I agree that it is a matter of poor posture. Sometimes when we tell a client to move or stand a certain way, they just don’t get it because they have never “felt” what good posture feels like. Therefore they can’t imitate it. I try to get them to feel the sensation in a couple different ways. Instead of showing them how I want them to lift or stand, I show them the incorrect way and then the correct way. When they can’t feel what is right in their body, they can see the contrast in what I am showing them. To give them the sensation, I have them stand with arms straight out in front a little higher than shoulder level. Then just pull the shoulders toward the back. Then arc the arms as they come down to the sides. They will feel their shoulder blades fit into pockets. Let them know that is how they should be standing. Another is to have them hold 10# or above dumbbells with hands down by their sides. Show them the exaggerated move of rolling the shoulders back and down and let the weight of the dumbbells hold them in that position. While in the position have them extend the back of the neck. Can tell them it’s like a string pulling up on the crown of their head or try to give themselves a double chin. Let them hold this position up to a minute, then release and repeat a couple of times. Use the foam roller after every session. Have them lay on the foam roller and drape their shoulders open and hands on the mat. If they can’t find the release, massage the shoulders open. Then each time they begin a lift where they tense up, stop them, have them get into good posture first and then lift. If they have felt the sensation of what it should feel like they will then get it and after awhile they will begin to self-correct. Yoga and pilates also reaffirm these good posture habits.