When races climb above 3,500 metres, a pattern often begins to emerge.
Athletes who grew up at altitude start to separate from the field. They are not always the most decorated names on the circuit, nor necessarily the fastest on technical descents. But in conditions of genuine hypoxic stress, they are operating much closer to home.
Understanding why changes how we think about preparation, pacing, and what is actually happening to the body when racing high in the mountains.
What Altitude Does to Performance
The percentage of oxygen in the air stays constant at any elevation — around 21%. What changes is barometric pressure.
As altitude increases, pressure drops. This reduces the force pushing oxygen into the bloodstream, meaning less oxygen reaches the working muscles with each breath. As a result, sustained aerobic output falls.
The impact is significant.
VO2 max begins to decline meaningfully above approximately 1,500 metres, with a drop of around 5 to 8 percent for every 1,000 metres gained. By 4,000 metres, a sea-level athlete may be working with 25 to 30 percent less aerobic capacity than they would have at home.
For skyrunning, where courses can spend extended periods above 3,000 metres, this often becomes one of the defining variables in a race.
Acclimatisation vs Adaptation
Athletes who spend days or weeks at altitude acclimatise.
Breathing rate increases, red blood cell production rises, and cardiac output shifts. These adjustments improve tolerance to hypoxia and can be extremely useful for racing at elevation.
But acclimatisation is temporary. Remove the altitude stimulus, and most of these benefits begin to reverse within weeks.
Chronic adaptation, built over years of living at elevation, is different.
Populations living at altitude — notably in places such as Nepal’s Himalayas, the Andes, and Iten in Kenya — show physiological characteristics that go beyond short-term acclimatisation. These may include greater lung capacity relative to body size, higher baseline haemoglobin levels, more efficient oxygen extraction at tissue level, and, in some populations, genetic variants that improve oxygen-binding efficiency.
The Pattern in Competition
José Manuel Quispe grew up in Ayanbasí, Peru, at above 3,800 metres.
He started competitive running in 2017 and entered his first skyrace in 2023. By conventional measures of athletic development, he was a late arrival. Yet in 2026, he leads the Merrell Skyrunner World Series standings after three wins from three, including victory at the Andes Mountain Skyrace — a course that tops out above 5,400 metres.
Blanca Llumiquinga of Ecuador won the women’s race at the same event in 2025. Rosalía Zegarra, Quispe’s training partner and a consistent podium finisher, is also Peruvian.
The pattern is not coincidence.
When the race climbs high, athletes from the Andes are not simply managing the altitude. They are racing in conditions that closely resemble their training environment.
Does the Advantage Reverse at Sea Level?
Partly.
Elevated haemoglobin levels can provide an aerobic benefit that transfers downward and persists for several weeks after returning to lower elevation. This is exactly why elite road runners and cyclists use altitude camps.
In that sense, an Andean athlete competing at sea level can retain a real physiological benefit.
But sea-level racing places different demands on the body.
Denser air allows higher absolute speeds, and athletes whose movement patterns are built around steep, technical mountain terrain do not always translate those strengths as readily to flatter courses.
European Merrell Skyrunner World Series races such as Calamorro, Gorges du Tarn, and Acantilados del Norte are technical and highly competitive, but they remain at relatively low altitude. The advantage is more evenly distributed there, and race dynamics depend more heavily on raw speed, climbing power, and descending skill.
What Sea-Level Runners Can Take From This
The full adaptation of a lifetime spent at altitude cannot be replicated.
Altitude camps help and may be worth considering before target races at elevation. But they are preparation, not transformation.
The more useful lesson is strategic.
At altitude, the gap between how you feel and how hard you are actually working can be deceptive. Hypoxic stress often registers more slowly than muscular fatigue. Runners who start a high-altitude race at sea-level effort can pay heavily in the second half — not because they lack fitness, but because they have spent capacity they did not have.
If high-altitude racing is a consistent goal, even short blocks of two to three weeks above 2,500 metres can help build tolerance and meaningfully reduce performance loss at elevation.
It will not entirely close the gap to an athlete raised at 3,800 metres.
But it can narrow it.
