Kris Stallenberg 75-min Z2 (Endurance) Medium #04 Push the upper limits of your endurance zone with this interval-based workout. By targeting the higher end of Zone 2 in the Coggan Power Zones framework, you'll build 'aerobic durability'—the ability to sustain a strong pace for a long time. The short recoveries keep the pressure on, simulating the demands of a long, steady group ride. bike