The abdominal Muscle group consists of four muscles, the rectus abdominus, the external oblique, the inner oblique, and the transverse abdominus. Most people will want bigger muscles, but the abdominal muscles are a little different as most people want definition, not bulk, in the midsection. The muscles of the abdomen help hold in the belly, but they also act to make the waist as small as possible, the transverse abdominus acts as a corset on the waist while the obliques help refine this look by helping sculpt our love handles.
Rectus abdominus: commonly referred to as the six-pack and is often the most focused on portion of the abs. The fibers of the rectus abdominus are superficial and run vertically from the pelvis to the lower part of the chest. The muscle is responsible for bringing the torso towards the trunk and bringing the lower extremities up towards the core.
Effective exercises for developing this area include: Abdominal Crunches, reverse crunches, and jack knife crunches.
External-Oblique: located on both sides of the rectus abdominus and are also located in the superficial layer of the abdomen muscle group. These muscles start at the ribs and attach to the hip, their fibers run diagonally downward and to the front, as if into the front pockets of a pair of pants. The left and right sides can be activated independently to cause lateral flexion, and when combined with the action of the opposite internal oblique we get our cross body (elbow to knee) motion.
Effective exercises for developing this area include: side crunch, Russian twist, elbow to knee (crossbody) crunch.
Internal-oblique: located under the external oblique, their fibers run diagonally downward and to the rear, as if to the back pockets of a pair of pants. Their function is to produce flexion and rotation of the trunk to the same side.
Effective exercises for developing this area include: side to side heel touch, side plank bridges, bicycle kicks.
Transverse Abdominus: located under the obliques and is found in the deepest layer of the abdominal wall. Together with the multifidi muscles of the spine this muscle plays a critical role in providing core stability, specifically these muscles coactivation occurs on average 30 milliseconds before the movement of the shoulders and 110 milliseconds before movement of the legs. This is thought to mean that these muscles feedback is vital to the Central nervous System to stabilize the body during movement.
Effective exercises for developing this area include: Plank, alternating leg plank, side plank.