Sometimes a move hurts my joints, like pressing “hurts” my shoulders. Pain during the lift, for hours after the workout and for the next day or two. This is “bad” and I might take the lift out.
Other times a move “Trains” my joints. There is some discomfort during the lift, but no sharp pain. Then the discomfort fades over the evening, and is totally gone the next morning. This is “good” and I might keep the move in.
It’s also possible that the lift is OK, but I mess up the first time I do too much volume. Like I did 5 sets of 20 front delt raises and it didn’t hurt while I was in the gym, but then my shoulders were fucked up for a week and a half. The next time I was more cautious did 3 x 12, and had no problems.
The lifts can also be OK, but you just do too many lifts. Like overhead pressing and floor pressing are both “Big,” “Compound” lifts. Maybe if you only did 1 “big” lift your shoulders would be OK. But doing the 2nd big lift smashes them.