Kris Stallenberg 75-min Z2 (Endurance) Medium #01 This workout focuses on building a strong aerobic base with a sustained effort in your endurance zone. The main set is a long, steady block designed to improve metabolic efficiency and muscular endurance without accumulating significant fatigue. According to Coggan Power Zones, this Zone 2 effort is the foundation of all endurance performance. Focus on maintaining a smooth, consistent pedal stroke throughout. bike