All too many runners wear themselves out by running too fast too often—now more than ever. There is an obsession these days with high intensity. Most of the trendy new training systems are focused on speed work. Running magazines, Web sites, and books can’t say enough about the magical power of intervals. Even champion runners are more likely to credit their speed work instead of their easy running when interviewed after winning a race. Yet the typical elite runner does eight miles of easy running for every two miles of faster running.
