Guys, you have got to be doing something wrong. I'm 43 and I'm in great shape.
I studied dance for a while in college. The first thing they teach you in dance is how to dance for a lifetime (i.e., how to have a dance career that avoids slowly developing injuries.) It's a philosophy that thinks 30 years ahead.
I've lifted my entire life with the idea that I want to NOT cause little, unnoticable, slowly building injuries.
It doesn't have to happen.
If you guys are wrecked in your 20s... you are doing it wrong. Period.