The aerobic threshold (LT1) is the first inflection point in blood lactate, typically at 60-70% of VO2 max. Below LT1 is pure aerobic metabolism (Zone 1-2); above it, lactate begins to accumulate slightly but remains manageable. Training at and just below LT1 (Zone 2, conversational pace) builds aerobic base, mitochondrial density and fat oxidation capacity. Long-duration low-intensity training specifically targets the aerobic threshold and is the foundation of most endurance training models.
Key points
- First lactate inflection point (~60-70% VO2 max)
- Upper boundary of Zone 2 training
- Below: pure aerobic; above: slight lactate accumulation
- Zone 2 training raises aerobic threshold
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