My traps blew up this week. I've started doing 5 sets of 20-15 reps every other day. I never use to do dumbell shrugs because I never felt that they really worked that well. However,I've been doing them lately and also incorporatng one side at a time shrugs with a moderate weight. I'll usually do my heavy bar shrugs,then dumbell shrugs,then one handed dumbell shrugs with maybe a 65lb. The stretch and contraction are very important. I hold the weight for 3 secs at the top of the contraction and lower the weight as far as I can without straightening my arm all the way or without letting the dumbell slid e down my fingers. I always keep a firm grip and arms slightly bent.