Duration: 2 hours Target RPM: 85-90 RPE: 7/10 78-83% Max Heart Rate Overview Complete either on a trainer or outside on flat or undulating terrain Purpose Increase the efficiency of your body’s energy systems. Stimulates type 1 muscle fibers and mitochondrial growth, improves metabolic flexibility, and helps use fat and lactate substrates as fuel. Variations (Remove from plan) - Duration between 1.5 - 3 hours by increasing warm up and cool down periods. - Intervals can be 15m or 20m or 30m