I just flipped through a book called The Body Building Truth, and they hit on this very same subject. Instead of doing Preacher curls, Hammer curls, Reverse Curls, and Easy Curls, you need to lean back. Those other curls focus on the Bi's a little bit but they are mostly hitting the Forearm and the Bracillas Muscle. I have an over active bracillas and I just found out what to do about it. Usually when I hit Bi's my hands or forearms would get tired before my arms, also I noticed that even my Shoulders would get tired. What that book meant by, you need to lean back, they were talking about incline dumbell curls, curls were you lay flat on your back and from a low pulley curl, and also stand in the middle of a cable crossover, grab a cable in each hand from a low pulley take one or two steps forward, put your elbows back and curl up to your nipple and squeese, do not move your elbow. I started doing these curls three weeks ago and my arms are sore as hell the next day. If you are anything like me, your Bi's have never been sore before. I was pretty excited when I woke up the next day with pain in my arms, It's a great feeling, kind of like when you just beat the crap out of your chest and it hurts the next day, but you also feel bigger than life. Yeaaaa it's kinda like that!!!!!