STEP 1. Using an underhand grip, take hold of the barbell with your hands a few inches apart. Sit on the end of a bench, keep your back flat while resting your forearms on it but making sure that your wrist and hand hang off the end.
STEP 2. Allow your wrists to bend back and the barbell to roll to the ends of your fingers. Close your fingertips as you curl your palms toward your biceps.
STEP 3. Pause, reverse the motion, and let the bar roll back to your fingertips.