If you are involved in weight training and you start to encounter that one side of your body is lagging when doing a shoulder press, doing a biceps curl or the chest press, then yes there are some weaknesses.
The one thing that fitness professional do not realize is that they also need to strengthen the muscles that support the shoulder girdle and that is where these discrepancies can become prevalent. The easiest advice that we can give is start incorporating rotator cuff muscles to work the SITS muscles. In addition, start adding in some shrugs but also practice some scapular exercises to really strengthen that part of the back and shoulder girdle. If you need more help with this contact your physician, physical therapist and/or Portland personal trainer. If you are in therapy for this, when you are released make sure they write a prescription on what they want you to continue to do.