I'm fit. I run and I do lots of yoga, I'm surely stronger than most my age (55).
I had a box to move onto a shelf in a cupboard. I couldn't lift it enough to get my hands under it to eventry and lift it up iyswim.
I asked DS (22yo, with a manual job) to help, imagining it would be a two person job, and he lifted it like it was nothing.
I didn't like having my frailty demonstrated. I know people will tell me heavy weights are the way to go, but even so, this was a shock.