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Abdominal Muscle Anatomy
Abdominal Muscle Anatomy can be very complex, but let's just keep it simple here. The Abdominal Cavity is the region between the pelvis and the thorax. The diaphragm forms the top of the cavity and separates the abdominal cavity from the thorax and the pelvic floor muscles are the bottom of the abdominal cavity. There are 4 abdominal muscles that are in the posterior abdominal wall, and there are 4 abdominal muscles in the anterior abdominal wall. The anterior abdominal wall is what most people imagine when they think about abdominal muscle anatomy. Anterior Abdominal Wall Muscles The anterior abdominal wall consists of 4 muscles: the rectus abdominus, the external obliques, the internal obliques, and the transversus abdominus. The Rectus Abdominus is the muscle that is considered the 6 pack. Rectus means "straight" and abdominus refers to "the abdomen". This muscle goes straight down the abdomen. It attaches to the ribs and the pelvis and pulls your body forward like in a crunch. It has little tendinous intersections that act to add leverage and give this muscle the 6 pack abs appearance. In regards to stability, it works with the other core muscles to keep the spine and pelvis stable. The External Obliques are just under the skin on your sides. They start on the back of the lower ribs and run on a diagonal down towards the pelvis. They pull the spine forward just like the rectus abdominus, but because they are oriented on an angle they also help to rotate and twist the spine. In addition, the external obliques help to bend the waist and spine to the sides. Your external obliques work the hardest when you twist or side bend. If you are really lean you should be able to see the rectus abdominus and the external oblique because these muscles are just underneath the skin. The next two abdominal muscles are underneath the first two so you cannot see them unless you do dissection. The Internal Obliques are underneath the external obliques. They start on the pelvis and run up towards the ribs in a diagonal line. They help to pull the spine forward like in a crunch, and they also help to twist and side bend the spine. Since they are deeper and closer to the spine than the external obliques, they play a slightly larger role in stabilizing the pelvis and spine. Here are some oblique exercises The Transversus Abdomnius is the deepest of the 4 anterior abdominal wall muscles, and it plays the greatest role in stabilizing the lower back. In fact it does not bend the spine forward like in a crunch, and it does not twist or side bend the spine. Its only job is to stabilize the lower back! Physiologist have also determined that the transversus abdominus is the first muscle that is activated during movements. In healthy people it contracts to stabilize the lower back before the arms and legs move. This is an important function, and people who suffer from lower back pain usually have delayed responses in the transversus abdominus, which means their spine is less stable. Physical Therapists use the Drawing-In Maneuver to re-train the transversus abominus. You cannot see the transversus abdominus if you look at someone because it is underneath the obliques. Here is a picture of all 4 anterior abdominal muscles.
This is a brief overview of the abdominal muscle anatomy and 6 pack abs, and I hope it helps you to understand the orientation of the abdominal muscles. Yours in Health,
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