Muscle Group: Forearms
Here we work the forearm flexors in isolation.
Kneel down on the ground, right in front of the middle of a bench. With a pair of dumbbells in hand and palms up, rest your forearms on the bench so that they go across it and also so that the edge of your wrist is at the end of the bench and the dumbbells hang in the air off of it.
Now lower dumbbells all the way down so that you get a stretch in your forearm flexors. Moving nothing but your wrists, curl the dumbbells simultaneously upward until you get a peak contraction in your forearm extensors. Pause for a peak contraction and then lower slowly under control.
Note: For variation, you can also do these in a reverse motion.