Nike’s new Epic React running shoes fit like a slipper, but a sandwich of carefully crafted materials in the sole protect your feet and the tiny bones within from punishing pavement. The fresh kicks, which hit stores on February 22nd, embody a sock-like fit with a novel midsole meant to return energy on each stride. And unlike midsoles of the past these newly engineered foam layers supposedly don’t lose their bounce as the miles add up.
What’s new about these shoes?
Over the past several years, many running shoe companies have narrowed in on the midsole—that cushiony foam layer that’s squeezed in between a shoes’ insole and the traction-y bottom. A midsole is important for any type of shoe, but it’s especially so for a running sneaker. The foam compresses and rebounds with each stride to actually push you forward. That’s called energy return and it’s a metric that running shoe engineers have been working on for years.
A higher energy return means that the runner has to do a little bit less work each time they take a stride. Nike claims that the React returns 13 percent more energy than the shoes.
But that’s not Nike’s only brag for its new shoe. The Epic Reacts also employ a brand new midsole. According to the company, the shoes contain a newly designed synthetic rubber that can’t be found anywhere else. Unfortunately, it’s also proprietary to Nike, so details are sparse, but we might be able to hazard a guess.
Midsole foam is often made from EVA, which provides pretty decent energy return. However, after several hundred miles or so, the midsole starts to lose its elasticity and the energy return becomes much worse. Plus, a typical EVA midsole needs about 24 hours rest to bounce back from its last workout. When you pound the ground, the midsole constantly compresses and expands and needs time in between workouts to return to its natural state. So if you ran on Monday morning, you have to wait until Tuesday morning at the same time before the shoe is fully functional again. Workout in them on Monday night and the midsole hasn’t had time to fully expand back to its original form.
The new midsole in the Epic React shoes don’t need this 24 hour recovery period and they also don’t start to lose their effectiveness after the 250 or so hundred miles mark.