Thought I would share the following exercise with you guys and see what you think...
On a day that I'm working biceps, I do the following exercise last:
1) Put a stirrup handle on a low pulley
2) Begin with a supinated grip, as if doing isolation curls
3) Come up 50% of the way (forearm parallel to the floor)
4) Pause for 1 sec
5) Go down to having your arm bent 25% of the way (as if returning to full extension, but stopping before tension is lost)
6) Perform a normal concentration curl
7) This is one rep; repeat steps 3-6 for reps
I've never seen this described as an exercise anywhere. I began doing it because I remembered hearing it said that the lower 50% of the curl is usually the most difficult, so I thought I'd do the more difficult part twice. I get a crazy pump from this exercise; it usually feels like I have a baseball inserted under my skin instead of a bicep when I'm finished.