The Journal writes, "The shoe model worn by Kipchoge has one carbon fiber plate and a sole thickness of 39.5 millimeters for a European unisex size 42—about a U.S. men’s size 8.5—according to Nike. That meets the rules of running governing body World Athletics, which limit sole thickness to no more than 40 millimeters and allow the inclusion of rigid material like carbon fiber as long as it is on one continuous plane." (link at bottom)
Yet the BBC says, "The prototype shoes worn by Eliud Kipchoge when the Kenyan became the first athlete to run a marathon in under two hours in October do not meet these restrictions.
But Nike said the retail version of the Zoom Alphafly Next%, set to go on sale this summer, will do.
"We are pleased the Nike Zoom Vaporfly series and Nike Zoom Alphafly Next% remain legal," said Nike in a statement."
So which is it? Did the Journal mistake NIke talking about the new commercial version of the Alphafly with the version Kipchoge actually wore? Or is the BBC wrong?'
But Nike in the BBC said the alphafly "will remain legal". Were they using legalese (there were no regulations when the race was run) to confuse the Journal to think that the actual shoe worn by Kipchoge was under 40 mm?
Many reports had said the Nike Alphafly worn by Kipchoge had a stack height of 50mm. This article below says 45.
But could it really have a 39.5 stack height as the Journal reports?
Personally, it seems unlikely everyone reporting the previous stack height was wrong. So I'd bet Nike is saying the released shoe will be under 40 and legal and the Journal assumed they were talking about the old shoe.
Or are there different ways to measure stack height and Nike will claim it is legal while others will say it's not?
WSJ and BCC articles below