In this episode of the Critical Oxygen podcast, I am joined again by Dave Schell where we discuss field tests for determining training zones. We emphasize the importance of understanding the purpose of training zones and the physiological thresholds that bound them. We suggest using simple field tests to estimate zones, such as nose breathing or the talk test for zone 2, and iterative workouts or subjective efforts for threshold and VO2 max zones. We also highlight the need for consistency in workouts to track progress and avoid overcomplicating training.