The Physiology of Endurance Running Podcast Between Two Thresholds: Everything you need to know about Zone 3
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Jan 21, 2026 A deep dive into Zone 3, the heavy intensity domain between two physiological anchors. They unpack how lactate behaves and why heart rate and RPE help identify thresholds. Practical tips cover rep lengths, session pacing, and using races to estimate LT2. They also explore which adaptations Zone 3 best delivers and when higher intensity is needed.
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Dan’s 40k Day With Mixed Reps
- Dr Dan Osborn-Nash described a 40k day with mixed sessions including five-by-3k and mile reps off 90s rest.
- He felt the mixed metric sessions produced unexpectedly good paces and valued company for pushing efforts.
Rep Length Lets You Run Faster At Same Lactate
- Shorter reps allow faster speeds while producing the same lactate if you control rest.
- Manipulating rep length is a practical lever to recruit different fibres while staying in zone 3.
Estimate LT2 From Races And Time Trials
- Derive LT2 from well-paced races: use the average heart rate from ~50–70 minute maximal efforts.
- Compare multiple race distances to build a heart-rate profile across durations.