Runaholic

One such woman complained, "My husband has become a 'runaholic'. He constantly talks about his running time, his equipment, people he has seen doing unusual things while he was running and on and on and on. […]

A "runaholic" might persist in running in spite of muscle aches, minor sprains, or more serious injuries; […]

First and last, I'm a runaholic. I started pounding the pavement right after my divorce.