Prototype variants of the Vaporfly used by Eliud Kipchoge to run the first sub-two hour marathon and by fellow Kenyan Brigid Kosgei to smash the women’s marathon world record were both reported to contain triple carbon plates inside thick, ultra-compressed foam, said by Nike to help improve running economy by up to four percent. Those have been banned and from April 30 any future version, of any shoe, must have been available to the general public for four months before being allowed in elite competition. That will put paid to the use by Nike and others of prototypes by their athletes in major races.