Does altitude training actually work?
Yes, but less straightforwardly than the popular account suggests — and the most effective protocol is the opposite of simply moving somewhere high.
The physiological basis. At altitude, air pressure is lower, so each breath delivers less oxygen. The body responds by producing erythropoietin (EPO), which stimulates the production of more red blood cells. More red cells means greater oxygen-carrying capacity, which should improve endurance performance once the athlete returns to sea level.
Other adaptations occur too — changes in capillary density, buffering capacity and muscle efficiency — and their relative contribution is debated.
The problem with simply training at altitude. You cannot train as hard. Reduced oxygen availability means lower absolute training intensity, so while the blood adapts, the training stimulus is diminished. Athletes can lose fitness in the qualities that require high-intensity work, offsetting the haematological gain.
The solution: live high, train low. Spend the majority of the day at altitude — sleeping and resting — to drive the adaptation, then descend to train so that intensity is preserved. Research led by Benjamin Levine and James Stray-Gundersen established this approach, and it remains the model with the strongest evidence.
Practical implementations: living at altitude and driving down to train; altitude tents or houses that reduce oxygen concentration artificially while allowing normal training outside; and normobaric hypoxic chambers.
The complications:
Responders and non-responders. Individuals vary substantially in how much EPO and red cell mass they produce, and a meaningful proportion gain little. This is genuine and not fully explained.
Iron status is limiting. Producing red cells requires iron, and athletes who are deficient adapt poorly — so iron assessment is a standard precondition.
Dose and duration. Adaptation requires several weeks at sufficient altitude, and too high causes sleep disruption, appetite loss and impaired recovery.
Timing of return matters, and the optimal window after descent is debated.
The evidence base is weaker than the practice. Altitude training is near-universal among elite endurance athletes, while controlled studies have produced mixed results, partly because properly blinded studies are extremely difficult to conduct.