“Polarized Training Explained: Build an Aerobic Base and Boost High-Intensity Performance”

Polarized training, also known as the "80/20 rule," is a strategic approach to endurance training where the majority of your training time is dedicated to low-intensity exercise, while a smaller, but crucial, portion focuses on high-intensity efforts.
https://www.pacelinebikes.com/polarized-training-explained-build-an-aerobic-base-and-boost-high-intensity-performance/