Kris Stallenberg 45-min Z2 (Endurance) Medium #04 This workout, called 'Edge Play,' has you alternating between the top and bottom of your Zone 2. These frequent but small changes in effort improve your metabolic flexibility and ability to control power output. According to the Coggan Power Zones, spending time across the full range of a zone solidifies your fitness at that level. This session keeps you engaged and builds a robust endurance engine. bike