originally posted by MikeOK
It's strange how it effects some and not others.
that's the main thing: it effects every person differently and being strong and fit doesn't really seem to have much effect - i.e. a really strong Cat 1 rider can feel like dirt at 10,000ft while a couch potato beer drinking weekend warrior can go to 14,000 and never feel any difference.
also, it affects different people differently at different times --- i know so many stories of seasoned mountain climbers who've been over 20,000ft many times without problems and then get sick at 11,000... although i've been in the 12,000 to 15,000ft range often with only mild headaches, my only real altitude effects were at only 9,000 to 10,000 ft (i was beat from a HARD mountain bike ride the day before and slept 2 hours in the back of my truck)