Is This the Craziest Sneaker You Have Ever Seen?

As soon as Hellen Obiri, the Kenyan distance runner and two-time Olympic silver medalist, takes her place on the starting line of the Olympic marathon in Paris next month, she will make history — though not for the reason you may assume.

For her shoes.

See, Ms. Obiri will be wearing the Cloudboom Strike LS, a new sneaker from On, the upstart Swiss brand started in 2010. But it doesn’t look like any sneaker anyone has ever seen.

“The first time I saw the shoes, I said, ‘No,’” Ms. Obiri said. “‘I can’t run with these.’” The shoes had no laces. They had no heel cap — a hard plate at the back kept the foot in place. They were made of a weird, stretchy, plastic-y material.

“In the changing room, even my colleagues were saying, ‘It’s a joke,’” Ms. Obiri said. “They were saying, “‘You can’t use these shoes for a marathon.’”

But then she tried them in practice. Then she agreed to wear them in the Boston Marathon in April. Then she won. And then, said Nils Altrogge, the director of innovation, technology and research for On, “She wouldn’t give them back.”