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, you’re probably building your forearms a bit without even realising it. “Any exercise that involves gripping, is going to place demands on the flexors. ~ Berceste