Long-distance runs across the United States are nothing new—heck, Patrick Sweeney and “Barefoot” Alex Ramsey did one earlier this year; Ramsey going from Huntington Beach, Calif., to Washington D.C., and Sweeney extending the journey to Boston.

But this one is a little different. Sweeney and Ramsey plan to run the Chicago Marathon on Sunday, then start an 850-mile running journey to New York City, with plans to get there in time to run the New York City Marathon on Nov. 1. That’s 21 days of running 40-plus miles a day, with two World Marathon Majors races on each end. And with the New York City Marathon start time set in stone, Ramsey and Sweeney have a hard deadline they have to meet.

“We’re also jumping right into high mileage,” Sweeney said. “I run every day, but I don’t run that much. But the body is great at adapting.”

Sweeney and Ramsey are doing the run as a U.S. leg of the Champions Walk for Peace, which was set up to bring awareness to ethnic violence in Kenya’s North Rift Valley.

The two are certainly cut out for the job. Sweeney is a 2:37 marathoner who says he runs about 20 ultramarathons a year on average. He also has a Guinness World Record for a 24-hour run on soft sand, covering 94 miles.

Ramsey, meanwhile, has qualified for the Boston Marathon running barefoot, and has run the Leadville Trail 100 among other high-profile ultras.

Both runners are ambassadors for Luna Sandals, a minimalist footwear brand co-founded by Barefoot Ted of Born to Run fame.

The two are good friends, which will make the journey easier for both.

“Alex is one of the most easygoing, mellow, positive people I know,” Sweeney said. “I love being around positive people.”

Sweeney and Ramsey will make a relatively straight shot from Chicago to New York, passing through Indiana, Ohio, Pennsylvania and New Jersey.