Zone 2
low-intensity aerobic training
The intensity at which you can hold a conversation — the foundation of endurance volume in every sport.
Zone 2 is roughly 60-70% of maximum heart rate, or 56-75% of FTP. The practical test is simpler than the numbers: you should be able to speak in full sentences. If you are snatching breaths every few words, you are going too hard.
Most plans rest on an 80/20 split — four-fifths of volume at low intensity, one-fifth high. That is not a fashion but an observation of how top endurance athletes actually train.
The commonest amateur mistake is doing easy sessions too fast and hard sessions too slow. The result is a week spent in the middle: too hard to recover from, too easy to drive adaptation.
What to do about it
- Use the talk test, not only the watch — heart rate lags and misleads in the heat.
- If staying in zone 2 means walking the hills, walk them. That is normal early on and passes within weeks.
- Do not shorten easy sessions to make them faster. Volume is the goal here; pace is only a constraint.
A common misconception
“Slow running teaches you to run slow.”
Low-intensity volume builds aerobic capacity, mitochondrial density and capillary networks — the base the fast sessions draw on. Without it, hard training has nothing to work with.
Related terms
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