Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board How fast does the body "deacclimatize"?

Does anyone know how quickly the body begins to undo the effects of acclimatization when you descend? In other words, I understand that the body makes changes quickly the first few days, then the acclimatization slows but continues for weeks. Is it the same going down - do you lose most of the benefit right away, or does it last a while?

I ask because I'm considering trips about a week apart, but it would be nice if I can arrange my trips around my body's needs. Is there perhaps a curve that describes the rate each way?

z

do you live at sea level
are you planning day hikes on both occasions - to what altitude?

I was at 14k this weekend and my body is already hungering for more - but that is probably more psychological.
but I think you should benefit from getting back out so soon.

Going by memory here, but I seem to remember reading a long back-and-forth thread on this board during the past couple of years that addressed that question, and I think the final conclusion that came out of that discussion was that you lose the benefit of your acclimatization in approximately one week. If anyone else remembers that thread and wants to post the link, feel free.

CaT

this is a very complicated question.There are various portions of what acclimatization actually is made up of, so here are some very general responses in order of time. Others may disagree with the details, but these are some generalities.

Note that the first factor listed is probably the most important for the casual, short term sojourner to moderate altitudes like Whitney:

"reset pulmonary/ventilation sensors" change in days

tuned up somatic muscles will begin to detune in a week

polycythemia (more red blood cells, assuming you had been high enough and long enough to trigger this benefit) may last for a month.

intracellular factors may last for multiple months ( but these benefits would only have occurred in someone staying at high altitude for many, many months or even years)

genetic factors never change (unless also age-related)

sorry. no quick answer from a technical aspect. However, from the practical and personal perspective of many of us, I agree that only a few days or a week really begins to de-acclimatize you. In the medical literature, there is even a term called "re-entry" HAPE. Persons who descend are very soon at risk on re-ascension as if they had never gone high to begin with.

Hope this helps. Harvey

Easy answer.. Faster than you can "usually" get back to the mountains

I've been in the Sierra above 12,000' for several weekends in the past few months and I've come to the conclusion that I still feel well acclimated after one week away (I live in Socal at 1,000'). If I've been away for 2 weeks, I feel very little acclimated. Since Mt. Baldy (10,064') is close to where I live, I will make a quick trip up on the weekends between my Sierra trips to help prolong being acclimated. This seems to work well for me.

Anectodal comments:

I do think that things change as you age. I've gone thru three phases: at a young age, I was very susceptable to altitude problems. In the "middle," I could do no wrong and was rarely impacted by the symptoms of AMS. (Maybe I did enough high-altitude climbing that I never lost acclimitization?) Now ("tail end?"), things are back to the way they were when I was young.

As Mike stated, I also find that if I go to the High Sierra for a couple of weekends in a row, I'm fine on the next trip out. I would add that I'll feel even better the next time up if I've spent those prior weekends sleeping high. For me though, the trips up Baldy, or Baden-Powell, don't help and I'll be back at square one the next time up in the Sierra.

I'm hoping to use this strategy for an upcoming trip to China/Tibet/Nepal/India. Shortly after arriving in Beijing, I'm going to be riding a train that crosses a pass at over 16,500' on the way to Lhasa. In preparation, I'm planning on spending as many days as I can on the previous two weekends up in the High Sierra.

In answer to your question, in my case, I think I lose acclimitization somewhere in the 10-14 day timeframe.

Thanks for all the help so far. Here are some specifics:

When doing Whitney, I'm hoping to camp 3 days (the weekend prior to my trip)at about 6000'. I'd come back down on Monday, then on Thursday drive to Whitney and do it as a dayhike. Would the 3 days at altitude help, even though they ended 4 days before the trip?

I'm also thinking about staying at about 6000' for a few days before running the Long Beach Marathon. I'd come down to work, then go back up to sleep for 4 or 5 days prior to the marathon, then stay at sea level the night before the marathon.

The tricky part, as you can probably see, is to figure out if it will make any difference being either part time at altitude or coming down so long before the actual event.

Any further help or suggestions? Do the specifics shed any light?

z

The short answer is that 3 days at 6000 feet ending 4 days prior to your hike will not make much difference. Simplifying what was posted earlier, the two main acclimatization effects are 1) a shift in your hemoglobin (and myoglobin) oxygen association/disassociation curves that effectively make your body better at 'grabbing' the lower amounts of oxygen in the high altitude air and getting it to your cells. This happens in a few days, but it reverses just as quickly, so there won't be much residual effect 4 days later. The second change is an increase in the number of red cells, which happens much more slowly. So there won't be many extra red blood cells after only 3 days at 6000 feet to carry more oxygen to make much difference 4 days later.

An old rule of thumb that many climbers use is that you deacclimatize over the same number of days that you spend at high altitude. In your case, that would mean that 3 days down low reverse the effects of 3 days up high.

You should also note that 6000 feet doesn't acclimatize you for 14,000 feet, though it does get you going in the right direction.

This doesn't directly have to do with de-acclimatization but I thought it was interesting. It looks like you could do your math homework reasonably well on Whitney -- you just won't be able to do it for long because of the short attention span.

Mental ability expressed as a fraction of ability at sea-level for unacclimatized individuals (from McFarland14).

