Kris Stallenberg 30-min Z2 (Endurance) Easy #02 This session introduces gentle variations in intensity to improve aerobic fitness without causing significant stress. By alternating between the lower and upper ends of your Z2 (Endurance) range, as defined by the Coggan Power Zones, you'll challenge your body to adapt to subtle changes in effort. This helps break the monotony of a single-paced ride while keeping the focus firmly on building endurance. bike