The Growth Phase (Intermediate Level 1) An 18-week training plan aimed at the experienced endurance runner who is comfortable running five days per week. This plan is suitable for a runner who is accustomed to running an 8-10 mile long run before starting the plan and has completed several half marathons and/or a marathon at any pace. The Growth Phase plan is comprised of four mesocycles: base, strength, endurance speed, and taper. The primary outcome of this plan is to comfortably finish the ...