Kris Stallenberg 75-min Z2 (Endurance) Medium #07 This workout keeps the average power in Zone 2 but includes very short 'micro bursts' just above it. This helps improve your ability to respond to small accelerations while quickly returning to your aerobic pace. It's a dynamic take on endurance training that, while adhering to the principles of the Coggan Power Zones for Zone 2, adds a level of engagement and race-specific simulation. bike