BISMARCK, N.D. — Dagny Knutson approached her 11th workout of the week with an intensity that burned like chlorine. Her coach, Kathy Aspaas, said Knutson’s pacing and purpose during the high-mileage practice harked back to when she was the most promising teenage swimmer in the country.

Aspaas had been skeptical when Knutson, 21, decided to make a comeback after retiring last January. But at the Bismarck State College Aquatic and Wellness Center three weeks ago, Knutson was outpacing expectations, her prospects of rejoining the national team improving with every stroke.

Two days later, shortly before Knutson was to begin her weekly training cycle anew, she sent Aspaas a text message.

“Don’t come to the pool,” she wrote. “I won’t be there anymore.”

Knutson stopped swimming a year ago to seek treatment for an eating disorder that she feared might kill her. She dropped out this month because her family’s savings were being siphoned by her medical bills and her college tuition. After losing her USA Swimming stipend, Knutson said, she did not have the money to finance her comeback.