Here`s a good tip for guys who like preacher curls...................
......example weight being 100 pounds for 6-8 reps.
EXAMPLE:
If you are using 100 pounds for 6-8 reps,drop the weight to 75 pounds,do one rep,followed by one half rep about duh.......halfway up.

This 1 + 1/2 rep will count as one rep.....................
.....controlled movement,stop at the top when you feel the contraction and squeeze,any further up and you lose the contraction.
Slow controlled negative.
Try to get a total of 8 reps counting each 1 +1/2 rep as one rep.
When the set is completed,do 3 more half reps from the bottom position,followed by 3 more half reps from the top position.
This way you won`t cheat,don`t have to go as heavy,and you don`t risk a torn biceps muscle.
Try these 1 + 1/2 reps ......they are fucking murderous trust me.