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Altitude training

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descriptionLiving high to thicken the blood and lift sea-level performance; the mechanism is sound and the haematology reliable, but the performance payoff in elites is genuinely contested.
tagstraining

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Altitude training

Evidence: contested

Living high raises haemoglobin mass; that much is reliable. Whether it delivers a real, worthwhile sea-level performance gain in trained runners is the contested part, with at least one placebo-controlled trial finding nothing. Near-universal use by elites is a signal worth weighing, not proof.

Altitude training means spending weeks living in the thin air of moderate altitude so the body makes more red blood cells, in the hope of racing faster back at sea level. The mechanism is not in dispute; the size of the performance benefit, and how much of it survives a proper control group, is one of the live arguments in endurance physiology.

The models, and which has the evidence

Three arrangements compete, and they are not equal.

  • Live high, train low (LHTL). Live at moderate altitude but descend to do the hard sessions. This is the best-supported model. In the founding trial, runners who lived at 2,500 m and trained at 1,250 m improved their 5,000 m time, while a group that both lived and trained high gained the same blood changes but did not get faster (Levine & Stray-Gundersen 1997). The lesson is that altitude degrades the pace you can hold in training, so training low protects the intensity that drives fitness.
  • Live high, train high (LHTH). The traditional altitude camp. The blood stimulus is real, but absolute training speed falls in the thin air, which partly cancels the gain. Results are inconsistent.
  • Live low, train high. Brief hypoxic sessions or sleeping in a tent while living and training at sea level. The hypoxic dose is too small to raise red cell mass, and meta-analysis finds no aerobic advantage over normal training, so this is the weakest of the three.

Two different "train low"s

“Train low” here means train at low altitude, the L in LHTL. It has nothing to do with the carbohydrate sense of training with low glycogen. The phrases collide; keep them apart.

The mechanism and the dose

Low oxygen drives the kidney to release erythropoietin (EPO), which stimulates the marrow to make red cells, raising haemoglobin mass and so the blood’s oxygen-carrying capacity. This pathway is textbook and secure. What it takes to trigger it is also reasonably well defined: roughly three to four weeks living above about 2,000 m, more than 12 hours a day, accumulating a few hundred hours of exposure. Across the controlled studies, haemoglobin mass rises by about 1.1% for every 100 hours of adequate hypoxia, with wide variation between people (Gore et al. 2013).

Altitude can be too low or too high. Runners who lived at 2,085 and 2,454 m improved at sea level; those at 1,780 m did not gain enough red cell mass, and those at 2,800 m got slower despite a large blood gain, because the higher altitude wrecked their training and sleep (Chapman et al. 2014). The practical living window is roughly 2,000 to 2,500 m.

The contested part: does it actually make you faster?

The blood change is reliable at the group level. The performance benefit is where the field splits.

The optimistic case rests on a meta-analysis estimating sea-level endurance gains around 4% for natural LHTL, in both sub-elite and elite athletes (Bonetti & Hopkins 2009). The figure is encouraging, but it leans on a statistical method that is itself disputed, and its elite estimate carries a confidence range that runs down through zero.

The sceptical case is harder to wave away. A double-blind, placebo-controlled LHTL study, the design that matters most, found nothing: no rise in haemoglobin mass, VO₂max, time-trial power or economy against a placebo group breathing normal air (Siebenmann et al. 2012). Reviewers in this camp argue that most of the supporting literature lacks placebo controls, uses small samples, and was not done in genuine elites, so the apparent benefit is partly expectation and publication bias (Lundby & Robach 2016). The pro-altitude side has published a rebuttal, so this is an open dispute rather than a settled refutation.

The honest summary: a real but modest sea-level benefit, commonly put near 1 to 2% for events of 7 to 20 minutes, is plausible and widely believed, but it is small relative to measurement noise and individual variation, and one rigorous controlled trial found none. The grade is contested.

Smoke where there may be fire

Almost every elite distance-running programme uses altitude camps, year after year, despite the thin controlled evidence. As with sodium bicarbonate, near-universal adoption by people whose careers depend on getting it right is a signal worth weighing, not proof. It could reflect a real effect the trials are too small and too placebo-prone to pin down; it could equally be tradition, the value of a focused training block away from distractions, and the fear of conceding an edge rivals are taking. The wiki weighs the adoption, without mistaking it for evidence.

Responders and non-responders

The average hides large individual variation. Splitting runners by their result, “responders” show a bigger EPO and red-cell response while “non-responders” gain little and tend to train worse in the thin air (Chapman, Stray-Gundersen & Levine 1998). Tempting as it is to label athletes this way, the label does not hold up: the same individual’s haemoglobin response barely correlates from one camp to the next, so the group mean repeats but the personal response does not, which is what regression to the mean and measurement error would predict. Treat “I’m a responder” with caution. This is one more case of individual variation that no measured trait reliably predicts.

In practice

If you camp at altitude

  • Fix iron first. Iron availability gates the whole response, and altitude worsens iron balance. Athletes who are iron-replete and supplemented gain red cell mass; the iron-deficient gain little (Govus et al. 2015). Screen ferritin before going and supplement on advice.
  • Live high, train low if you can. Do the quality sessions lower, or at least by effort rather than sea-level pace, because you cannot hold your normal speeds in the thin air at first.
  • Allow three to four weeks. Shorter blocks rarely accumulate enough hypoxic dose to move haemoglobin mass.
  • Expect disrupted sleep in the first days, and a higher risk of illness and overreaching from the combined hypoxic and training load. Altitude is a stress on top of training, not a free addition.
  • Race timing is uncertain. The blood gain persists a couple of weeks after descending, but de-acclimatisation pulls the other way, so the best day to race is individual and not well defined.

Heat training raises haemoglobin mass through a different route and is being explored as a substitute that avoids the travel and the training-intensity penalty; its performance payoff is similarly uncertain. See heat acclimation.

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