The reverse plank is an exercise that is often forgotten, and it is great for the core muscles. It targets the posterior muscles (those along the back of the body), but, if done correctly, it also involves the abdominal muscles. Although this exercise is most often found in yoga classes, it is a good addition to any basic workout. Beginners should start by studying the usual bar. Continue to hold the reverse bar for just a few seconds at a time, maintaining the correct shape.