BOSTON — She may be 70. She may be known primarily as a pioneer for women’s distance running. The thing to remember about Kathrine Switzer, however, is that at the core of her story beats the heart of a competitive athlete.

Leading up to her celebratory run on the 50th anniversary of her landmark Boston Marathon – the 1967 race in which she became the first woman to officially complete the world’s most famous marathon – Switzer “harbored hopes” that she could beat the time she put up as a 20-year-old collegian.

As things turned out, she couldn’t. Switzer finished Monday’s race in 4 hours, 44 minutes and 31 seconds – about 25 minutes slower than she ran a half-century earlier, when an angry race official attempted to yank her bib (No. 261) from her for the audacity of being a female and running the race that had been an all-male affair.

“I had faith in my fitness,” said Switzer, who spoke of gut-busting 4-hour workouts in hilly New Zealand, where she lives four months a year with her husband, Roger Robinson. (She married Tom Miller, the boyfriend whose perfect block sent the race official flying in the famous series of photographs, in 1968, but they divorced within five years and he died of a heart attack in 1992.)

“The problem is, since early March, I have been flat-out working on my 261 Fearless Foundation and doing so much media. I guess I was slammed, so slammed that I haven’t been able to sleep more than three or four hours a night.”

There were mornings that, when she got out of bed, she found herself too dizzy to stand up.

“It was scary,” she said. The night before the marathon, “was another three and a half hours of sleep. Just ridiculous.”

Her husband and a race official told her she had nothing to prove, to dial it back, to walk through every water station. Heck, she could walk the whole way, and then run down Boylston Street to the finish.

“But it was coming together,” she said. “Still, I walked every water station. I stopped for eight interviews on the course. So maybe (without the interviews), I’m closer to 4:20. But every step of the way, I had enormous support.”

Monday’s race may prove more important than her debut, she said, “because what we have effectively launched with this race is 261 Fearless, our foundation, which is going to empower women around the world for the next 50 years.”

Switzer ran with 118 women and seven men who together raised $826,948 for her foundation, which aims to establish running clubs in societies and villages around the world.

“Change begins in your own town, and it begins with a direct touch,” she said, poking a questioner in the shoulder. “We’re creating a non-judgmental community of women and we’re using running as the vehicle to empower them.”

Seana Roubinek, 49, of Rockport was among the women running in support of Switzer’s charity, to the tune of $14,300. Roubinek put off surgery for ovarian cancer until the week after the marathon. She saw Switzer throw out a first pitch at Fenway Park on Sunday, chatted with Switzer at a prerace dinner that night and joined in a group photo Monday in Hopkinton for all the 261 Fearless runners.

“It was really hot,” Roubinek said. “I ended up walking a good portion of it, but I finished and I’m really happy.”

Darkness had descended by the time Roubinek and three other runners arrived in Boston. Because many of the roads had been reopened to traffic, they stuck to sidewalks until Boston Police closed off Commonwealth Avenue so they could run through the tunnel beneath Massachusetts Avenue and follow Hereford and Boylston streets to the finish line.

“They had the sirens going and everybody on Boylston poured out of restaurants and went nuts,” Roubinek said. “I’ve got to tell you, I cried from (the tunnel) on. The Boston Police insisted we stay on the street and take the same course that everybody else did. It was very cool.”

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