Had a real wake-up yesterday.
Not a strenuous workout. Eight hours of standing around...it was Range Day, I was in an AR-15 instruction course. Shooting, breakdown and cleaning. A lot of standing on the firing line at varying differences.
Holding a carbine. Not heavy at all.
The shocking thing was, after eight hours, I was literally beat to snot. It was frankly shocking...I used to work standing for eight hours, even on the railroad when covering for a switchman's position (it happens on short lines). That wasn't that long ago.
Just mentioning it, how little it can take to knock you out, if you don't stay on top of physical conditioning.
What you are describing is why it is CRUCIAL to keep up with maintaining your muscles.
Especially in older age.
It is a fact that once one gets into late 50's to 60 and beyond, muscle mass begins decreasing at a faster rate.
Tie that in with retirement where most people see a reduction in their physical activity, and it can accelerate.
Even just standing a lot in a job helps your muscles. It takes muscle use and constant balance just TO stand.
Sit down and all those muscles suddenly relax and no longer have to work to keep you upright.
Beyond walking and standing more, a good way to help strengthen your leg and ankle muscles indoors is to practice standing on one leg for a period of time. Then switch to other leg.
Then repeat a few times.
Soon as you do this, you will feel those muscles suddenly jump into action as they work to try to keep you standing upright.
Without work to do, muscles atrophy.
It's your job to prevent that from happening.
Now that you've gotten a wake up call on this, the question is, what are you going to do about it?
You can either let things continue to slide until the day comes when you'll need help getting up off the toilet, or you will find a way to keep those muscles strong so as to put off needing that help as long as possible.
Because that's really what it comes down to in old age. How long can you go without needing help to get up off of a toilet.
I don't know about you or anyone else, but I hope I never need that kind of help, because once you do, any independence you had, is long gone.
....and yes, I realize it's not realistic to never need that kind of help, but the farther you can push it closer to your final destination, the better off you will be.
Ie: better to only need that help for a short time at the end, than for the whole final decade of one's life, IMHO.