.
In a press release, Senior Design Director of Footwear Moritz Höllmüller called the new iteration “our most holistic running shoe ever” and “everything you could possibly want in a running shoe.”
That’s some very high praise, but the Ultraboost 21 does come with major updates over the previous version. The main highlight is a redesigned midsole with a new feature called Linear Energy Push (or LEP): Essentially, it’s a layer of reinforced material in the sole of the shoe that reduces flexibility in the forefoot. That creates a stiffer platform for your feet at toe-off, and should contribute to a snappier, more responsive ride. Adidas claims it provides a 15 percent increase in forefoot stiffness over the last Ultraboost.
Of course, Boost cushioning foam is also a big attraction with this shoe, and now there’s slightly more of it: Adidas managed to squeeze in six percent more Boost by adding an “exaggerated heel curve.” Unlike traditional shoe cushioning materials, such as EVA, Boost is made from thermoplastic polyurethane pellets bonded together using steam. The result is a cushioning material that’s highly responsive and durable, and Adidas has continued to tweak the formula over the years. With the Ultraboost 20, for example, the company claimed it had increased the amount of midsole cushioning by 20 percent. Chemistry aside, the Ultraboost has won a devoted following for its propulsive ride.
Continental rubber provides grip and durability in key areas of the outsole, and on top, the Ultraboost 21 features a Primeknit upper that’s partially made from recycled ocean plastic. The shoe is available in eight mostly monochrome colorways—except for two that include bright fluorescent yellow accents, which seems to be an increasingly common running shoe color palette these days. Adidas plans to launch additional limited-edition versions in the coming months, so stay tuned for those as well.
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