Slapstick Knights

The news sent a seismic shiver through the film world: "Jackie Chan admits he doesn't do all his own stunts." A few weeks ago, the universe's top action star acknowledged that, if a movie requires him to "ride an F-16 jet fighter, or to jump over a series of hurdles with a crazy horse, or to perform two 720-degree somersaults," he will hand the job to a younger daredevil. "But one somersault, I'll do it myself."

Jackie is just 48, but in stuntman years that's about 90. He has been punishing his body, and vice versa,...