Elite endurance athletes have trained at altitude for decades, chasing a physiological adaptation that's hard to replicate any other way: more efficient oxygen delivery, driven by the body's response to a genuinely stressful environmental condition — reduced oxygen availability, or hypoxia.
The Core Physiology
At altitude, lower atmospheric oxygen pressure means each breath delivers less oxygen to your bloodstream. In response, the body ramps up production of erythropoietin (EPO), a hormone that stimulates red blood cell production, increasing your blood's oxygen-carrying capacity over one to several weeks of exposure. More red blood cells means more oxygen delivered to working muscles per heartbeat — a genuine, measurable endurance advantage once you return to sea level, at least for a limited window before the adaptation fades.
Live High, Train Low
The most well-supported modern protocol isn't simply "train at altitude" — it's "live high, train low": sleeping and resting at altitude to drive the EPO and red blood cell response, while doing actual hard training sessions at lower elevation where oxygen availability supports higher training intensity and quality. Training hard at altitude alone often backfires, since reduced oxygen limits how intensely you can actually train, potentially costing you more in training quality than you gain in adaptation.
Simulated Altitude Options
Real altitude exposure requires travel most people can't easily do, which is why altitude tents, masks, and hypoxic training rooms exist as substitutes. The evidence for these is more mixed than for genuine altitude exposure — altitude tents used only during sleep can produce some of the intended adaptation if used consistently for enough hours per night over several weeks, but training masks that restrict airflow during exercise are a different (and much less supported) mechanism entirely: they mostly train your respiratory muscles to work harder against resistance, not your blood's oxygen-carrying capacity, despite marketing that often implies otherwise.
Who Actually Benefits
The performance benefit from altitude training is most relevant to endurance athletes competing in aerobic events lasting many minutes to hours — distance running, cycling, cross-country skiing, rowing. It has little relevance for strength training, short sprint events, or general fitness goals, since the adaptation specifically targets oxygen delivery capacity that matters most in prolonged aerobic efforts.
The Real-World Tradeoffs
Genuine altitude training requires weeks of exposure (typically 3-4 weeks minimum) to produce meaningful adaptation, and the benefit fades within a couple of weeks of returning to sea level — timing a competition to land within that window is part of the strategy for athletes who use this seriously. It's also physically demanding: altitude exposure causes real fatigue and disrupted sleep initially, which is why the "live high, train low" split exists rather than just grinding through hard sessions at altitude.
The Bottom Line
Altitude training has a genuine, well-understood physiological mechanism and real competitive use among endurance athletes, but it's a serious undertaking with a narrow window of benefit — not something to bolt onto general fitness goals, and the popular training-mask shortcut doesn't deliver the same underlying adaptation as real hypoxic exposure.
