Kris Stallenberg 120-min Z2 (Endurance) Easy #08 This workout builds intensity progressively across three long blocks, all within zone Z2 (Endurance). You'll start at the lower end of the zone and finish at the top. This structure simulates the increasing effort required to maintain pace later in a long ride. It's a great session for building muscular endurance and aerobic fitness, based on the framework of Coggan Power Zones Level 2. bike