Place your forearms on the floor with elbows aligned under your shoulders and arms parallel to your body at about shoulder width, if flat palms bother your wrists, clasp your hand together.
A forearm plank should be low, but parallel to the ground. If your bottom is in the air or your core forms an inverted V, your doing it improperly. Disperse your weight evenly between your forearms and toes. The plank is to strengthen your core muscles, particularly those in your abdomen and back. Its mainly targets the erector spinae, rectus abdominis and transversus abdominis. It also works muscles in your shoulders, chest, buttocks and legs.