Running a marathon is difficult. It requires training and patience. Now imagine running 31 marathons.

Then, imagine running 31 marathons in 31 days. It sounds difficult, maybe even impossible. A Marine Corps veteran is doing just that, and he's doing it after losing both of his legs in combat.

Rob Jones is a retired Marine Corps sergeant. He was serving in Afghanistan when he stepped on an explosive. Both of his legs had to be amputated.

But that didn't stop him. Jones runs, bikes and rows on prosthetics. He competed in the 2012 Paralympics.

Courtesy Rob Jones Journey.
Courtesy Rob Jones Journey.

Now, he's running 31 marathons in 31 cities in 31 days. He started in London, and on Tuesday he took his journey to Denver.

Jones and his wife parked their RV at City Park early Tuesday morning. At 7 a.m., he started his 13th straight marathon.

Some folks ran with him. Others, including local veterans, stopped by the RV to say thank you.

"Most people see the marathon as a tough challenge," Jones said. "I figure I'll take that marathon and do it 31 days in a row for a full month, and that would just add insurmountable evidence to what I'm trying to say."

Jones says he wants his journey to show wounded veterans that they can overcome their injuries and live life to the fullest.

He's a double amputee, and yet, he's running more marathons this Fall than many can hope to run in a lifetime.

Courtesy Rob Jones Journey.
Courtesy Rob Jones Journey.

"Just because a veteran comes home wounded... some people might think that they are now broken and can't contribute to society anymore," Jones said. "I'm trying be an example of a wounded veteran who had a traumatic experience... and came back and was able to find a new way to stay in the fight and contribute."

Jones told 9NEWS he was surprised with how well he ran in Denver. He thought the elevation would slow him down. Instead, he said he made good time. It took him five hours to run the 26.2 miles.

Salt Lake City is the next stop on Jones' journey. And he's donating to veterans' charities along the way. You can follow Jones and make donations on his website.