Planks are a very important part of any exercise routine. This move specifically activates and works the transverse abdominis, the deep ab muscle that wraps around your stomach like a belt and holds everything in. Planks are one of the few ab exercises that actually activates this deep muscle, but it is essential to work in order to have a strong core. Make sure your workout routine includes at least one type of plank, and work to strengthen and improve your planks over time.