Kris Stallenberg 120-min Z2 (Endurance) Pushing #05 The 'Grinder' is a test of mental and physical endurance. This workout features a single, unbroken 90-minute block at a steady Z2 intensity. The goal is to build deep aerobic fitness, improve fuel utilization, and develop the mental fortitude required for long-distance cycling. According to Coggan Power Zones, this type of sustained effort is fundamental for improving your aerobic engine. Focus on consistency and form throughout. bike