Plank

The Mother of All Core exercises! This is a foundational exercise, although you won't be moving at all. This is an isometric hold. This can be performed either on your forearms, or on your hands. You are pressing into the ground and holding your body straight as a board (hence the term "plank").

Make sure your hips are down in line with the rest of the body and not in an upside down "V". Look at your reflection to correct your form if needed.