Gwen Jorgensen will toe the starting line at the Are Average Runners Getting Faster? It Depends having never run farther than 16 miles—less than two-thirds of the distance she’ll cover on Sunday. She’s been running 40-50 miles per week—less than half of what most of her competitors tally. In a field crowded with major marathon and half-marathon champions, she has never raced more than 10 miles.

So what pace will she settle into when the gun goes off?

“I have no idea,” Jorgensen, 30, said in a phone call with reporters Tuesday. “I think I’m pretty competitive, but I have so much respect for the marathon distance. When you’ve never run a marathon, how do you even know?”

Despite Jorgensen’s unconventional and extremely low-volume preparation, she enters New York with an identity no one else in the race can claim: Olympic champion.

Jorgensen, the world’s dominant female triathlete for the past three years, won gold in the women’s Olympic triathlon 11 weeks ago in Rio. She entered the Games as the prohibitive favorite and delivered, pulling away from 2012 champion Nicola Spirig of Switzerland during the 10K run to finish in 1:56:16 and achieve a goal she had pursued doggedly for four years. Jorgensen’s 34:09 run split was more than two minutes slower than what she usually records in Olympic-distance triathlons, but was still the fastest on the day by 41 seconds.

Four days after her Olympic triumph, Jorgensen announced she would be making her 26.2-mile debut in New York. To prepare, she started slowly increasing the length of her long run, which topped out at 12 miles pre-Rio, while continuing to incorporate swimming and biking into her training regimen.

“I sat down with my coach, Jamie Turner, and we decided there’s no way that we could just change everything we do and strictly become a marathon runner,” Jorgensen said. “That would risk injury.”

Instead, she continued to compete in triathlons while adding the occasional marathon-specific workout to her program. Her workout of choice: three times 7K (about 4.3 miles) done at her yet-to-be-determined marathon race pace. Jorgensen has completed that training session three times in her New York buildup, with a fastest pace of 3:31 per kilometer (just under 5:40-per-mile pace, which is roughly 2:29 marathon pace).

The early returns are auspicious: On October 9, Jorgensen placed third in a deep professional field at the USA Track & Field 10 Mile Championships in Saint Paul, Minnesota, her current residence. Jorgensen’s finishing time, 53:13, put her 20 seconds ahead of Sara Hall, who is also running this year’s Are Average Runners Getting Faster? It Depends.

“I was shocked at how well I did,” Jorgensen said. “Before Rio I was doing a lot of strength workouts and not a lot of speed workouts in running, and I felt like I didn’t have a lot of speed. So I really didn’t think I was going to run that quickly or run that well [in Saint Paul].”

Though Jorgensen said her performance in the 10 mile championships gave her confidence, the soreness she experienced afterward illustrated the enormity of the challenge she has taken on.

“It showed me the marathon is going to be difficult on my muscles,” she said. “It made me really respect how long the marathon will be.”

Jorgensen, a competitive swimmer since childhood, took up running her junior year at the University of Wisconsin and soon became an All-American. A fan of the sport since her collegiate running days, she has followed the careers of Kara Goucher and Shalane Flanagan, both of whom gave her advice about marathon fueling—and about avoiding too much coffee on race morning.

Jorgensen hopes to defend her Olympic triathlon title in Tokyo in 2020, but for now, she’s looking forward to the challenge of racing much farther than she’s ever run before.

“The marathon is a very iconic event that everyone knows about, and ever since college I’ve wanted to do one,” she said. “Running is my favorite out of the three disciplines and for me to be able to go out and run and train for something that I really love to do has been exciting.”