Kris Stallenberg 45-min Z2 (Endurance) Easy #10 This workout features descending interval lengths, starting with the longest and most challenging block first. This 'front-loaded' approach builds fatigue resistance and mental strength. By tackling the hardest part when you are freshest, you ensure a high-quality effort. This structure, based on Coggan Power Zones, is an effective way to accumulate time in zone and boost your aerobic base. bike