Altitude(m).....Visual sensitivity.....Attention span.....Short term memory.....Arithmetic ability.....Decision making ability
2500....................83%..................100%.................97%....................100%......................100%

3500....................67%...................83%.................91%....................95%........................98%

4200....................56%...................70%.................83%....................92%........................95%

5000....................48%...................57%.................76%....................86%........................90%

fascinating topic to my interest in brains at high altitude. thanks.

The McFarland reference must be from the Air Force studies.

Bottom line: both physical and mental incapacities at altitude can leave climber or pilot on/into the mountain!

So true. I met a guy ice climbing once who had led a medical expedition on Everest. One evening on Everest (in his tent in the mid twenties with a blood pO2 in the low 90's), the psychologist asked him over the radio to say all the words he could think of that started with the letter 'I'. This guy is a very smart cardiovascular surgeon, but in 60 seconds could only come up with one word: I. Both the physical exertion and hypoxia reduce your mental abilities when climbing high.

Recently, I read an article about a group who used an simple device to change the concentrations of oxygen and nitrogen that a pilot was breathing while flying a simulator. Their point was that 'going up' in an altitude chamber is a poor way of teaching pilots about their reaction to hypoxia. The simulator pilots showed significant degradation in their ability to execute complex procedures when hypoxic.

Sierra Sam pointed out that:

"You should also note that 6000 feet doesn't acclimatize you for 14,000 feet, though it does get you going in the right direction."

As I look again at the table above, it seems to point this out very well, in fact at 2500m (about 8000') it shows your impairment is minimal. But that makes me wonder why spending time at 8000' seems to help acclimatize at all. It appears that, for the unacclimatized, the brain at 8000' is close to meeting the "minimum requirement" and beyond that it's "downhill" from there on up (a twisted metaphor???).

I assume that spending time at altitude must change the chart for you. But I wonder if the chart would be "linear" in a mathematic sense. In other words, if going from 0 to 8000' gives you a 5% reduction in ability, then if you've acclimitized fully at 8000' and climbed to 16,000' would the reduction also be 5%? I assume this would depend on whether oxygen concentrations are linearly related to altitude (or is it exponential?). I looked for a chart showing oxygen concentrations at various altitudes but couldn't find one.

STOP HERE IF PHYSICS BORES YOU:

This is totally off topic but a related question for physics laymen to ponder in bed is: why do oxygen levels fall so drastically using sea level as a baseline? Aren't all particles drawn toward the earth's center of gravity (i.e., isn't the force of gravity related to the distance from the center of the earth, not the earth's surface?). If so, the distance from sea level to the earth's center is virtually the same as the distance from Mt. Whitney to the earth's center, in which case gravity can't directly explain oxygen depletion at altitude. In other words, all gas molecules don't smash into the earth like rocks do; but why do they float near the earth's surface but not far away? Is it due solely to temperature gradations causing different densities of gases? But if so, why is there oxygen at the poles? Inquiring minds want to know.

I don't thing this changes your arguments, but it's inversely related to the square of the distance from the center of the earth.

At the altitudes we are interested in, the atmosphere does not change composition much. Oxygen is 21% at sea level and on mountain tops. What changes is hte total pressure of the atmosphere.

Gravity does indeed point towards the center of the Earth and does not get noticeably weaker between sea level and 14000'. However, it does point down! That's why solid things fall until they come to rest on the Earth's surface, as we all know -- sometimes too well. Gases tend to expand to fill the available space, but gravity still concentrates them near the Earth's surface. An exponential dependence of atmospheric pressure on altitude follows from a constant gravitational force.

Thank you for the link, Calif.

If I understood all the articles, it appears that gravity gradations at hiking elevations don't play a significant part in oxygen depletion. It is mainly due to gradation differences in the "weight" (or pressure) of the gases pushing down on gases at lower levels. In other words, if you're at the top of a body pile, you don't feel pressure from above, but if you're at the bottom of the pile you are squished -- the difference between gravity at the top and the bottom of the pile is not why you are squished.

That statement is wrong. For example, a standard atmosphere is 760 Torr at 1 inch (or 1 foot) above sea level. If you double the altitude to 2 inches (or two feet), you obviously don't halve the pressure!

The dependence of pressure on elevation is approximately exponential. That means that the pressure falls by half every time you ascend a certain distance. I forget the number, but it's around 20000', so there is half as much oxygen (and nitrogen) at approximately 20000' elevation as there is at sea level.

Thank you again Alan -- you are obviously right and the quote is wrong (or I pulled it out of context). I deleted it from my post.

Dave, the difference of the gravitational force at see level and 14,000 feet has very little to do with the difference in atmospheric pressure at these two locations. What matters most is how much air mass is located on top of the measurement point. Compare this with water: If you dive to 10 meters below a lake’s surface the local pressure is going to be about 1 bar more than at the surface, irrespective of the altitude of the lake. Due the elasticity of air the relation between altitude and pressure is exponential, as opposed to the linear function in the case of the non-compressible water.

Near the equator the gravitational force is somewhat offset by the centrifugal force due the Earth’s rotation around its own axis. Thus, the resulting force pulling matter towards the center of the earth is larger at the poles. This results in higher atmospheric pressure.

Kurt