Agree with Don on Ron's post, nice summation
Ian, we must have very different ideas of what high level aikido is. Sorry about your popcorn.
Rob, slightly different question for you then - can you please name me one instructor who has a high level of skill in any martial art who hasn't also been known as being fit? Use of poor frail old Ueshiba isn't a good example as even in his later years he was still a fit frail old bugger. I honestly cannot think of a single decent instructor who has ever suggested you can be unfit or frail and still have a decent level of skill - technical expertise I'd grant you, but knowledge is different to application.
If I could ever find a martial art where training involved extreme couch potato methods while still being able to reach the "higher levels" I'd join like a shot.
Slurpy now in hand while continuing to read this fascinating thread...