The abdominal muscles are located between the ribs and the pelvis on the front of the body.  They support the trunk, allow movement, and hold organs in place by regulating abdominal pressure. That’s certainly a lot of work for one muscle group, so just like any other huge job, tasks are delegated. The abdominal muscles are made up of four different muscle groups, all with their own assignments. Those four groups are the transversus abdominis, the rectus abdominis, the external oblique, and the internal oblique; 

Transversus abdominus - the deepest abdominal layer and the most highly overlooked muscle group of them all.  This group has the prestigious job of stabilizing the trunk and maintain internal abdominal pressure.   The best way to work the transversus is with stability exercises.  (For example: Planks,  in which you hold a push-up-like position on your elbows) are a very good exercise for this muscle group.

Rectus Abdominus - found between the ribs and the pubic bone at the front of the pelvis, it is attached to the transversus muscle and is the muscle group famous for its ability to be moulded into that sliced and diced six-pack everyone idolizes. But, besides drawing admiring stares and envious glares, the rectus abdominis controls the tilt of the pelvis and curvature of the lower spine. In other words, it allows you to bend forward and from side to side.  A lot of the more well-known exercises work this area of the abs because of its aesthetic popularity, but one of the more effective ones is the V-sit. This is where you start in a prone position on your back with your arms stretched out above your head. You then bend your body at the hips, bringing your hands to meet your feet in the air, and then end back in the prone position. It’s a tough one, but it sure gives you hardcore results.   

External Obliques - these are on each side of the rectus abdominus.  The External oblique muscles allow the trunk to twist (to the opposite side of whichever external oblique is contracting)  - For example: the right external oblique contracts to turn the body to the left. (Daily living: using a shovel to dig)

Internal Obliques - these flank the rectus abdominus and are located just inside the hip bones.  They operate in the opposite way to the external oblique. (For example: twisting the trunk to the left requires the left side internal oblique and the right side external oblique to contract together).  (Daily living: using a rake)

THINGS TO REMEMBER:

• The abdominal muscles support the trunk, allow movement and hold organs in place by regulating internal abdominal pressure.
• The abdominal muscles support the lower back so,  people with weak abdominal muscles tend to suffer from back pain
• Causes of abdominal muscle strains include overstretching, overuse or a violent,  poorly performed movement of the trunk