I'm 42, 20 lbs. overweight, have little cartilege left and no ACL in either knee. A couple of years ago I spent a half hour every day pushing pretty hard on an elliptical in anticipation of the big trip and suffered a bit on the trail. Of course, that could have been due to a 45 lb. pack weight
Last year I did just about nothing to prepare and felt 100% better while only carrying about 33 lbs.
This year I won't get out there but will be hiking in the Winds for 11 or 12 nights so I'm back on the elliptical despite shedding another 4-5 lbs off my base weight ( I'm an admitted gear whore who spent significant amount of $$$ this winter/spring without telling his wife
) because of the significantly higher altitude. We'll be
starting roughly 1000' higher than we ever got in Glacier, hence the working out again.
So many mountains, so little time.