I have a client who has a concave/ convex chest since birth, basically one side caves in and the other is out, we are training with such exercises as bench press and shoulder press lat pull down and seated rows. he is concerned that one side will develop further and make the appearance even more pronounced. His right hand shoulder rotators are very weak also. any ideas would be greatly appreciated.
My first suggestion would be to avoid using any machines or barbells that allow him to compensate with this dominant side. You may also want to consider having his right shoulder girdle function evaluated by a qualified professional. As you mention in your question regarding his shoulder rotators, the visual difference in his chest could be an indicator of other muscle and joint issues in that region. For instance he may likely have problems with scapular stabilization on that same side as well. These issues may even expand beyond the shoulder girdle to the other anatomical slings that work in cooperation with the pecs.
If his condition is congenital (born with it) and his body is deficient muscularly and/or neurologically, there is still plenty of opportunity to maximize the capabilities he has and to avoid compounding any altered movement patterns he has developed over the years.
With a thorough assessment of his shoulder girdle, you can formulate a plan for correcting imbalances and reinforcing proper movement patterns. Upper extremity exercises should be done with dumbbells and independent cables for each side. Provide an environment that demands each side work with within its capabilities.
Finally, remind your client that the aesthetic differences in size are created by muscle hypertrophy. And the amount of hypertrophy is significantly dependent on the quality and quantity of caloric intake and not just resistance training.
Anthony B. Carey M.A., CSCS, CES