But nabbing a spot in the Guinness World Records was never Sheehy's goal. Enlisting an army of supporters who cared about beating cancer was.

"I had never planned to run for charity or run for a record," says Sheehy, who used his vacation time for these pursuits. "But how do you get strangers to donate to you? You're not going to raise money by being an introvert. You've got to get out there and talk to people. You want to make it as inclusive as possible because you want people to feel a part of it.

"The majority of kids growing up in America remember reading the Guinness World Records. Without understanding miles or distance, knowing that someone breaking a Guinness record is something everyone can relate to. It just brought all sorts of positive attention."

During his record-shattering, seven-day run, Sheehy made time to meet with cancer survivors and shared Julie's story. Besides raising awareness in the community, Sheehy also raised $50,000 for the Leukemia & Lymphoma Society of San Diego, thanks in part to generous donors who heard why he was running.

To hit 408 miles — beating the previous Guinness record by 58 miles — Sheehy had to average running two marathons, and then some, every day for seven days. To reach his goal, Sheehy shaved his sleep time down to just five hours a night. He relied on a pace team to keep him going, and in spite of all the miles he put behind him, each leg of the journey was a challenge.

"Before each section, I would hope my legs would work," Sheehy says. "I would hold my breath and take that first step. And when everything worked after the first couple strides, I was relieved."

In the years since, Sheehy has focused on helping others in different ways. He's assisted runners in achieving their charitable goals, and helped them on their Guinness World Record attempts. In 2012, his plan was to complete all the Abbott World Marathon Majors in one calendar year, but his goal was thwarted when Hurricane Sandy cancelled the New York City Marathon. He shrugged it off and stayed in the city to assist with the aid efforts at Coney Island. And he opens up his three-bedroom downtown condo to cancer patients, their families and runners he met in San Diego who sometimes visit Chicago's renowned hospitals for treatment.

Guinness record or not, Sheehy isn't slowing down. He's got three races still on the books this year, as he tries again to complete all six Abbott World Marathon Majors races in a single year. He already holds a world record, so why does he keep running?

"It sounds silly," he says, "but to live life. You sign up to experience the challenge, to do something others won't do to see if you can. For me, it's about the self-exploration and the fun and adventure of it.

"I don't want to be that guy saying, 'I thought about doing this.' Just go do it."