Why Zone 2 Training Changed Everything
I spent two years training mostly in Zone 3-4 — the "comfortable but breathing hard" range that feels productive but isn't. My running pace improved slowly, my recovery between sessions was poor, and I often felt flat for races despite what looked like adequate preparation.
Zone 2 is the intensity at which you can hold a conversation — typically 60-75% of maximum heart rate, or below the first lactate threshold. It's boring. Sessions feel almost too easy. But the physiological adaptations are specific and powerful: mitochondrial density increases, fat oxidation efficiency improves, and cardiac output at submaximal effort grows.
The common mistake is drifting too high. A "Zone 2 run" that spends 30% of time in Zone 3 is mostly a Zone 3 run from a physiological perspective. I use FitPulse's distribution chart to audit sessions — if I spent more than 10% of time above my Zone 2 ceiling, I note it and adjust next session.
After eight months of 80% Zone 2 / 20% quality work, my easy pace improved 45 seconds per kilometre and my resting heart rate dropped from 58 to 47 bpm. More importantly, I recover between sessions in 24 hours instead of 48.