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SOLE MATE

THE SCIENCE BEHIND A STATE-OF-THE-ART RUNNING SHOE

IN JANUARY, Nike unveiled the Epic React Flyknit, a running shoe featuring a sole made of a single block of foam that promises to combine performance and durability. Lightweight and springy underfoot, the shoe ($150, available Feb. 22 on nike.com) is also sturdy enough for miles of wear and tear.

1 PINK HEEL CLIP

The hot pink, horseshoe-shaped piece—standard on both the men's and the women's models—is a heel clip that is meant to aid in shock absorption and to provide extra stability for heel strikers.

2 FLYKNIT UPPER

The seamless, streamlined upper is a tighter version of Nike's Flyknit material. Constructed with a low-cut design, it provides breathability and stretchiness where it's needed most, in the tongue and toe-box areas. "We want it to feel like the upper just disappears," says Holts. "No distractions on the top of the foot, which helps amplify the cushioning experience that much more."

3 PROPRIETARY FOAM SOLE

Made of synthetic rubber (not unlike what is typically used for car tires), this white layer, dubbed Nike React, is the product of more than 400 test combinations in the company's chemical engineering lab and 17,000 miles of runner testing. It's the "lightest, softest, smoothest and most responsive foam that we've created to date," says vice president of Nike running footwear Brett Holts.

4 SOLE PATTERN

Using data collected from athletes' strides—how they move and with how much speed and force—Nike developed an algorithm to come up with the sole's pattern. The areas where the foam is cut deeper provide more cushioning while the shallower areas provide more firmness.