The spike plate argument is really about ankles

Debate over stiff-plated footwear keeps circling energy return when the mechanism that matters is what the plate does to joint torque.

Every conversation about modern spikes turns into a conversation about energy return, and it should not. Foam gives some energy back. Plates give some energy back. Neither gives back more than it took, and the percentages involved are small enough that they would not, on their own, explain why fields have compressed the way they have.

The interesting mechanism is duller and more specific. A stiff longitudinal plate changes the effective lever of the foot and reduces how much the joint at the base of the toes bends during contact. That joint is a net energy loser. It absorbs work when the toes flex and returns very little of it, and it is doing that on every single step. Take a chunk of that bending away and you have not created energy, you have stopped throwing some away, and you have done it at the joint least able to argue back.

The knock-on lands at the ankle. With the forefoot held straighter, the calf and Achilles work at a different length and the whole lower limb behaves as a longer, stiffer strut. For a lot of athletes that is a gift. For some it is a problem, and the problem shows up as Achilles and bone stress complaints in the tissue that is now doing more of the absorbing, which is precisely the pattern coaches have been describing since the current generation of footwear arrived.

So the honest framing is not that these shoes are free speed. It is that they redistribute load, and redistribution has winners and losers.

I would draw a practical line from that. If a plate is doing part of the ankle's job in racing, the ankle should still be trained to do it in preparation. Athletes who spend an entire season in stiff footwear, on hard surfaces, and then race in something stiffer again, have taken a joint out of service for months and asked it to be strong on the one day it matters. Some flat-shoe work is not nostalgia, it is maintenance.

The governing bodies have regulated stack heights and plate counts, which is a reasonable place to draw a line and a slightly beside-the-point one.

Nobody has yet regulated the thing that actually changed, which is how much of the foot the athlete is still allowed to use.