Kris Stallenberg 30-min Z2 (Endurance) Medium #05 Experience your endurance zone in a structured interval format. These short 'on' efforts at the top of Z2, followed by brief 'off' periods in lower Z2, help break up the monotony and improve focus. This session adheres to the Coggan Power Zones by keeping all efforts within the Z2 range to maximize aerobic adaptations without undue stress. bike