This Lightweight Foam is Revolutionizing Running Shoes

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We’ve seen the future of running shoes, and it looks a lot like Nike’s heavily hyped Vaporfly 4% — or, at least, the white foam part used in the much-hyped road racer. The shoe is packed with a ton of performance technology, like a carbon-fiber plate, but its new midsole made from a thermoplastic called Pebax, which yields cushioning that is not only lightweight and extremely soft but also exceptionally springy. Until now, those three characteristics have proven nearly impossible to achieve.

Reebok, too, has released a shoe, the FloatRide Run, this year using a foam made from Pebax. Typically used as a hard but flexible plastic component in running shoes, like the Wave plate Mizuno uses or The North Face’s cradles that hold your heel in place. Pebax has a lower density than some thermoplastic alternatives, making it lighter, flexible, more impact-resistant, and capable of returning a whole lot of energy. When blown into a foam, those properties remain, meaning you can compress the foam more and still have it bounce back with more force than other materials we’ve seen used in running shoes.

The result? You get a lively underfoot sensation that encourages you to run fast. In fact, every run we’ve done in the Reebok has unintentionally turned into a speedwork session.

How We Got Here

For decades, running shoes used EVA (ethylene-vinyl acetate) for the cushiony midsole that let runners pound out miles relatively free of pain. It was thicker in the heel because that’s where we landed first, thus more was better, softer. The material is still used today because it’s versatile, soft, flexible, and, importantly, cheap for manufacturers. The problem: it compacts fairly quickly and loses its cushioning power.

Then came the quest for “energy return.” In spring 2013, Adidas eschewed EVA for a midsole made from thermoplastic polyurethane (TPU). In its Energy Boost shoe, the company used a slab of a bouncy foam made from plastic pellets that were fused together using heat and pressure. The result was a shoe that not only absorbed shock incredibly well but returned that energy with every toe-off (like a spring). The TPU-based midsole also proved more durable and its cushioning powers remained unchanged even on extraordinarily hot and cold days (EVA, by contrast, gets harder in cold weather). Its one downside: TPU is heavy. But that was a trade-off most brands were willing to accept, as nearly every shoe maker has scrambled to release their own spin on the formula.

The Future

The success of the Nike Vaporfly 4% and Reebok FloatRide Run must leave every company scrambling again to find a way to get this new, lightweight miracle foam — or their own spin on it. In the short term, your options are limited to just three shoes.

We’ve been testing another Reebok model with a Pebax midsole called the FloatRide Racer. It is, obviously, a road racing flat, set to be available in 2018, and is lighter than most options on the market (our size 12 sample checked in at just 4.1 ounces). The Racer paper thin, with a very slim layer of foam separating your foot from the road, and a see-through upper has just enough material to keep sole attached to your foot. Typically, such a shoe will be hard — the only real goal of flats being to reduce weight and let you run fast — but that’s not what we found.

Racing the 5th Avenue Mile recently, we were astonished to find none of that teeth-rattling ride, even when bombing downhill to the finish at 5-minute pace. In fact, a cooldown jog post-race was also comfortable, giving us the confidence to try it in upcoming 5-K and 10-K races.

The only issues so far: cost and availability. Both the Nike Vaporfly 4% and the Reebok FloatRide Racer will set you back $250 — if you can find them. The Vaporfly is sold out everywhere and the Racer won’t go on sale for another 6 months. The Float Ride Run, however, is your best bet to experience this new foam. It costs “just” $150 and widely is available now.

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