As an athletic individual I find myself wondering as to why I seem to have more muscle fibers attached from my left pectoral minor and major muscles to shoulder and ribcage , while my right side being more dominant has less muscle fibers and causes some discomfort for me when I flex the right pectoral muscle in fixation as to when I flex my left pectoral muscle I feel perfectly fine and can feel the actual muscle as it expands due to the force exerted. I am aware as an aspiring medical student that this question is silly, but I’ve contacted many sports medicine specialists who’ve simply repeated to me that I should workout my right pectoral muscle more and to perform more repetitions which has done absolutely nothing in the past 6 months, I’ve also noted that my right pectoral muscle is somewhat thin compared to my left pectoral muscle (the area attached from the muscle its self to my anterior deltoid). I had been diagnosed and treated for tendinosis (most commonly mis-diagnosed as tendonitis in my right shoulder approximately 5 months ago). Could this issue hinder my right pectoral muscle growth in any way? And if so is there anything I can do to even out the muscular imbalance in my body? I’ve struggled to flex my right pectoral muscle that I only seem to aggravate it at this moment in time. Your time and help is greatly appreciated. I’ve become weary of most sports medicine specialists in the states for a simple consultation on a simple question. I hope to hear of a possible solution from you.