MobileReply wrote:
They used a bending machine on the plate and then tried to calculate what it would return on the foot. I'm not spending $45 on the paper, so can't see their justification. The videos of the shoe flying through the air after being bent and released make me skeptical.
Even if it is right, how do we know they don't give better springs to their chosen ones? It would be a neat trick if we get 4% while Kipchoge has 10%. He can decline with age and go easy on other sources of assistance and we would never know. Just give him a slightly better spring every year.
It's ok though. Nobody paying attention believes anymore anyway. At least this time they are telling us it is fake.
They used a motorized force-measuring treadmill and motion capture software to determine the positions of the joints relative to the treadmill.
Here are some relevant quotes about the plate vs midsole:
"We estimate that if mechanical energy is stored in and returned from the NP’s carbon-fiber plate at the MTP joint, this would be at a rate of about 0.007 W/kg at most, providing ~ 35% of the posi- tive work rate at the MTP joint, but to put it in perspective, only ~ 0.3% of the positive work rate at the ankle (Table 3). This strongly suggests that, rather than being a spring, the carbon-fiber plate acts in parallel with the intrinsic foot mus- cles to stiffen the MTP joint."
"The NP midsole returned more than twice as much energy from compression as the other shoes, but the magnitude was only 0.17–0.18 W/kg more. Noteworthy, the NP midsole returned 0.318 W/kg from com- pression and just 0.007 W/kg from bending the carbon-fiber plate and midsole, almost 50 times more."
So basically it sounds like they look at the ankle and MTP joint (toes) and measure the amount of force delivered to/from those joints by your body and shoes to propel you, and they found that the effects were determined by the behavior of the foam, rather than the plate, as far as they can tell.