Zone 2 (Z2) : foundational endurance
LoadThe intensity where you can hold a conversation without panting : your aerobic base.
Z2 sits around 60-75% of max HR or 65-75% of FTP. It's the prime intensity to build aerobic volume without paying a heavy recovery cost. Long weekend rides and runs (3-5h for an Ironman build) live in Z2 almost exclusively.
In TriPaced:
In TriPaced, the Z2 share is calibrated to the polarized 80/20 model: ~80% of total time in Z1-Z2, ~20% high intensity (Z4+). This ratio maximises progression without overtraining.
Source Seiler S., 2010 : What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes? (Int J Sports Physiol Perform)