sure.
warming up doesnt neccesarily mean pyramiding up to your working sets.
Take a MONSTROUS 2.5lber and make big ass circles with your shoulders. Do some rotator-cuff movements. Get those arms swingin'. Take a light bb and mimic shoulder pressing, upright and bent rowing, curling etc.
That's what i do. Not only does it warm you up, but i get a nice pump going which fires me up, plus it gives me a chance to put my mind in my muscle, so i'm flexing the right muscles when i train.
give it a shot, bro...