The Physiology of Endurance Running Podcast Your guide to Zone 2!
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Jan 14, 2026 A deep dive into the controversy around Zone 2 training and why the term can be misleading. They unpack physiological definitions like LT1 and the problems with precise boundaries. Practical ways to estimate the zone in the field are shared, plus discussion of how easy volume builds mitochondrial and musculoskeletal resilience. They finish with programming tips and cautions about personalization.
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Use RPE And Heart-Rate Drift To Find Zone
- Use Rate of Perceived Exertion to find LT1: it's commonly about a 5/10 effort at threshold.
- Keep easy runs at ~2–4/10 RPE and watch heart-rate stability over an hour as a validation.
Watch Heart-Rate Behavior, Not Just Numbers
- Don't rely only on absolute HR percentages; check HR behaviour across multiple runs instead.
- If HR drifts upward during an evenly paced run, you're likely above LT1 and going too hard.
Zone 2 Helps Mitochondria But Isn't Always Optimal
- Zone 2 drives mitochondrial adaptations and improves fat oxidation, but it's not uniquely potent.
- Higher intensities (threshold, VO2max) often produce stronger adaptations per unit time.