Altitude training and VO2max: what the science says

Endurance athletes have trained at altitude since the 1968 Mexico City Olympics made its effects impossible to ignore. The idea is simple: thin air forces the body to adapt, and those adaptations help back at sea level. The reality is more nuanced.

Why VO2max drops at altitude

The air at altitude contains the same 21% oxygen, but at lower pressure, so each breath delivers fewer oxygen molecules to the blood. Less oxygen bound to haemoglobin means less delivered to the muscles at maximal effort.

• VO2max falls as soon as you go up, and keeps falling the higher you go. In endurance athletes, the decline is roughly linear and starts at fairly modest altitudes; one study found a drop of about 6% for every 1,000 m.
• Well-trained athletes lose more than untrained people, partly because their very high cardiac output leaves less time for blood to pick up oxygen in the lungs.
• Performance in long events suffers, while short sprints are hardly affected — and can even benefit from the thinner air.

This is why race times at altitude are slower, and why hard sessions at altitude must be run slower than at sea level.

How the body adapts

Over days to weeks at altitude, the body responds:

1. Breathing increases within hours, and stays elevated.
2. Plasma volume drops in the first days, raising haemoglobin concentration without adding red cells.
3. The kidneys release more erythropoietin (EPO) within hours to days, stimulating the bone marrow.
4. Red cell mass and haemoglobin mass slowly rise — typically by a few percent over three to four weeks at moderate altitude, provided iron stores are adequate.

More haemoglobin mass means more oxygen-carrying capacity, which is the main route by which altitude could raise sea-level VO2max. See what limits VO2max for why oxygen delivery matters so much.

The catch: training quality

Living and training at altitude has a downside: because VO2max is lower, you cannot run as fast in hard sessions. Some athletes come home with more red cells but less speed.

"Live high, train low"

Levine and Stray-Gundersen (1997) tested a solution. Thirty-nine collegiate runners spent four weeks either:

• living and training at sea level,
• living and training at moderate altitude, or
• living at about 2,500 m but travelling down to about 1,250 m for training.

Both altitude-living groups increased red cell mass and VO2max. Only the live high, train low group improved its 5,000 m time at sea level, apparently because it gained the blood adaptations while keeping training speed. Later work from the same group found large individual differences: some athletes responded strongly, others hardly at all.

Since then, research has broadly supported "live high, train low" for well-trained athletes, with the benefit appearing to depend on spending enough hours at altitude each day — usually well over 12 — for three to four weeks. The size of the performance gain is debated and is likely small, often in the range of a few percent at most.

What it means for amateurs

Option	Likely benefit	Practical notes
Altitude camp (3–4 weeks)	Small, variable	Expensive; needs iron check, easier first week
Altitude tent at home	Small, variable	Needs many hours per night, for weeks
Short holiday at altitude	Little lasting VO2max effect	Adaptations fade within weeks of returning
Brief intermittent hypoxia	Unclear	Evidence is mixed
More consistent training	Large	Free and proven

For most recreational athletes, the gains from altitude are tiny compared with what a few months of consistent training offers. Start with the basics: 80/20 training and a weekly interval session such as the Norwegian 4×4, or follow a 12-week plan to improve VO2max.

Heat training is a cheaper alternative some athletes use. Repeated training in hot conditions expands plasma volume and improves heat tolerance, and some studies have reported performance gains in cooler conditions too, though results vary. It carries its own risks: build up gradually, drink enough, and stop if you feel dizzy or confused.

Safety

• Altitude illness — headache, nausea, poor sleep — is common above about 2,500 m. Ascend gradually and descend if symptoms worsen; confusion or breathlessness at rest needs urgent medical attention.
• Train easier in the first days, and expect a higher heart rate at any pace.
• Check iron stores before a long stay; low iron limits red cell production.
• If you have heart or lung disease, get medical advice before travelling to altitude or doing hard exercise there.

Tracking the effect

Watch VO2max estimates usually drop at altitude, because pace falls at the same heart rate, and recover after you return. Compare like with like, at sea level, using the same test before and after — see VO2max tests explained and the VO2max calculator, then check the VO2max chart.

Sources

• Levine BD, Stray-Gundersen J. "Living high-training low": effect of moderate-altitude acclimatization with low-altitude training on performance. J Appl Physiol, 1997.
• Chapman RF, Stray-Gundersen J, Levine BD. Individual variation in response to altitude training. J Appl Physiol, 1998.
• Wehrlin JP, Hallén J. Linear decrease in VO2max and performance with increasing altitude in endurance athletes. Eur J Appl Physiol, 2006.
• Gore CJ, et al. Altitude training and haemoglobin mass from the optimised carbon monoxide method: a meta-analysis. Br J Sports Med, 2013.
• Bonetti DL, Hopkins WG. Sea-level exercise performance following adaptation to hypoxia: a meta-analysis. Sports Med, 2009.
• Lorenzo S, et al. Heat acclimation improves exercise performance. J Appl Physiol, 2010.
• Luks AM, et al. Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness. Wilderness Environ Med, 2019.