My goal is to improve the flexibility in arms: I want to get symmetric flexibility to the right and left. I am right-handed in writing but left-handed in most club games. The right side is becoming too strong and less flexible. I am trying to find ways to address the issue, I noticed the issue when I was doing warmup before some bench presses.
I am not sure which muscles are not relaxed: perhaps supraspinatus, infraspinatus and teres minor. After doing more and more trials, I can feel more stretch in the right joint -- perhaps I haven't just warmed up enough?
How would you improve the flexibility so that I could one day be able to do the movement touching both hands in both sides?