Speedy Shoe

Last November, Shalane Flanagan became the first American in 40 years to win the women’s division of the New York City Marathon. Her victory wasn’t the only thing that sparked a lot of buzz. During the 42.2 kilometer (26.2 mile) race, Flanagan wore a new sneaker, the Zoom Vaporfly 4%. Nike created the shoe to try to help elite runners complete a marathon in less than 2 hours—a goal that remains just out of reach.

Last November, Shalane Flanagan won the women’s division of the New York City Marathon. She was the first American to do that in 40 years. Her win wasn’t the only thing that sparked a lot of buzz. Flanagan wore a new sneaker during the 42.2 kilometer (26.2 mile) race. It’s called the Zoom Vaporfly 4%. Nike made the shoe to try to help top runners finish a marathon in less than 2 hours. That goal remains just out of reach.

Nike engineers designed every aspect of the Vaporfly to help long-distance runners conserve as much energy as possible. Its ultralight weight means a runner doesn’t have to use as much energy when lifting his or her feet. A soft foam in the sole bounces energy back to the wearer with every step. And a curved plate made of carbon fiber inside the foam prevents a runner’s foot from bending too much with each stride, which would waste energy. Carbon fiber is a strong, light material made of the element carbon (C).

Nike engineers designed every feature of the Vaporfly to help long-distance runners save as much energy as possible. The shoe is extremely light, so runners don’t have to use as much energy to lift their feet. A soft foam in the sole bounces energy back to the runner with every step. And a curved plate made of carbon fiber is inside the foam. Carbon fiber is a strong, light material made of the element carbon (C). The plate stops a runner’s foot from bending too much with each step, which would waste energy.

Once the design was complete, Nike turned to scientists at the Locomotion Lab at the University of Colorado Boulder to test the shoe’s performance. Using a lab device, the researchers measured the compression of the sole. They found that it compacted about twice as much as other top-performing shoes when the device pushed down on it. And when the sole rebounded, it returned about 87 percent of the energy put into squishing it back to the device, beating its competitors.

When the design was complete, it was time to test the shoe’s performance. Nike turned to scientists at the Locomotion Lab at the University of Colorado Boulder. The scientists used a lab device to measure the sole’s compression. When the device pushed down on it, the sole compressed about twice as much as other top shoes. When the sole rebounded, it gave the device back about 87 percent of the energy put into squishing it. That beat the other shoes.

To see if that bounce-back helped runners save energy when the shoes were on their feet, the scientists had 18 runners test the shoes on a treadmill. Researchers measured the oxygen the runners breathed in and the carbon dioxide they breathed out to calculate how much energy their bodies used as they ran.

The result: “We saw a huge energy savings of 4 percent with Nike’s shoe,” says Wouter Hoogkamer, a sports biomechanist at the Locomotion Lab. He studies the physics of how bodies move. Does the shoe really shave time off races? We may never know for sure, but top runners are taking the design to the proving ground that matters most: the pavement.

The scientists wanted to see if that bounce-back helped save energy when people wore the shoes. So they had 18 runners test the shoes on a treadmill. Scientists figured out how much energy the runners’ bodies used as they ran. To do this, they measured the oxygen the runners breathed in and the carbon dioxide they breathed out.

The result? “We saw a huge energy savings of 4 percent with Nike’s shoe,” says Wouter Hoogkamer, a sports biomechanist at the Locomotion Lab. He studies the physics of how bodies move. Does the shoe really take time off races? We may never know for sure. But top runners are taking the shoe to the testing ground that matters most: the pavement.