Do Nike's new shoes give runners an unfair advantage?

Shoes cushioned the feet of all three medalists in men's marathon at the Rio Olympics last summer

The shoes came in the colours of a tropical drink, lime and orange and pink, as if the logo ought to be an umbrella instead of a Nike swoosh. You half expected the insoles to smell of rum and coconut.

If the colour scheme suggested frivolity, race results did not. The shoes cushioned the feet of all three medalists in the men’s marathon at the Rio Olympics last summer. Later, in the fall, they were worn by the winners of major marathons in Berlin, Chicago and New York. The latest shoe designs have produced fast times and impressive results in international