I have been resuming exercising in GYM, after a long time (approx 3 years). I started with mix light weight exercise including, Biceps, Triceps, Chest, Shoulder+Back. Now after two weeks (10 days, Saturday and Sunday rest), I was feeling strong and I have started, separate work routine for separate body part. Monday Biceps, Tuesday-Triceps, Wednesday-Chest and Thursday-Shoulder Back.Its been two weeks, I have been repeating this schedule. I set weights so that I can do 3 sets, and each set should have these many reps 12-10-8 (I will increase eventually after month or two).
Today, when I was doing shoulder press, I have felt pain in my left shoulder blade (as per my experience it will go but will take so much time). Pain comes only when I am lifting the rod up.But when I simply leave rod on shoulder or coming down from top, pain is very minute. Also when I don't have weights (I am relaxing ), I squeezing my back or say contracting/joining both blades together I don't feel any pain.
I don't understand whats the reason of this pain and how to get rid of this?