Kris Stallenberg 90-min Z2 (Endurance) Easy #09 This workout enhances steady-state endurance with the addition of brief 'spin-ups'. The main effort remains in Z2 (Endurance) as defined by the Coggan Power Zones, perfect for building your aerobic engine. The short, high-cadence bursts are designed to activate fast-twitch muscle fibers and improve neuromuscular coordination without adding significant metabolic stress. Focus on staying smooth and controlled during these changes in cadence. bike