Anaerobic threshold

The anaerobic threshold (AT) is the exercise intensity above which aerobic metabolism can no longer meet ATP demand and lactate begins to accumulate at a rate exceeding clearance; it corresponds approximately to the second lactate threshold (LT2) or the maximal lactate steady state (MLSS), typically 75–85% of VO2max in fit individuals. The term is mechanistically imprecise — lactate accumulation reflects an imbalance between production and clearance rather than an onset of anaerobic metabolism per se — and some authors prefer 'lactate threshold 2' or 'respiratory compensation point'. Sustained exercise at AT drives robust mitochondrial and cardiovascular adaptations; performance at or near AT is a strong predictor of endurance capacity and correlates with cardiovascular risk reduction.