Kris Stallenberg 60-min Z2 (Endurance) Medium #05 This session introduces subtle variations within Zone 2 to keep you engaged. By alternating between the higher and lower ends of the zone, you'll improve your ability to control power output and handle slight changes in pace. This mimics the natural demands of rolling terrain. In the framework of Coggan Power Zones, this workout maximizes time in the most productive aerobic zone while breaking up the monotony of a single continuous effort. bike