Andrew Johnson is a two time US Olympian in Cross-country skiing and an assistant coach at the University of Utah. He recently launched a personal coaching service. For more information, visit http://www.xccoachaj.com or email Andrew at info@xccoahaj.com When should I start doing intervals? When should I start adding level 4 intervals? How often should I do intervals? These are all questions I hear fairly often and they are questions that don’t have simple answers. Intensity,...