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jschrock wrote:Oh...Rob I think we are talking about two different things. Length of time to acclimatize...and length of time for which the acclimatization lasts after the individual retuerns to low altitude.

I'm referring to the second. From your quote above it sounds like you are talking about the first.

I hear you, but my point is that for those of us who spend most of our time near sea level and get up to altitude for relatively brief periods, the adaptations made are different from those who are at higher altitudes for longer periods. Therefore, the amount of time to lose said adaptations is likely different. And I don't think anyone has actually answered the OP's question -- how long does it take to lose long-term acclimatization

rhyang wrote:

jschrock wrote:Oh...Rob I think we are talking about two different things. Length of time to acclimatize...and length of time for which the acclimatization lasts after the individual retuerns to low altitude.

I'm referring to the second. From your quote above it sounds like you are talking about the first.

I hear you, but my point is that for those of us who spend most of our time near sea level and get up to altitude for relatively brief periods, the adaptations made are different from those who are at higher altitudes for longer periods. Therefore, the amount of time to lose said adaptations is likely different. And I don't think anyone has actually answered the OP's question -- how long does it take to lose long-term acclimatization

Actually, I think we (you and me) sort of did. If it takes 3 weeks for the body to produce the extra red blood cells that provide "long-term acclimatization," then it possibly takes about 3 weks for the process to reverse itself. On the other hand, if the body does grow additional capillaries in response to lower air pressure, it's not likely that this "long-term acclimatization" would ever be lost.

Buz Groshong wrote:Actually, I think we (you and me) sort of did. If it takes 3 weeks for the body to produce the extra red blood cells that provide "long-term acclimatization," then it possibly takes about 3 weks for the process to reverse itself. On the other hand, if the body does grow additional capillaries in response to lower air pressure, it's not likely that this "long-term acclimatization" would ever be lost.

We would be taking guesses here though ... just saying "well, maybe" and "it's possible" without any evidence to back it up ..

For example, I don't get the impression that gain and loss of short-term acclimatization happens at the same rate. And I'm not sure if "additional capillaries" don't get broken down -- what happens when you gain and lose weight (talking about fat and muscle here, not fluid loss) for example ?

I'm not a doctor, and I don't even play one on TV

I was not expecting such a response on this! Thank you everyone, interesting to read each one and your thoughts about it.
I guess I always took my acclimation I had for granted after so many years..and did not really think about what would happen if I did not live at that elevation..I realize 6300 feet is not all that high compared to the higher parts of the Sierra...I have never had issues with altitude and always felt good above my 6300 to over 13k. But unfortunately it has now been over three years that I have been to anything over 10k

I guess I did not think after the 23 years I would loose it after only 2 months..that my body was so adjusted to that elevation...but I am not a doctor and so I really had no idea how quick one can loose that advantage.
I do believe living all those years at that elevation gave me the advantage of being able to feel okay at the higher spots..compared to if I lived at sea level.

I am sure not being in as good as shape as I was 3 years ago is not helping me either!
Thank you all again..I sure appreciate this..lots to think about!
Take care

jschrock wrote:Oh...Rob I think we are talking about two different things. Length of time to acclimatize...and length of time for which the acclimatization lasts after the individual retuerns to low altitude.

I'm referring to the second. From your quote above it sounds like you are talking about the first.

Anyway...this has about run its course...my eyes are glazing over now.

That's not the criteria we use here on SummitPost. Until expletives are hurled and someone's sexuality is questioned the discussion is not over!

There are many ways that your body acclimatizes, but the primary mechanism is an increase in the number of red blood cells.

When you move to a lower elevation, you will lose your acclimatization as your excess red blood cell mass naturally dies off as each cell reaches the end of its normal life cycle. The typical life span of a red blood cell is 120 days, so you will progressively "de-acclimatize" over a 120 day period.

If you return to altitude, you will regain your acclimatization at the same rate as everyone else, generally over a 3 week period.

There may be some permanent changes as the result of living at altitude for so many years (as noted above), but in comparison to the increase in red cell mass their effect is minimal.

Thank you Sierra Ledge Rat...makes more sense to me after reading all about it now.
Sure would be nice if we could keep those excess red blood cells inside of us!
Amazing how the body functions and what it can do.

Thanks again everyone!