PREPARATION
1.Take a dumbbell in your left
  hand and raise it to your
  shoulder.

2.Sit astride the bench and rest
  your upper-arm and elbow on
  the pad.

EXERCISE
1.Keeping your wrist straight,
  breathe in as you lower the
  dumbbell under control. Stop
  while your arm is still slightly
  bent. 

2.Keeping your upper arm pressed
  against the pad, breathe out as
  you raise the dumbbell back to
  the start position.

Do not twist your upper arm to
help raise the weight: allow your
bicep to do all the work.

MAINLY FOR: Bicep