Well, rather than criticising Michael for feeling old I say Good On You for recognising early that things are slowing you down and considering how to ensure that doesn't continue while you are young enough and keen enough to do something about it.
My hubby is now 78 and never taken any notice of his body since he was about 20 and as a result his mobility is only a stone's throw away from being in a wheelchair. His posture is grossly stooped, he cannot bend his joints, has less strength than me (a 5-foot-three weakling), and simply doesn't care. Everything is too much effort/bother. Whilst I am not a lover of exercise, I am a member of a walking group (he stopped going cos he couldn't keep up with the 90-year-old leader), I deliver political leaflets regularly, and use a treadmill at home. I keep my brain exercised too, with daily puzzles of different kinds, quizzes, a cryptic crossword class, the household finances (he has never been interested in our 52 years of marriage), and as a retired accountant am Treasurer of local charities as well as auditor for a couple of others. Indeed, at 72 I've just landed a part-time job marking accounting exam papers. I'm also on the committee of three other local bodies.
I have suffered with scoliosis for 35 years but keep on top of it with floor exercises (getting up and down is a tad difficult now!) and eat healthily.
I have a close friend who has suffered RA for donkeys years and am impressed by her perseverance with keeping as fit as possible.
I might not live a long life cos nobody knows what might come along, but I am doing what I can to make the best of it while hubby does bu%%er all. I resent the likelihood that before long he will be totally immobile and I will be the one having to do everything for him.
So, Michael, good on you for recognising that old age is not something to be approached willy nilly and being prepared to ensure that you enjoy it as best you can.