Julian Romero didn't forget his shoes. He intended to run the Bank of America Chicago Marathon barefoot.

"It's really the most comfortable way to run, you know? Especially in heat like this, you don't have to have those socks and shoes on your feet, just have that cool air going over your feet the entire race," he told NBC Chicago.

A calm, unwinded Romero spoke with us moments after he ran 26.2 miles in about 3 hours Sunday morning.

Romero said he only decided to run on Friday, and bought his marathon registration number from another runner on Craigslist.

This isn't Romero's first barefoot marathon. He's run several marathons barefoot, including the 2007 L.A. Marathon.  The assistant professor at Purdue University  has also been featured on some blogs advocating barefoot running. 

"It's much better for your form," Romero said. "You really learn to run with much, I guess, better form, and land much softer on the ground."

Romero said his feet aren't even calloused from running barefoot on concrete and asphalt. "It's just like a 3-hour exfoliation," he said.