Please remember to spread the word about this :(

Doesn't it only work if you then return to a lower altitude? I wonder how long the benefits last for.

Now that I think about it, I don't actually know how this even works. Well I know what I'm going to go read about next.

Edit: My findings:

• At high altitude, cardiac output (the overall rate of blood pumped by the heart) increases, largely due to increased heart rate. This increased heart rate reduces as one acclimatises to high altitude (though I'm unsure of if it returns to baseline. It appears to be complex, and at least somewhat differing person by person. These individual differences may explain why some people experience health problems at high altitude, beyond the initial ill feelings caused from first arriving somewhere that's high altitude)
• The stroke volume (volume of blood pumped by each beat of the heart) is lower at high altitudes. This does improve as one acclimatises, but not entirely. This seems to be affected by blood pressure stuff, such as reduced plasma volume at high altitude. It seems to be complex enough that we don't fully understand how the various regulatory stuff works.
• Most of the acclimatisation occurs by increasing the number of red blood cells in the blood. The hormone erythropoietin, which usually exists at a low level in non-hypoxic conditions, stimulates the production of new red blood cells. At high altitude, the level of erythropoietin in the blood rises to around 1000 times its baseline level. Increased production of red blood cells happens for a few weeks, by which point, there is enough to make up for lower oxygen levels at high altitude.
• When returning to low altitude, it appears that the changes back to the baseline happen over a similar timeline.

Tangential fun fact: a red blood cell has a lifetime of around 4 months. A single red blood cell travels around 400 miles before it is old enough to be recycled by the body.