The transversus abdominis, so called for the direction of its fibers, is the innermost of the flat muscles of the abdomen, being placed immediately beneath the internal oblique muscle. The deepest layer of abdominal muscles is called the “transversus abdominis.” The transverse abdominal muscle wraps around the torso from front to back and from the ribs to the pelvis. The muscle fibers of the transversus abdominis run horizontally, similar to a corset or a weight belt.