Zone 2
A moderate aerobic intensity you can sustain while holding a conversation.
Zone 2 is a training intensity roughly corresponding to the second of five heart-rate zones — comfortably aerobic, at an effort where you can still hold a conversation, below the point where lactate begins to accumulate rapidly.
It matters because large volumes of Zone 2 work build aerobic base, improve fat oxidation and mitochondrial function, and can be recovered from easily, making it a cornerstone of endurance training.
In practice, Zone 2 is estimated from heart-rate zones or the talk test, and forms the bulk of most well-structured endurance programmes.
Put it to use
Related terms
Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.
Last reviewed: