
Altitude training comes down to one molecule and one journey: how oxygen gets from the outside air all the way into the mitochondria of the working muscle. Anyone who understands that journey understands why altitude works, why the gain is small and individual, and why the preparation begins weeks before the camp.
A great deal of mythology surrounds altitude training: "thin air", "less oxygen", "your blood gets thicker". These images are not wrong, but they are too crude to build training decisions on. The literature of the past 25 years keeps pointing to the same pattern: altitude acts on oxygen transport, the gain is modest (typically under 2% on sport-specific performance), and it differs greatly from athlete to athlete (Lundby, Millet & Calbet, 2012; Girard, Levine, Chapman & Wilber, 2023). To be able to steer that gain, you first have to see what happens physiologically the moment your runner starts living higher — not as isolated facts, but as one coherent journey from molecule to mitochondrion.
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