Courtesy Hannah Zarzecki // Hearst Owned

On a rainy Saturday in June 2024, Hannah Zarzecki cried as she crossed the Grandma’s Marathon finish line. It was her eighth marathon , and despite following a training plan, she didn’t achieve her sub-4 goal— again . “I kept telling myself, ‘Why did I sign up for this? I still can’t PR. I’m freezing cold. My feet hurt,’” she says. “It was so miserable.”

She didn’t know that a chance encounter at that race was about to change that.

A high school cross-country runner, Zarzecki returned to the sport after graduating from Harvard University, where she played ice hockey. Wanting a goal to work toward, she entered the 2018 Chicago Marathon lottery and won a bib in her hometown race.

Leading up to the race, Zarzecki had not run more than about 15 miles and didn’t follow a training plan. She was in good shape from teaching spin classes several nights a week and wasn’t sure how else to prepare.…