The practice of altitude training has been a cornerstone of endurance sport preparation since the 1968 Mexico City Olympics forced coaches to confront the performance effects of reduced oxygen availability. The fundamental mechanism is straightforward: sustained exposure to lower partial pressures of oxygen triggers an increase in erythropoietin production, which in turn stimulates red blood cell synthesis. More red blood cells means greater oxygen-carrying capacity, which translates directly into improved aerobic performance at sea level.
The "live high, train low" model — sleeping at altitude while completing key training sessions at or near sea level — has emerged as the dominant approach over the past two decades. The rationale is that sleeping at 2,000 to 2,500 meters provides sufficient hypoxic stimulus to drive hematological adaptation, while training at lower elevation allows athletes to maintain the intensity and power output that altitude would otherwise limit. Athletes typically need a minimum of 14 consecutive nights at altitude before measurable changes in hemoglobin mass become apparent.
Individual response to altitude varies considerably, and this is the aspect most frequently underestimated in coaching programs. Roughly 50% of athletes respond well to altitude camps, showing a 3–5% improvement in VO2max after a standard 3-week block. About 25% show a modest response that may or may not translate to race performance, and the remaining 25% show no measurable benefit — or in some cases, a temporary performance decrement from the accumulated fatigue of altitude exposure. Genetic factors, particularly variants in the HIF-1α and EPO genes, explain much of this variation.
The nutrition demands of altitude training are consistently underappreciated. Iron availability is the rate-limiting factor in new red blood cell production, and athletes who arrive at altitude with suboptimal ferritin stores will blunt or eliminate the hematological response entirely. Current recommendations call for ferritin levels above 40 μg/L before beginning an altitude block, with daily supplementation of 100–200mg of elemental iron for athletes below this threshold. Caloric needs also increase at altitude — resting metabolic rate rises by approximately 5–7% in the first week — and athletes who fail to compensate often lose lean mass, undermining the very adaptation they are pursuing.
Simulated altitude through nitrogen-dilution systems or hypoxic tents offers an accessible alternative for athletes who cannot relocate to mountain training centers. These systems can achieve equivalent inspired oxygen fractions to natural altitude, and studies comparing natural versus simulated altitude show comparable hematological responses when exposure duration and oxygen levels are matched. The primary disadvantage is cost and the psychological burden of sleeping in an enclosed tent, which some athletes find disrupts sleep quality — a critical factor in recovery and adaptation.