Originally Posted by sjjohnston
As Woodee, Jim S, Mel Ratner and jstraw said, "We're talking about two different things here." Not to put words in others' mouths, but what ant said that is wrong was, "We are talking about the same thing."
At the risk of simply repeating what's already been said:
- One thing: altitude sickness.
- Another thing: being out of breath in thin air.
The former affects some people and not others for reasons that seem random, or at least aren't fully understood.
The latter affects everyone ... but if you're in better shape, you'll be better off when doing aerobic activities. That's true at any altitude, of course, but it may be more important at higher altitude, where your aerobic capacity (or lack thereof) limits you more than it does at lower altitudes.
1. At 10,000 feet, the reduction in the partial pressure of oxygen causes a combination of (A) less oxygen, and (B) less ability to use the oxygen present for those not acclimated. My understanding is that at 10,000 (might have been 11,000) feet, the hit from this combination is about 30% less useable oxygen than sea level.
2. Reaction to (1) is ideosyncratic, and has something to do with fitness and with something to do with genetics. Those two factors combine to dictate your VO2 max uptake. I'm in better shape than my brother, but when he and I go above 9,700 feet, he is less out of breath than I am.
3. If you have active asthma (as I do, sometimes) it can put you at serious risk when you add another over 30% hit to useable oxygen, to the point that a few years ago, I couldn't get my breath while propped up in bed at Keystone, because of the minor compression of the diaphram. (That after doing months of aggressive pre-season conditioning, including both aerobics and anaerobic threshold training.)