6 A.M. With...Dan Reynolds

Six days a week, the Imagine Dragons frontman battles his demons (physical and otherwise) by pushing his body to the edge.

- By Andrew Heffernan, C.S.C.S.

Dan Reynolds is running for his life.

You wouldn't know it from his leisurely pace. Striding along on an AssaultRunner treadmill at a storefront gym on the Pacific Coast Highway, the six-foot-four, 205-pound singer looks calm and relaxed. To a guy who works out six days a week, moves like Jagger two hours a night to capacity crowds, and dunks basketballs for goofs, today's run (a warmup for an intense weights session that will rock his legs, shoulders, and stamina) barely registers as a workout.

Still, for the 35-year-old musician, it's a lifesaver. Reynolds has been dogged by chronic inflammation. In his early twenties, he developed ulcerative colitis, which threatens to turn his guts into coiled knots of pain. Then, at 23, he was diagnosed with ankylosing spondylitis (AS), a second, rarer inflammatory condition that affects the spine, pelvis, and digestive tract. Untreated, it can lead to vision loss, fusion of the vertebrae, and cardiovascular disease.

The standard treatment for these conditions is fistfuls of immune-suppressing drugs, which sap Reynolds's strength and leave him vulnerable to colds, flu, and sinus infections-disastrous for a guy whose career depends on his rock-tenor falsetto. The only alternative? An ultraclean diet and lots of exercise.