Kris Stallenberg 60-min Z5 (VO2 Max) Easy #08 This session introduces VO2 Max 'over-unders', where you alternate between a high VO2 Max power and a sub-threshold power. This challenges your body to clear lactate while still working hard, a key skill for racing and hard group rides. The goal is to build significant fatigue resistance at the top end of your fitness. bike