This Sunday, a stampede will take over the Las Vegas Strip. More than 30,000 spandex- and sneaker-clad runners will fly past casinos, Downtown landmarks and drunken tourists on the way to completing the fifth annual Rock ’n’ Roll Las Vegas Marathon and Half Marathon.

Weather and air-travel gods willing, Ron and Susan Carino will be among the crowd, though you’ll forgive them if they’re not weaving past slower runners or gunning for new personal records. When they leave the Strip start line Sunday evening, the Bay Area couple will be running their second half marathon of Nov. 17.

The Carinos will begin the day 1,200 miles away in San Antonio, where they’ll run the relatively flat 13.1-mile course of the Rock ’n’ Roll San Antonio half marathon. Then, it’s off to the airport, a quick flight to Vegas, a few hours' rest, a “run-thru” marriage vow renewal at the start line, three ... two ... one ... and run. Again.

The Carinos, who have completed 12 full marathons and dozens of halves, say it’s about trying something new. They aren’t too worried about the mileage; it’s the time in between the runs that poses a problem—legs may stiffen, muscles may get sore, energy may drain.

“We’ve been training both morning and evening with a lot of sitting in between to simulate the plane time,” Susan says. “We’ve never done this before, so it could be painful.”

If two half marathons in two cities in one day will be a fun adventure, their next big event is on a totally different scale. In January, the Carinos plan to run two full marathons in one week on two continents: the first in Antarctica, the second in Chile.

“We haven’t actually simulated the conditions quite yet,” Ron laughs, talking about replicating the Antarctic summer’s “balmy 30 degrees” and miles and miles of white.

“That one will be a challenge,” Susan says.