Roughly a week after an international sports governing body issued a landmark ban against a type of Nike running shoe, Nike bounced back Thursday with a new model that it says meets all competition guidelines.
Officially called the Air Zoom Alphafly Next%, it's Nike's latest incarnation of the Air Zoom Vaporfly - models of which the World Athletics organization deemed unacceptable for giving runners what it said was an unnatural and unfair advantage...
And leading critics to describe the shoe as a type of "technological doping."
The new rules for running shoes, as laid out by World Athletics, state they must have soles no thicker than 40mm and not contain more than one rigid, embedded carbon fiber plate.
Nike's just-unveiled Alphafly has a sole thickness of 39.5mm and one carbon plate.
While most versions of the earlier Vaporfly fall under the new guidelines, one notable model does not - those worn by Kenyan runner Eliud Kipchoge in October when he became the first person to run a marathon in under two hours.
The race was unofficial for technical reasons, but his running shoes - which reportedly had extra-thick soles and three carbon plates - were nevertheless subsequently banned.
The Vaporfly controversy has since ignited a wider debate about where to draw the line between advances in sports technology and equipment that could give competitors an unfair advantage - be it with running shoes, soccer cleats or tennis rackets.
A Wall Street Journal report said limited numbers of the new Alphafly sneakers will be made available to the public online this month.
Consumer accessibility is one of the requirements, as dictated by World Athletics, for the shoe to be eligible for use at this summer's Tokyo Olympics.