Kris Stallenberg 60-min Z2 (Endurance) Medium #09 This endurance workout is punctuated by very short, sharp bursts of power. These 10-second efforts mimic accelerating over a small hill or briefly surging in a group. The key is to immediately settle back into your Zone 2 pace. This trains your ability to recover quickly from hard efforts while still in an aerobic state. While the bursts touch higher levels of the Coggan Power Zones, the overwhelming majority of the workout is focused on building Z2 endurance. bike