ExpeditionDan is absolutely correct.
It depends on what your definition of acclimatization is is.
Can you climb early on huffing and puffing not at your full athletic acclimatization and not suffer classic AMS symptoms like headache, nausea, etc. . Yes. Plenty of people do just that on Whitney with only one or two nights spent high first. Probably half. If they went back there after a week or two longer at elevation, they would find that they breathe easier, climb faster, and don't feel like they are pushing as hard.
The other half suffer BOTH the AMS symptoms and the aforementioned 'Mountaineers Foot."
Anyone who replies please do not get bogged down in statistics but rather the difference in physical presentations. Even the official definitions are not clear
Glad to see Harvey making this point. I have commented before about the dual function of acclimatization: staving off the worst symptoms, vs full (or even significant) athletic acclimatization. I think it is too often overlooked. I have not been able to find out whether Diamox, for example, has been found to help with the latter, but my subjective impression is that it help me a lot last year on the JMT. Felt rapid improvement and athletically acclimated after four trail days, coming from sea level to Yosemite Valley and starting the trail the next day. 5000, 9000 8500 and 9500' respectively the first four nights out of YV. Knocked my hydration all to hell for that period and two more days after, but that was probably due to wrong dosage(4x!) by my doc, and my not checking it till day 2.
