Consider we are trying to pre-acclimate for an expedition in Himalaya to shorten the actual timespan on site.

As an example, I am expecting a benefit if I go in the Alps for several days above 4000m and sleep over 3000m. If my trip to the big mountains like the Himalayas starts a week (or two) after that pre-tour am I still acclimated to some extent? If so are there approximations (maybe scientific studies) for how long the acclimatization benefit holds on and to what degree?

Edit to further explain the matter:

I am not asking the question because of a specific planned tour in Himalaya. I am interested in general, first to understand better how acclimatization really works and second to possibly shorten the (sometimes very expensive) acclimatization time. Of course it would be the best preparation to stay in Himalaya for a long time and acclimate slowly. But it should make a considerable difference if I am acclimated to my home-town at 500m or to 3500m. The question is how big this difference will be.

2 Answers 2


Altitude acclimatization is not just a single change in your body but a long list of different things that are going on. There is a nice chart on p. 326 of House and Johnston, Training for the New Alpinism, which gives a list of the following adaptations (they label #6 as two items):

  1. increased ventilation rate

  2. increased heart rate and blood pressure

  3. blood pH increases

  4. decrease in plasma volume

  5. increase in red blood cell mass and hemoglobin concentration

  6. decrease in size of muscle cells, and consequent increase in capillary density

  7. increased density of mitochondria

Your question is about how long it takes to lose the adaptation, but that doesn't seem to have been studied very thoroughly, so I'll start by relating the more well established information on how long it takes to gain the various adaptations and then circle back and try to answer your question somewhat. For each of the items above, House and Johnston give a "time for adaptation to begin" and a "time to end." I think the "time to end" means how long it takes until you're fully adapted. The time to begin is zero for 1-2, a few days for 3-4, hours for 5, and weeks for 6-7. The time to end is weeks to months for everything except 4, which is supposed to be complete in 1-2 days. #3 only happens above 5000 m, so you won't experience it at all from being at those altitudes in the Alps, but you can get the same effect by just taking acetazolamide (diamox).

OK, so what about de-acclimatization? House and Johnston have a short section about this on p. 358, titled "How fast do you de-acclimate?" It seems to be short because there's not a lot of solid evidence. In one study, people spent 16 days at 4000 m, then went to sea level for 7 days, and then went up to 4300 and were tested. "They were found to retain about 50% of their acclimatization." Unfortunately, House and Johnston don't give a reference to who did this study. I would like to know, e.g., by what measure the 50% is computed. In another study, called "Operation Everest III," the subjects lost their elevated hemoglobin levels in only 4 days.

So the evidence is obviously pretty scanty and not completely consistent. House and Johnson say:

When we examine our own experience, look at the historical record of high-altitude climbing, and ask others, we find that the most common rule of thumb is that you lose your adaptation to altitude at about the same rate as you gain it.

Everything I've said so far was general. You have a more specific trip in mind. The big question to ask would be how high you intend to go in the Himalayas and how long you intend to stay there. It seems like the necessary acclimatization time rises very quickly with altitude. For Kilimanjaro, at 5900 m, most people take about 7 days to acclimatize. House and Johnston give some sample acclimatization schedules for higher elevations. For Denali, at 6200 m, they show 18 days as normal, 10 as a "fast ascent." For people climbing to 8000 m, the schedules they show are all about a month. If you're going high in the Himalayas, then realistically you're going to need weeks to adapt, and compared to that, a few days spent in the Alps is probably not going to be significant.

  • 1
    Thx for those helpful infos. You are right it depends on the height difference. So I think it helps for Kilimanjaro and you could cut off some of the early acclimatization days when you are already used to approx. 4000m.
    – Wills
    Dec 28, 2014 at 9:13
  • Agree with @Ben here. If you're going high in the Himalayas, then realistically you're going to need weeks to adapt, and compared to that, a few days spent in the Alps is probably not going to be significant... +1!
    – WedaPashi
    Dec 29, 2014 at 6:05
  • Yes but what if I am only going to 6000m. We could also think of multiple tours in the Alps. How does my prior tours effect the recent acclimatization (like the answer of @Pepi)?
    – Wills
    Dec 29, 2014 at 9:00
  • I would suggest you rather spend time in the foothills of himalays(many of which are above 3000m). Also note that high altitude acclimatization is not a well defined science. What applies to @pepi might not work for you. You stand a better chance by spending more time in the Himalayas. Jan 2, 2015 at 5:04
  • 1
    And acclimatization mainly concerns with the red blood cells. And as far as my knowledge goes(which is quite limited), it takes weeks for red blood cell generation to be increased for higher altitude. A 3-4 day Alps trip will definitely not help. Neither will the repeated 3-4 day journeys. If you could spend around 10 days at 3000+, you stand a better chance. Also, 6000m is a lot. Don't underestimate it. If I may ask, where in Himalayas? Jan 2, 2015 at 5:16

Anecdotal evidence: my wife and I take periodic trips from a few hundred meters altitude to 3000-4000m (and sometimes over a pass at 4480m). We feel that going a little as one weekend per month provides a noticeable benefit. We've even camped in the same spot at ~3900m on a couple occasions and definitely slept better the second time.

  • I have observed similar effects in going from sea level to 3000m in the Sierra Nevada, however everything I've read in the science suggests that this effect is not observable in the research. I've no idea what to make of that. Dec 28, 2014 at 19:49
  • @Fred - possibly placebo effect.
    – user5330
    Dec 29, 2014 at 8:01
  • Honestly, I would not say that what you feel is due to your body having adjusted to the altitude. Muscle memory is not defined in high altitude adaptation. Most of the altitude sickness attributes to low oxygen content and which can only be offset using higher lung capacity (Even this cant guarantee anything). Hence taking two days a month trip doesn't really make any difference in your adaptation rate. Most probably as @mattnz indicated, it's the placebo effect and your mental preparedness that makes the difference. Jan 2, 2015 at 5:09
  • Lung capacity and red blood cell count. My bad I missed this. Jan 2, 2015 at 5:25
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    Maybe I should clarify that comfort was the only noticed improvement: better sleep, better appetite, fewer headaches. We still felt dizzy as the car went over the pass. Regardless of physiological changes, 'mental preparedness' is still a good thing.
    – Pepi
    Jan 2, 2015 at 6:21

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