I often see people recommending that their patients retract their scapulas during shoulder exercises to put the body in “proper posture.” Well, if you are not careful, you may run into a good amount of people that don't retract well and tend to shrug. This is again the upper trap dominance that we see so commonly. These people tend to pull their shoulders back and UP, not back and DOWN. A big difference.
Watch this video for an example. Notice that the person is shrugging while they retract. One simple technique that I do to correct this is to have the person just bilaterally externally rotate their shoulders (similar to the “W” exercise that I talk about in last years JOSPT article ) to get their shoulders back and down. This recruits the external rotators and the lower trapezius. Then hold this position and repeat the exercise. You can see the noticeable improvement in technique.