Summary
Iñigo San Millán provides a masterclass on energy system pathways, fuel sources including lactate, the six zones of exercise training, and how Zone 2 training acts as both a diagnostic tool and treatment for mitochondrial and metabolic dysfunction.
Key Points
- Zone 2 is the intensity where lactate production equals clearance (~2 mmol/L)
- Zone 2 specifically targets mitochondrial function and fat oxidation
- Lactate is a fuel source, not a waste product
- Zone 2 training is diagnostic - reveals metabolic dysfunction
- Elite athletes spend 80%+ of training time in Zone 2
- Metabolic flexibility (switching fuel sources) improves with Zone 2
- Talk test: can hold conversation but prefer not to