Kris Stallenberg 90-min Z2 (Endurance) Pushing #03 Challenge your aerobic system with this workout featuring sustained Z2 (Endurance) efforts punctuated by short surges into the Tempo zone. These surges are designed to elevate heart rate and muscle recruitment briefly before settling back into an endurance pace, improving your ability to recover while still working. This method, based on Coggan Power Zones, builds a robust aerobic engine that can handle changes in pace without dipping into anaerobic reserves, crucial for long events. bike