Would this site help?
Bodyteen Muscular Anatomy Arms (Scroll down to "wrist curls")
Hello can someone explain those sentences that highlight in green, red and blue colour, please? I dont understand what it mean.
"This keeps a stronger biceps from overshadowing the weaker, which can result in asymmetrical arm development. Also, be sure to twist the wrist during the movement for total biceps contraction.
"However, I believe one major reasons bodybuilders show weak points in the biceps is that they do the exercises incorrectly. You need to master proper technique--keeping the elbows steady, lowering the weight rather than dropping it, employing as many Shocking Principles as possible--and then you will be much less likely to have problems in this area.
"For example, I see a lot of bodybuilders using their forearms when they do curls, starting the motion with a kind of Wrist Curl which takes away from the effectiveness of the exercise.
"Or they will do a Curl and, at the top, instead of flexing their biceps--to maintain maximal tension--they will just throw the weight back toward their shoulders, leaving the biceps loose and not working at all. I recommend instead using the peak contraction principle--flexing the biceps as hard as possible when you get to the top of the Curl."
Thank... How how have you been training?