Travelers can admire, but not ride, the ten art-bikes currently displayed on top of baggage carousels at Denver International Airport.

But at Philadelphia International Airport passengers can work off some of the calories consumed in the food courts by riding stationary exercise bikes scattered throughout the terminals.

“I was actually looking for an electrical outlet,” said 62-year-old Tom Currie, who was biking while on a three hour layover at PHL last Friday afternoon on his way from San Diego to Rome. “But the bikes are right next to the outlets, so I figured this was a good way to get some exercise instead of sitting around.”

As part of its summer-long Just Plane Fun customer appreciation program, PHL recently replaced a few of its popular rocking chairs in the shopping area between concourses with several hands-free exercise bikes.

Eight additional pieces of low-impact exercise equipment were bundled into a fitness zone that pops up at a different location in the airport every two weeks.

“It’s easy to stiffen up on short or long flights, but even light cardio exercise that doesn’t work up a sweat can help travelers stay loose,” said Rich Hebert, a frequent traveler and the CEO of Smooth Fitness. The fitness equipment manufacturer is based in a Philadelphia suburb and donated the equipment for the summer-program to PHL airport.

Working out at PHL was such an immediate hit that there are now 30 exercise bikes in the terminals. Airport officials are also discussing how to allot equipment maintenance and replacement funds to make the temporary program a permanent fixture.

“Traveling to and through airports is stressful for many people and our job is to make that experience less stressful and more enjoyable,” said James Tyrrell, PHL Deputy Director of Aviation. “This exercise equipment helps us meet that goal. And so far, response in social media and elsewhere has been off the hook.”

While spas and other wellness amenities are no longer rare at airports, “what’s new about the ‘Fitness Zones’ at Philadelphia International Airport is that they bring the gym directly to the concourse, encouraging easy access and low-impact exercise for everyone in the vicinity,” said Kevin M. Burke, president and CEO of ACI-NA, which represents most North American airports.

Working on their own or with the American Heart Association, many airports have created walking paths both inside and outside the terminals. In many cities, there are also bike paths to and from the airports. And there are now yoga rooms, usually with loaner mats, at airports in San Francisco, Dallas/Fort Worth, Chicago and Burlington, Vt.

Toronto Pearson International Airport has a 10,000-square-foot GoodLife Fitness club inside the terminal and on-property hotels at some airports offer reasonably-priced day passes to airline passengers with long layovers who want access to fitness and spa areas. Examples include the Hilton Chicago O’Hare Airport, The Westin Detroit Airport, the Grand Hyatt DFW and the Fairmont Vancouver Airport.

(My story about working out at Philadelphia International Airport first appeared on NBC News Travel in slightly different form.)