Most of the time Its not the trap Its a pinched Nerve In the shoulder than makes it feel like The trap muscle with me thats what It was .. It hurt like hell for a while but went away .. But in the after effects One trap was bigger than the other because On the strain put on the muscle from the nerve .. So this is fixable The trick Is not heavy weight on the smaller side lighter weight on the other .. It's Controled blood flow to the muscle that counts, called Isometrics . LIGHT weight high Reps and a old time trick is when you are at the top of the shrug try squeezing both traps together.. Do this By thinking that a egg is centered evenly bewteen your traps. and at the top of the shrug try squeezing the neck with the traps to squeez the egg like sandwhiching the egg between the traps

Now since we are not 100% this is a muscle strain or a shoulder issue for the first few trap workouts do seated Shrugs with 30# bumpbells keep the back stright and do 4 sets of 50back for sets of 25 front

this will get them back on track, all it is getting the same blood flow back to the muscles