The call of nature cannot be put on hold. Esther Erb, though, decided it could be hurried — which prevented her from losing ground on her way to the women's championship at Sunday's Twin Cities Marathon.

Erb had to stop to use a porta-potty just after mile 20, when she was in third place. During her 30-second break, she was passed by another runner but quickly regained her position and started making up ground on leaders Heather Lieberg and Brianne Nelson. With about a mile to go, Erb seized the lead and held on to win in 2 hours, 34 minutes, 1 second.

Lieberg finished second in 2:34:09, and Nelson was third in 2:34:24. They led through most of the race until Erb ran the second-fastest time of her career to earn her first U.S. marathon championship.

"I was trailing [Lieberg and Nelson] for a long time," said Erb, 28, a native of Roanoke, Va. "I could see them up there, and I was just kind of trying to chip away. After I stopped in the portajohn, I made that 30 seconds up pretty quickly.

"In the last mile, I was kind of running scared. I was hoping they weren't right on my tail, because I know both of them are really fast. I didn't want to look back."

Erb was so excited for Sunday's race that she woke up at 11 p.m. Saturday, only two hours after she went to bed. After three restless hours — and a 2 a.m. snack — she was able to drift off for another 2½ hours before her alarm went off.

With a temperature of 37 degrees at the start of the race, Erb said her body had to work harder than usual to run the pace she wanted to keep. She didn't panic; after finishing third at the Twin Cities Marathon last year, she knew the course well enough to have confidence in her ability to move up in the later stages. After her bathroom break, she said, she was making up five to 10 seconds per mile.

By that time, Lieberg and Nelson had begun to struggle. "It was back and forth between us until mile 24 or 25," Lieberg said. "Then Esther came. She was 20 yards behind us. But my legs were pretty shot, and she passed us."

Erb is an assistant cross country coach at Rider University in New Jersey and won a Division III championship in the 10,000 meters at Case Western Reserve University. She also sang the national anthem at the 2012 U.S. Olympic marathon trials before running the race and finishing 27th.

Rushing through her pit stop Sunday — and staying just as fast, all the way to the finish line — gives her the chance to honor her country in another way. In addition to $26,500 in prize money, Erb and men's champion Tyler Pennel earned spots on the U.S. team that will compete at the 2015 world championships in Beijing.

"For me, the most important thing was making the U.S. team [for the world championships]," she said. "That's pretty much all that was on my mind the last mile or so."