In my experience, biceps grow best when they're trained in an accessory fashion. That is, heavy back work provides the heavy bulk of work for the biceps and a few sets of isolation work after heavy back training is enough. If you're training your pulls, rows and pull-ups heavily then 2-3 sets, two or three times a week of direct biceps work is not only enough, it's ideal. And the harder your biceps cramp during the direct work the better. I always got my best biceps growth, by far, from dumbbells. | 
