in case you guys didn't know, the trapezius extends far down the back. Only doing shrugs will put the emphasis primarily on the upper traps, which is good. But your trapezius almost functions as three muscles (upper, middle, and lower). The best way to target the whole thing is to do upright rows. And the reason why your wrists hurt is because when your humerous (upper arm) comes above parallel to the floor (bar to the chin) with your wrists too close. ulnar flexion occurs. Bad for wrist! anyway i found that doing them correctly and with shoulders shrugged through the entire ROM is very effective without momentum of course.