Kris Stallenberg 90-min Z2 (Endurance) Pushing #02 This session uses 'over-under' intervals entirely within the endurance zone to improve your ability to handle subtle changes in pace and power. By fluctuating between the lower and upper ends of Z2 (Endurance), you'll enhance metabolic flexibility and fatigue resistance. This workout applies principles from the Coggan Power Zones to make steady-state endurance training more dynamic and challenging, simulating the varied demands of an outdoor ride. bike