There is a reason carbon fiber is used on high performance cars. Carbon fiber is stronger than steel and aluminum, and also lighter than both. Have you ever tried to bend one of these shoes?...good luck! If any plate in a shoe were to act like a spring, it’d be a shoe like the Saucony Speed or the Zoom Fly OG/SP due to the nylon plate. As nylon isn’t near as rigid as carbon fiber obviously and can bend.
The plate in the Vapor/Alphafly is there for 3 reasons by my estimation. To give the ZoomX structure, to make the shoe a “rocker” style shoe, and to make your foot rigid. The ZoomX foam is there for 2 reasons by my estimation also, and that is “padding/protection” from the foot strike and to get you up onto the “S curve“ of the plate. If anything is a spring...it’s the foam...and in all honesty it’s not a very good one. It’s better at keeping your feet and legs from getting beat-up more than anything. Which is pretty evident by how many people say how good their legs feel after a marathon in these shoes.
These shoe literally turns your foot into a lever, due to the plate not allowing it bend like a normal shoe. Try taping a piece of 2x4 to the bottom of your shoe. That is essentially what the plate is doing but with an “S curve“ in it to propel you forward. This is why some people struggle with them. Carbon plated shoes should not be used most of the time. Your ankles can atrophy a bit if used too much.
But anyone that says the carbon fiber plate is a spring doesn’t understand the rigidity of the material. A guy like Kofuzi always talks about “pop” in carbon plated shoes In his videos and it makes me cringe a bit because he doesn’t really understand the mechanics of it.
Spot on. The shoe effectively turns your foot and ankle system into a "spring". This is how I think of it and also experience (in 4%s)