Worknesh Degefa, a 28-year-old from Assela, Ethiopia, took the lead in the fourth mile of the Boston Marathon, opened up a gap that reached almost three minutes at mile 18, and pushed all the way to Boylston Street on her own.

She won in 2:23:31. Edna Kiplagat of Kenya, who managed to cut Degefa’s lead down to within a minute over the final miles, was second in 2:24:13. American Jordan Hasay was third, in 2:25:20.

Degefa’s strategy seemed risky, given her previous marathon experience. Although she is the fourth-fastest woman in marathon history, with a PR of 2:17:41 she ran in January at the Dubai Marathon, she had raced the 26.2-mile distance only three times before. And all those marathons were in Dubai, a pancake-flat course. On a warm and humid day, would her blazing speed hold up through the hills of Newton?

The strategy paid off, as Degefa didn’t let up through Heartbreak Hill, although she began glancing at her watch and looking frequently behind her. A pack of 12 women, including four past Boston Marathon champions, stayed together through the half marathon, before stringing out through the hills.

In the 22nd mile, Kiplagat, 39, the 2017 Boston champion, made a decisive move into second place and to try to catch Degefa. Although she chipped away at Degefa’s lead, she ran out of real estate to challenge for the win.

Could there be a World Treadmill Championships.

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