The physics of springy shoes

It's like landing on a trampoline vs landing on sand. Ordinarily when you land your foot and ankle absorb the shock (this requires energy), the shoe is designed to reduce the shock through storing some of that energy in the spring.

They aren't "getting more out than they put in", that is physically impossible. When you run, much of the energy is lost / absorbed by the ground, joints, etc. With this new technology, the intent is to capture some of that "lost energy" in the shoe and utilize in future strides.

Yes, that was bad phrasing on my part - of course you can't get more energy out than has been put in (combination of stored spring plus stored human energy, plus wind / gravity too of course if you are going downhill with a tailwind!).

But what energy losses would the new shoe be sucking up? Where are runners losing energy to at the moment that sprung shoes overcome? Presumably there are very small losses which accumulate over a run (I'd imagine mainly heat into the shoe through friction / vibration?) which would be overcome by a well designed spring in the shoe plate?

rnr_ wrote:

They aren't "getting more out than they put in", that is physically impossible. When you run, much of the energy is lost / absorbed by the ground, joints, etc. With this new technology, the intent is to capture some of that "lost energy" in the shoe and utilize in future strides.

I'm curious to know if these shoes actually are a success, how will this impact local road races? Let's say a sub 20 guy in regular shoes just got beat by a sub 21 guy in spring shoes running a 19:3x? I feel like it's people cheating themselves if these shoes go mass marketing(which Nike will likely do right?) Perhaps I'm a little confused about it still.

When your foot hits the ground normally a good amount of your kinetic energy is transferred to the ground as heat and sound vibrations... with springy shoes some of the kinetic energy is stored as potential energy in the springs when you hit the ground and then is converted back into kinetic energy at the end of the stride

+1

This is cheating yourself if you think you have a new PR due to shoes that are literally conserving energy and pushing you forward. There was an article on wired yesterday where the guy said the shoes pushed him forward when he tried them on a run. This is cheating and I'm pretty surprised and disappointed the Nike athletes that have used them aren't embarrassed. I really liked Flanagan before but isn't she the one saying that dopers steal peoples dreams? I'm just a local runner but I feel like this is the same thing.

All marketing. The Adidas Boost material is superior.

Brev wrote:

When your foot hits the ground normally a good amount of your kinetic energy is transferred to the ground as heat and sound vibrations... with springy shoes some of the kinetic energy is stored as potential energy in the springs when you hit the ground and then is converted back into kinetic energy at the end of the stride

With springs in a shoe, the time that the shoe contacts the ground will increase leading to lower peak forces and more efficient energy transfer. It is like clap skates for speed skating. No one is regular skates now.

How would this plate be any different than the plastic wave plate in Mizuno shoes? Or in innovative foams designed to "return energy into the stride" or whatever marketing speak comes with it?

It looks like a shoe, it smells like a shoe, it fits like a shoe. It's a shoe.