“I want to say, ‘Coach, this pace is so slow,’” she said, “and he says, ‘No, I know what I’m doing.’”

That has shown in her training logs and in her results. She won the New York City Half Marathon on March 19 with a course-record time of 1:07:21. (It’s a hard course; her best time in the distance is 1:04:22.) The next day, she moved to Boulder with her family.

She was quick to hop into training sessions with her teammates. On March 28, she joined Joe Klecker, one of her teammates, for a long run. For Klecker, a runner who focuses on the 5,000 and 10,000 meters, that meant doing 18 miles. Obiri did those 18 — plus another seven for good measure, all at a pace that hovered around 5:35 per mile, the equivalent of a marathon around 2:26.

“He went with Hellen and took the beating,” Ritzenhein said.

“Which is funny because it takes a lot to beat up Joe Klecker,” said Andrew Wheating, a two-time Olympian and the team’s operations and content manager.

Two days later, Obiri joined Klecker and the rest of the team for a workout. Ritzenhein figured that Hellen “has got to be tired.”

“You would think,” Wheating said.

Obiri was essentially doing a 50-minute fartlek run — a ladder of fast intervals with equal “rest,” which simply means running but not as quickly — alongside Alicia Monson. Ritzenhein was excited for Monson, the freshly minted American record-holder in the women’s 10,000. It has gotten more challenging to find women who can keep up with Monson.

Before the start of the run, Ritzenhein advised Obiri to take it easy.

“You just ran 25 miles,” he told her. “You have to go easy. Otherwise I’ll yell! I’m a big yeller!”