Rebecca Rusch is called the "Queen of Pain" for a reason. She's a three-time world champion in the 24-Hour Mountain Bike race, the 2011 National XC single-speed champion, and she's won the Leadville 100 mountain bike race four times.

But a couple years ago, Rusch decided to take on an entirely new kind of pain. It would involve an epic ride along the Ho Chi Minh trail to find the crash site where her father, a U.S. Air Force pilot, was shot down when she was just three years old. Her emotional journey is the subject of a new documentary called Blood Road. Rusch met up with XX Factor host Florence Williams at the Telluride Mountainfilm festival to explain why this was the hardest ride of her life.