He's run enough miles to circle the world five times, and a Minnesota man is now trying to set a long-distance record by running from coast to coast to raise awareness of autism spectrum disorders.
The current world record was set back in 1980, but if Steve Knowlton can average 70 miles a day at a pace of between 4-5 mph across 18 hours, he'll break it.
Knowlton already has 46 marathons and 11 ultramarathons under his belt, but this will still be a challenge. So far, the farthest he's ever run non-stop is 78 miles.
"I think the first two weeks are going to be the hardest," he predicted. "Two weeks at 70 miles a day will really be the key too."
After beginning to run at age 11, Knowlton finished his first marathon at age 13. Now, the 47-year-old is planning to run nearly three marathons a day.
"A lot of my training I do from Prior Lake to Mankato," Knowlton told FOX 9 News.
It's certainly ambitious, but it's also for a good cause. Knowlton hopes to raise money and awareness for those affected by Asperger's syndrome and autism along the 3,100-mile journey from San Francisco to New York.
"Basically, how to do it is go off into a daydream and don't really think about the pain I'm in or the circumstances," Knowlton said. "I've done it so much that it becomes more of a mind-over-matter than a physical challenge."
To set the record, Knowlton will have to make the trip in just 45 days. To get help with the mental training he'll need on the way, he turned to a friend and mentor who ran 75 marathons in 75 days, Terry Hitchcock.
"You've got to be convinced that you can put one more foot down and you can get through that day," Hitchcock explained.
This won't be Knowlton's first long-distance trek. Three years ago, he spent 100 days making a solo run from Seattle to Key West.
"When I got done, I didn't want it to end," he recalled. "I could have just kept running because it was such a freedom to go and experience seeing the country."
To fuel himself through the journey, he'll consume about 10,000 calories a day and still lose 20 pounds. He also anticipates running through 8 to 10 pairs of shoes.
Knowlton told FOX 9 News he has loved ones with Asperger's, and he's always wanted to do something to help. That drive is what Hitchcock believes will see him through.
"I think it's all right in his heart," he said. "He's ready to go."
The cross-country run will kick off on April 27, and Knowlton will need to top the Sierra Nevada mountain during the first three days -- but that's not deterring him or his supporters.
"You've got to believe him," said Theresa Namie. "It's his dream and we're behind him 100 percent, even if it is crazy."
Anyone who wants to donate to the cause or follow his record-setting attempt can do so online.