Rethinking The Plate

Carbon fiber plates in shoes have captured the minds, imaginations, and conversations of runners worldwide. The Nike Vapor Fly was shown to improve running economy by an average of 4% by my guest in episode 40, Roger Kram. Now, a former student of is has done the unthinkable…take a new pair of ~$250 Vapor Fly shoes and cut the plate. Above, you’ll see a figure from the paper (preprint) showing the location of several cut lines used to segment the plate, taking away its capacity to act as a lever through longitudinal stiffness (the hypothesized reason for its economy-improving benefits).

And….drum roll…nothing happened. Cutting through the plate should have made economy worse, if the plate’s longitudinal stiffness is the mechanism for how it works, as previously thought. But that’s not what happened. Whether the plate is cut or not, runners had the same running economy.

These shoes still provide the significant economy-reducing benefits compared with traditional running shoes. So what gives? The authors speculate that “the plate alone plays a limited role in the 4% energy savings, and instead those likely result from a combination and interaction of the foam, geometry, and plate.”

Clearly, this area of shoe technology is far from understood. The coming years will be an exciting time for shoe innovations. It’s fun to see that even gear can be made to ‘work’ without fully understanding how it does.