Done it a few times in life so far. Even now I’ll do a random set of wall pushups, do a run, do some heavy duty yardwork or cleaning. Make it a part of daily life somehow — doesn’t have to involve weights either.
There’s methods where you pit your muscles against each other. It can be done anywhere.
I’ve done weights and things but my FIRST exposure was this guy. It was old fashioned by the time I came along (he was already dead) but they were selling his course in the back of my Boys’ Life magazine.
Every week I got a new one You just pit your muscles against each other. There’s new names for it now. He called it “Dynamic Tension”. (some of his diet tips were weird though).
Anyway, it worked great. It’s all I had from 12-16 years old when I was finally allowed into a gym and could use weights. I still do some of it now and again when I think of it.
When you consider the physics of it it makes sense why it works.
Example: Let’s say you’re 150 lbs. You could lay on bench (relieving your mass from the equation) and do 150 lbs worth of weights.
Or you could use your own mass do use the 150 lbs you already carry with you.
Of course there’s a limit – your own body weight is the limit to such a system — but you can get pretty far with just that. At some point, weights are needed to go further. But whatever systems you use, it’s good to treat your body well.