Zone 2 (aerobic endurance)

Zone 2 is low-intensity aerobic endurance riding — in Coggan's power model, roughly 56–75% of FTP. Physiologically it sits at or below the first lactate/ventilatory threshold: an effort you can hold for hours and talk through in full sentences. It's the unglamorous zone where the bulk of most riders' base volume should live, because it drives the aerobic adaptations that raise your ceiling at very little fatigue cost.

Coggan Zone 2 ≈ 56–75% of FTP
    physiologically: at or below LT1 / VT1 (first threshold)
    'conversational' — full sentences, nasal breathing

'Zone 2' means different things in different systems, which trips people up. In Coggan's 7-zone power model it's the endurance zone (56–75% FTP). In Seiler's 3-zone physiological model the same easy riding is called Zone 1 (low-intensity, below VT1) — and confusingly, that model's 'Zone 2' is the moderate grey zone instead. This page uses the common cyclist meaning: easy aerobic endurance below the first threshold. What matters is the physiology, not the label.

Sustained low-intensity work is the primary driver of mitochondrial biogenesis and capillary density, improves the muscle's capacity to oxidize fat and spare glycogen, and expands plasma and blood volume and stroke volume — the aerobic base everything else is built on. It's trainable in high volume precisely because it's low-fatigue: you can accumulate many hours a week without needing days to recover from any single ride.

Zone 2 surged in popularity after Iñigo San Millán's work with WorldTour riders and his interviews describing its role in mitochondrial function and fat oxidation. The most common amateur mistake is riding it too hard — letting 'easy' creep up past 80% of FTP into the grey zone, which pays threshold-like fatigue for sub-threshold benefit and quietly undermines the next hard session. The discipline to keep easy genuinely easy is the entire point of the zone.