Nike ZoomX Vaporfly: What are the shoes Eliud Kipchoge wore in Ineos 1.59 marathon and why are they controversial?

The Kenyan wore a bespoke version of the Nike Vaporfly trainers – called AlphaFLY – a major innovation in the sport which has seen performances sharply improve

Nike ZoomX Vaporfly: What are the shoes Eliud Kipchoge wore in Ineos 1.59 marathon and why are they controversial?
The Kenyan wore a bespoke version of the Nike Vaporfly trainers – called AlphaFLY – a major innovation in the sport which has seen performances sharply improve