Trap 3 Raise

When your lower trap muscles are weak, retraction and depression of the scapulae is weak, your posture and performance is sub-par, and you've set yourself up for a future shoulder injury. The first way to fix this weakness is to make sure you're doing just as many (if not more) rows and pull-ups as chest and shoulder presses. But more specifically, make sure you're retracting and depressing the scapulae when you execute these exercises. Then, because this area is already behind developmentally, and will continue to lag behind, you need to actively strengthen it with isolated shoulder exercises that target the lower trap and rhomboids. – Mike Sheridan