Your abdominal muscles run from under your breastbone all the way to your pubic bone. This set of muscles is called the rectus abdominis. Underneath the rectus muscles are two sets of muscles that run at an angle toward the center of your abdomen, called your obliques. These muscles help you twist and turn and define your waist. The layer beneath the obliques is called the transverses abdominis. Running the entire length of your abdomen, this muscle supports your organs. It also covers a lot of area under your other muscles.

Abs Workout Positions

When exercising your abdominal muscles, it is important to note that the exercises are most effective on these muscles when you do them while lying on your back. During pregnancy lying flat on your back for vigorous exercise is not recommended after about 16 weeks' gestation. Therefore, do your abdominal work in other positions, including all fours, standing, or sitting. You can also alternate a few back-lying (supine) exercises and a few non-supine.