The forearms are made up of a bunch of smaller muscles that move in four main ways: wrist flexion (bending your palm inward) wrist extension (raising the back of your hand) forearm pro-nation (rotating the palm down) and forearm supination (rotating the palm up). Keep in mind though youre probably building your forearms a bit without even realising it. Any exercise that involves gripping is going to place demands on the flexors. The forearms are made up of a bunch of smaller muscles that move i