Among the famous names running the Bolder Boulder is Colorado native Ryan Sutter, the first winner of the reality TV series "The Bachelorette."
In the mountains near Vail, Sutter said he has been fighting an "uphill" battle.
"It would be nice to find some flat ground every now and then," said Sutter, laughing after finishing a two-hour training ride.
It's been seven years since the Vail firefighter's appearance on "The Bachelorette," when he won Trista Rehn's heart.
"It was only six weeks of my life, but it was the defining six weeks of my life," he said.
Now happily married to Trista and with two beautiful children, he was looking for a new way to define himself, he said, and he found "First Descents," a Boulder nonprofit that provides free outdoor adventure therapy for young adults with cancer.
"They have to combat nature because nature doesn't care if you have cancer or not. That river is the same for people with cancer or without," he said. "In turn, it sort of helps you put your cancer in perspective or your life in perspective."
Inspired by the cause, Sutter's new mission is to lead Team First Descents, raising funds and awareness at 10 athletic events across the country in 2010.
"The 10.10.10 challenge is we're hoping to inspire 10,000 people to donate $10 each. That's $100,000 that will have a ton of impact through First Descents," said Sutter.
His events start with the Bolder Boulder, and includes the Leadville 100, New York City Marathon and Lake Placid Ironman.
"There is no way I could do any of this without Trista's help. She basically takes the kids while I go on these long bike rides and things. It's a team effort," he said.
Still, juggling his family, firefighting job and grueling daily training has been a challenge, but he said that was the point.
"If you do get cancer, you're still going to have a family. You're still going to have a job. And you have to confront this ruthless disease," said Sutter.
In his own way, he is putting himself in their shoes, he said.
"It's supposed to be about embracing life and being thankful for the things you have and trying to give back and be helpful," he said.
To Donate to First Descents or join their team, click here