View the Show Notes Page for This Episode Become a Member to Receive Exclusive Content Sign Up to Receive Peter's Weekly Newsletter In this "Ask Me Anything" (AMA) episode, Peter brings together his most up-to-date thinking on cardiorespiratory fitness into a single, practical guide designed to help listeners structure training for maximal impact on healthspan, lifespan, and long-term independence. He explains why cardiorespiratory fitness is one of the strongest modifiable predictors of longevity, clarifies what zone 2 training actually represents and how it differs from higher-intensity work, and addresses persistent confusion around exercise volume, intensity, and time constraints. The discussion covers how to measure and track progress in zone 2, VO₂ max targets and age-adjusted goals, planning for the marginal decade, and how to balance zone 2 with higher-intensity training across different weekly volumes. Peter also outlines how cardio training should be tailored for beginners, experienced trainees, and older adults, with special considerations for women and guidance on avoiding the most common cardio-training mistakes. If you're not a subscriber and are listening on a podcast player, you'll only be able to hear a preview of the AMA. If you're a subscriber, you can now listen to this full episode on your private RSS feed or our website at the AMA #79 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here. We discuss: Rational for discussing cardiorespiratory fitness, zone 2, and VO₂ max despite having covered the topic extensively [2:30]; Why cardiorespiratory fitness and VO₂ max are powerful and modifiable predictors of all-cause mortality compared with other health metrics [7:30]; How age-related declines in VO₂ max constrain healthspan and everyday physical function [12:30]; The cardiorespiratory fitness triangle: how different training intensities contribute to building the aerobic base, the aerobic peak, and overall aerobic capacity [14:15]; The cellular mechanics of cardiorespiratory fitness: mitochondria, lactate, muscle fiber recruitment, and intensity thresholds [18:45]; The debate over whether zone 2 training has unique benefits or whether higher-intensity exercise alone is sufficient [27:15]; Balancing intensity and sustainability as training volume increases, and the important role of zone 2 training [32:15]; How to identify your zone 2 training intensity [34:45]; How to measure and track improvements in zone 2 fitness [40:00]; How to accurately measure VO₂ max: lab testing, field tests, and the limits of wearables [45:15]; How to set meaningful VO₂ max targets based on age, sex, long-term decline, and desired physical capabilities later in life [51:15]; How to structure and execute a zone 2 workout [59:45]; How s