An indoor rock climbing gym in Brooklyn offers a great workout.

The athletes at Brooklyn Boulders in Gowanus range from pre-K to retirees.

Even experienced climbers can feel the workout burn.

"Rock climbing is the best workout I've ever gotten," says climber Arielle Hein. "When I'm in good climbing shape, it's the best shape I've ever been in. I feel like it's core, it's like your back, your legs, your arms."