I'm in my 50s, lifting weights for about 3 years now, slow steady increases in weight and am much stronger than I was in 2019. Recently while bench pressing I felt something "pop" in my shoulder and now can't do any pressing movement at all without significant pain. Diagnosed and tried to rehab it as a tendon strain with no improvement. Getting an MRI soon to see what's going on.
At my age I don't really feel "old" mentally or physically, so hitting my body's physical limits in the gym is both difficult to accept and discouraging, as I had been making decent progress up until then. I can still squat and deadlift and do many other accessories but I am paying much more attention to what my joints and ligaments are telling me.
Pushing weights continuously, in higher age, will eventually lead to injury, even if muscles would easily go even further, they are much better at repairing/building up quickly compared to ie tendons or ligaments. Even for young, there is general advice to put 1 week out of ie 10/12 of complete rest, or probably active rest. It is for all those little fractures and sprains in connective tissue to heal a bit. With age, this should be more frequent and/or longer and as usually everything is very individual.
I’ve always thought it’s because they don’t have very much muscle to begin with, that braking a leg or something, forces you to be still so much that you loose whatever muscle you do have left. That in turn has other negative effects; socially from not going out of your house, maybe even cardiovascularly, mentally, etc.
That’s how it’s been for my grandmother, and for my wife’s grandparents. Purely anecdotal.