The running world knows Shalane Flanagan for her heroic efforts in the Boston Marathon and for the bronze medal she won in the 10,000-meter run at the 2008 Summer Olympics in Beijing. But few know that as a teenager she ran in the 1998 Pikes Peak Ascent, the tough 13.32-mile trail run to the mountain's 14,115-foot summit.

Video interview with Shalane

And here is the kicker, Flanagan says the Pikes Peak Ascent was the experience that convinced her to pursue distance running.

"I don't think, at the time, I'd ever run anything over six miles," Flanagan said. "So it was quite the arduous journey. I had no idea what I was getting myself into, but I was like addicted. I thought it was the coolest race I'd ever run, and it was the most challenging thing I'd ever done. It really inspired me and kind of got me into distance running."

Flanagan, who lives in Portland, Ore., will compete in the 2014 Bolder Boulder on Monday as part of of the USA's Team Red, which also includes Deena Kastor (Mammoth Lakes, Calif.) and Sara Hall of Flagstaff, Ariz.

In her first and only trip up Pikes Peak, Flanagan placed eight overall in the women's race and won her age group with a time of 3 hours, 14 minutes, 37 seconds.

Though she has competed in some of the world's biggest and most competitive races, she vividly remembers Pikes Peak and the challenges that Barr Trail threw at her.

"They warned me, but I had no idea what elevation I was. I just knew that I was going to climb for a long time," Flanagan said. "I remember thinking, 'They call this a race?' I remember having to walk a lot. It's just a tough test. It tests everything. It tests your mind. It tests your body. But it's like one of the prettiest things I've ever done."

Flanagan finished seventh in the 2014 Boston Marathon, recording a personal-best time of 2:22:02. She said her decision to run at Bolder Boulder was "last minute," but her fitness coming off of the Boston Marathon is solid.

"My biggest challenge is racing at altitude," she said. "Its going to be tough, and I'll have to really calculate my energies really well, not having trained at altitude recently."

Flanagan was born in Boulder to parents who were runners. Her mother, Cheryl Treworgy, once held the women's world record in the marathon (set as Cheryl Bridges in 1971.) Flanagan said she can recall watching the Bolder Boulder as a child.

"I was that little kid sitting in the stadium watching all the runners come pouring in," she said. "And I remember thinking I want to do this race someday. My parents would run it. It's just a big celebration, super fun."

Flanagan trained in Colorado Springs during her run-up to Beijing, and again in 2013 prior to the Boston Marathon.

"I'm just a huge fan of the surface along the river (Monument Creek)," she said. "You can get some really good runs in, and it's a really good running community."