Think running a marathon is hard? Try 142 of them. In a row. Across the country.
That's exactly what Steve Knowlton did, starting out in Seattle and running straight through to Key Largo, Fla., averaging 37 miles each day -- 3,717 miles total -- through wind, rain, mountainous terrain and painful shin splints.
"There were some days I had to roll out of bed and crawl to the bathtub to loosen up my legs," Knowlton, 45, said from Florida, where he's vacationing with his family through Friday.
"It's all about your attitude and how you're going to deal with it," he said. "I had my good and bad days, but I just prayed God gave me the strength to get through each day."
It worked. The journey took the Prior Lake, Minn., resident through the treacherous Yakima Canyon, past what's billed as the world's largest ball of twine in Kansas, and into the Deep South, where he was routinely offered food and money by passersby thinking he was homeless.
He did it all in the name of research.
Knowlton was a high school athlete in his senior year when, at 17, he became seriously ill. He began dropping weight, plummeting from about 180 pounds to 132 pounds on his 6'3" frame. The doctors, he said, dismissed his symptoms as nerves about attending college in the fall.
Eventually, he was hospitalized. That was when Knowlton was diagnosed with Crohn's disease, a chronic inflammatory bowel disease.
"I had always been a very healthy and athletic kid and suddenly I had a permanent disease there was no cure for," he said.
A veteran of 43 marathons , Knowlton said that if he could raise both money and awareness for a cure, the arduous journey would be worth it.
"Just because you have Crohn's disease doesn't mean your life is over," he said. "My body held in there. I kept on a pretty good strict diet."
Knowlton said he picked his southeasterly route after seeing that most everyone else who had run across the country ran from California to the East Coast.
"I hadn't seen anybody who had ever diagonally crossed the United States," he said. "I thought that would be incredible because you'd see about every type of land and climate and culture during the route." "It was amazing all the different people I met."
After getting off to an ominous start -- reading in a newspaper that a camper had been attacked by a bear along his route and getting lost several times in the first few days -- Knowlton said he hit his stride.
Initially running with a large backpack that he thought made him look like "Santa Claus," Knowlton stopped at a Target on Day 6 to pick up a $100 baby jogging stroller to cart his gear.
And there were other mid-run adjustments. After finding that sticking to bike and jogging trails ate up too much time, and put him farther and farther off course, Knowlton's father made calls to several states before he entered to find out if he could run on the interstate shoulder.
They got a "yes" from Oregon, Idaho and Wyoming. He stuck to smaller roads the rest of the time. He tried to aim for 40 miles each day. Behind by two days by the time he reached the half-way point -- the aforementioned ball of twine -- he picked up his pace and, with the help of his father, re-routed himself.
Cross-Country Runner Got Repeatedly Mistaken for Homeless Man
Along the way he completed four days of 50 miles or more. And he often had visitors on the road in the form of police officers wondering why a man was running down the road with a stroller.
"I got pulled over probably 30-plus times because people would call in saying there was some guy pushing a little kid in a stroller out on the highway," he said. Soon, he knew just to stand patiently and hand them his driver's license. "I got it down to a science."
Other people he met, he said, were beyond friendly. Once he began running through the southern states, people would stop to hand him water, money and food.
"I don't know if they thought I was homeless, but it was pretty nice," he said.
In Arkansas, one woman "just pulled up in an SUV and handed me a bag and said 'this is lunch' and drove off. When he looked inside he found $10, her business card and a chicken sandwich.
He later called the woman to explain what he was doing and she was so enthusiastic she contacted her friends in Mobile, Ala., via Facebook and arranged for them to feed him when he ran through. She also reached out to friends in Florida to help Knowlton's mother arrange for his finish line victory.
And just as he was about ready to finish off his fifth pair of running shoes, a couple that pulled up beside him to find out what he was up to, went out and bought him a sixth pair to reach the finish.
But the kindness of strangers was not always enough to overcome the difficulties of the trip.
"There was always something that came up," he said, ticking off wind and rain and roads with no shoulders as common foes on the road.
He suffered through shin splints, weight loss and swollen ankles, vowing not to take the advice of others and rest even one day.
"I thought if I take one day off it might get easier to take days off," he said.
Dr. Linn Goldberg, head of the Oregon Health and Science University's Division of Health Promotion and Sports Medicine, said people who engage in such continued extreme exercise run the risk of not only injury, but reduced levels of testosterone in men, breakdown of muscles and inadequate hydration.
"This is not healthy, although that is not a problem in the U.S. with most people being overweight or obese and few getting enough exercise to impact their health," he wrote of Knowlton's run in an e-mail to ABC News. "It is not only an amazing feat, he must have amazing feet!"
It was a feat that seemed laughably unimaginable 25 years ago.
Decades Long Battle With Crohn's Disease Inspiration for 3,717-Mile Run
Ever since he was diagnosed with the disease as a teenager, Knowlton has endured years of illness, and countless what-ifs.
At 18, he underwent surgery to remove ulcers.
"I've never had to have surgery again, but within a couple of years after the surgery it came back," he said. In his 20s, after years of flare-up and constant worry, Knowlton said he took control.
"I said. 'I'm done ... having to worry about what I eat and every little thing I do. I just want to live like a normal person,'" he said.
Despite the need for a few rounds of steroids every so often to treat flare-ups, Knowlton said he's doing well.
He was cognizant, however, of the lack of privacy at many points in his route should he need to make a pit stop.
"I had a few problems during the run," he said. ""There was a lot of places where there was no trees or places to hide."
Knowlton, who kept a website and a blog updated during his run, said he has raised between $4,000 and $5,000 for the Crohn's and Colitis Foundation of America, (CCFA), and hopes the post-run attention he's been getting will lead to more.
"I probably set a record for the least amount of money donated to it," he joked.
CCFA spokeswoman Ariella Levine confirmed that Knowlton had contacted them about running for awareness, and that they helped him raise money through their half-marathon program.
"Every penny counts so we're happy to take whatever he's able to donate," she said. "It definitely was something that was different and out of the ordinary."
Knowlton, who was greeted in Key Largo on Saturday by his parents and girlfriend -- and a police escort as he ran over the final bridge -- has plans to relax until Friday and then board a plane back to Minnesota.