I THOUGHT I might be in trouble when my very fit parkour teacher, Ben, told us he loved parkour because something always scares him. Then he announced the day’s theme: “High to low.” I started to ...

In a Beaverton studio encased by fake graffiti walls and a web of metal pipes, fitness devotees are pushing their bodies to their limits. But they're not running on treadmills or lifting weights.

The stone courtyard in downtown Denver, for this day, is an acrobat’s theater, a dance floor and an artist’s canvas. “Look at it. Some people see curbs, walls, concrete. I see a playground. A place to ...