Yeah, a lot of those guys are a bit rough on themselves too, some work harder, some work smarter... Some can't be bothered to ask for help lifting stuff that should two guys should do, etc...
I don't know what I learned in HS phys ed, but I don't remember basic lessons on how to take care of your body.. Stuff like diet, stretching, basic strength exercises. The guys I know who do physical labor into their 50-60's take care of themselves and are in better shape, injury wise, than guys doing desk jobs or trucking.