[bo1024]

If it were just "the shoes make you faster" there would be nothing to discuss. The debate centers around a qualitative difference: "The shoes have a 'spring' in them that make you faster."

It's similar to a mini version of prosthetics such as Pistorius's that were banned from Olympic competition, as they are basically big metal springs on the end of your legs. The Vaporfly was explicitly designed to use this spring principle, i.e. store mechanical energy in a carbon fiber plate and release it back on toe-off.

So some, like me, feel that shoes for competition should not be allowed to mechanically assist the runner. It's not about percentages, it's a simple binary criterion.

[GatorD42]

If you think the plate is such a qualitative difference you may have fallen for Nike's marketing. The vapor fly 4% is very lightweight with an excellent cushioning to weight ratio thanks partly to Nike's new zoomx foam (which possibly provides superior energy return too). Shoes with plates in them have been around for a while and nobody complained - Mizuno shoes have plates like this as does the Nike zoom fly (different shoe), neither shoe is very high on the list or higher than you would expect based on its weight alone.

Look at the top shoes on the list - the Nike streak is a super lightweight shoe without Nike's new foam and it is second fastest. This should tell you weight alone is probably the most important factor. Two other highly rated shoes are Adidas shoes with boost foam, a type of foam similar to Nike's zoomx with a better cushioning to weight ratio. So the newest generation of foam probably provides a small benefit apart from the she's weight alone.

Runners capable of running a three hour marathon probably know the single most important factor in a running shoe for speed is weight. If they still choose to run in Saucony Guide or Hokas there's probably a good reason. What percent of runners who switched to the Saucony Guide were injured and used the shoes to recover, and what percent of runners in heavier shoes with more cushioning and stability features made it to the Starting line vs runners in Nike streaks? It's possible the heavier shoes provide protection from injury or greater comfort - there's a reason runners don't race marathons in track spikes.

I don't think the plate provides much benefit apart from weight and cushioning, my guess is that it is there for the feel of the shoe and without it the new foam would feel too mushy.

[bo1024]

The point isn't whether I think it works in providing mechanical assistance. The point is whether it is intended to provide mechanical assistance, which as you mention from Nike's marketing, seems to be yes.

Try this: http://sportsscientists.com/2017/03/ban-nike-vaporfly-carbon...

By the way, it doesn't really bother me if 3-hour marathoners want to wear them, or even 2:30 marathoners, but if you're competing for prize money, I think this sort of thing should be banned. At least the sport needs a discussion of where to draw the line on such devices.

[GatorD42]

So if a faster shoe came along (Vapor Fly 5%) that didn’t use a plate, that would be okay? But if people preferred the Vapor Fly 4% over the faster shoe, they couldn’t use it because of the plate? . . .

The patent application Ross Tucker cites has close to zero applicability. Nike has been working on a different energy return “spring” shoe that probably would be illegal - the patent could be for those shoes. And people claim lots of things in patents, that doesn’t make the claims true. All shoes have some combination of firmness and cushioning, and shoes have used an embedded firm plate design before, and nobody complained.

What if a biomechanics lab proved the Vapor Fly 4% is not acting as a spring but makes runners more efficient through some other mechanism (firm underfoot feeling but lots of cushioning)?

[bo1024]

> So if a faster shoe came along (Vapor Fly 5%) that didn’t use a plate, that would be okay?

Right, according to my logic, it would be fine if there was a shoe that was faster empirically but not designed to cheat. (In other words, cheating is still cheating even if you're bad at it.)

Analogy: if a silver medalist is on EPO and the gold medalist isn't, the silver medalist is still cheating and the gold medalist still is not.

Your second paragraph does not match my understanding of the issue. I believe the Vaporfly is the shoe with the embedded carbon fiber plate, and I don't think other shoes (except maybe spikes) with this technology have ever been worn, at least in top level races.

[nradov]

Even regular foam soles have at least a little bit of springiness.

[themodelplumber]

I was just discussing this with a runner who uses Hokas. She said she thinks she gets a similar slingshot-like effect with them, maybe not as drastic but it's there.