A: There are four parts to the abdominal wall. The six-pack muscle is the rectus abdominis, commonly called the abs. It’s the front muscle of the abdominal wall, connecting the pelvis to the lower ribs. It compresses the abdomen and flexes the trunk. Some people don’t have a six-pack but more of a four-pack, and a few have more of an eight-pack. Even if your abs aren’t visible, you can feel your particular formation if you push through the subcutaneous fat into tensed abs and sense how many clear rows of muscle you have there.
The obliques are the two muscles at each side of the abdominal wall—the external abdominal obliques and internal abdominal obliques—connecting the ribs with the pelvis. They compress the abdomen and flex and rotate the trunk.
The transversus abdominis is the deep muscle of the abdominal wall, beneath the rectus abdominis and the obliques. It compresses the abdomen and flexes the trunk.
The quadratus lumborum is the deep muscle on either side of the lower spine that helps form the rear of the abdominal wall.
Editor’s note: Stuart McRobert’s first byline in IRON MAN appeared in 1981. He’s the author of the new BRAWN series, Book 1: How to Build Up to 50 Pounds of Muscle the Natural Way, available from Home Gym Warehouse (800) 447-0008 or www.Home-Gym.com.