Kris Stallenberg 120-min Z2 (Endurance) Medium #01 This classic endurance workout is designed to build aerobic base fitness. The main set consists of a long, unbroken interval in Zone 2. According to Coggan Power Zones, this intensity improves fat metabolism and muscular endurance without accumulating significant fatigue. Focus on maintaining a steady power output and a smooth, efficient pedal stroke throughout the entire block. bike