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Jul 15, 2023

How Running

New, high-tech foams like those in Adidas’s Boost footwear are making it

New, high-tech foams like those in Adidas's Boost footwear are making it possible for cushioning and responsiveness to coexist—so you can run faster, stronger, longer.

Over a lifetime, the average person will take enough steps to travel the equivalent of the Earth's circumference more than five times. Yet how many of those steps will get even a passing thought? Though it's easy to take them for granted, your feet—the facilitators of all those steps—are incredible. They interact with more than 100 other muscles, tendons, ligaments, and bones in every single stride. They are the body's primary shock-absorption system and provide stability with their strong arches. They support heavy loads of one-and-a-half times your body-weight when you walk, and between five to seven times when you run.

So much pounding takes a toll—and not just on the feet. While the whole "running destroys your knees" thing has been more or less debunked, injuries are simply a fact of almost every runner's life. And every runner's primary pieces of equipment—their shoes—are the first line of defense against injury.

The mission of running-shoe makers, then, is clear: Diminish the effect of all that impact and keep runners moving, healthy and happily, for as long as possible. Fortunately for us runners, there has never been a more exciting time in running-shoe design, with new technology like that in the Adidas Boost line successfully reducing impact on feet and joints, while simultaneously helping propel us ever faster.

Shoemakers’ approaches to impact-reduction and injury prevention have evolved over time. In the 1970s, sponge-rubber midsoles emerged, establishing the idea of cushioning in running shoes. EVA (ethylene vinyl acetate) foam became the industry standard and remained so for decades. From the 1980s to early 2000s, firm, heavy shoes with with plastic posts, shanks, trusses, and multi-density foams to control the wearer's stride were the longtime standard. Next came the "barefoot" craze. Finally, in the most recent decade, comfort became king; new materials were engineered to create more flexible uppers and super-cushioned midsoles.

All of these had pros and cons, but two key ideas seemed to persist. First, comfort is highly subjective: One perfect shoe/foam combo doesn't exist for all runners. Second, running shoes could either be soft or fast, but couldn't be both. Both led to the era of innovation where we currently find ourselves. Designers want to give every runner the opportunity to feel comfortable. They also want to help reduce injuries while driving runners to new heights of performance. The result is an arms race to deliver the sweet spot between a shoe that feels light and springy, but can also withstand the pounding of hundreds of miles. And the not-so-secret weapon is new, high-tech foam.

Adidas has been on the forefront of the cushioning revolution since 2013, when the Adidas Innovation team and German chemists BASF introduced their now ubiquitous Boost technology. Boost midsoles are made from thousands of Thermoplastic Polyurethane particles, which are expanded to form closed cells around tiny pockets of air. The resulting product, known as expanded Thermoplastic Polyurethane (eTPU), delivers a greater sensation of what's known as "energy return"—the feeling that your shoes are actually generating propulsive forward momentum out of the forces created with each footfall.

While it's scientifically impossible for a shoe to literally return energy to your body, what eTPU does far better than traditional EVA is dissipate the force needed to compress the foam. Or, more simply, eTPU foams lose less energy. And Boost remains the gold standard in this regard. The difference is that Boost doesn't stop at absorbing impact forces into a thick pillow of foam. Boost soles firm up with each footstrike for a more powerful push-off.

The next frontier in footwear

Boost just may have achieved the seemingly impossible: combining cushioning with responsiveness. On top of that, Adidas has literally journeyed to the next frontier of design and testing by partnering with the International Space Station, where Boost pellets will be tested in zero gravity to deliver the next generation of cushioning.

Down here on earth, the all-new Ultraboost 20, whose design was inspired by the new partnership, already features a new Primeknit upper with Tailored Fiber Placement (TFP) technology for flexibility and control that's unique to each runner, a 3D Heel Frame that firmly cradles the heel in place, Continental rubber for maximum traction, and Torsion Spring construction for enhanced landing and transition support. Combine that with optimized Boost in the midsole (the most responsive yet) and you get a cloud-like feel that's snappy, strong enough to perform over the long haul, and flexible enough to deliver a smooth ride at any pace.

Or, put another way, a shoe that helps you finally appreciate your amazing feet in the best way possible: by lightening their load.

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