Définition
The lactate threshold is the exercise intensity at which lactate production begins to exceed the body's ability to clear it, causing accumulation in the blood. Training at and near this threshold is one of the most effective methods for improving aerobic performance and metabolic fitness.
Lactate is produced in muscle cells whenever glycolysis outpaces oxidative phosphorylation — whenever glucose breakdown generates pyruvate faster than mitochondria can process it. This occurs at all exercise intensities, but at low intensities, the lactate produced is cleared as fast as it is generated. As intensity rises, there is an inflection point — the lactate threshold (LT1, also called the aerobic threshold) — beyond which lactate begins accumulating.
A second threshold (LT2, or the anaerobic threshold) marks the point where lactate clearance can no longer keep pace with production — the intensity at which fatigue onset becomes rapid. This roughly corresponds to race pace for well-trained athletes and marks the upper boundary of sustainable sustained effort.
Zone 2 training occurs at or slightly below LT1 — the intensity where lactate production and clearance are in balance. This is the primary zone for training fat oxidation and mitochondrial biogenesis. Training above LT1 (Zone 3 and above) produces more lactate, stimulates different adaptation pathways, and is appropriate for improving performance ceiling but not optimal as the primary training mode for health and longevity.
The lactate threshold is measurable through exercise testing — either formal lab testing (blood lactate draws at incremental intensities) or field protocols (the "talk test," heart rate based estimation). It is trainable: consistent Zone 2 work raises LT1 over months, meaning you can work harder while remaining in fat-burning mode — a hallmark of improved metabolic fitness.
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Ava Longevity · Built on the Ava Method · MMXXV