Kris Stallenberg 30-min Z2 (Endurance) Pushing #06 This workout simulates rolling terrain by frequently alternating between the lower and upper ends of your Z2 (Endurance) zone. These constant but small shifts in power output improve your ability to respond to changes in gradient without leaving your aerobic zone. This type of training is a practical application of the Coggan Power Zones, preparing you for real-world riding conditions. bike