anacrusis - you say altitude, which is really interesting.. I have only been at high altitude once since my symptoms really got bad.. .. It was hot too, so I chalked it up to that.. but I almost got stuck walking in a square in Boulder since my hips just wouldn't work anymore! it was bad! The whole trip I was so weak!

And, if I think back since my 20's when I was hiking in altitude I could barely put one foot in front of the other, but I always thought I was just simply altitude intolerant! :0