International track and field's governing body is imposing new restrictions on which shoes can be worn in elite competition, following years of controversy over whether Nike's Vaporfly line of shoes gives athletes an unfair advantage.
Elite marathon runners have seen major success wearing Vaporfly models. Kenyan marathoner Eliud Kipchoge, for example, was wearing a high-tech Nike prototype when he clocked a sub-two-hour marathon in Vienna last year.