What Muscles are Worked in the Best Ab Workout?

The best ab workout is one that hits all of the muscles (pictured below) in the abdominal region. These muscles include:
Obliques (Internal and External). Your obliques are located on the side and front of your midsection, right around your waist. The internal obliques are located just below your external obliques. As you can see in the picture, the internal obliques cross the external obliques diagonally. The obliques are responsible for twisting movements and bending at the side.

Best six pack ab workout exercises (links open in new window): Oblique Crunch, Russian Twist
Rectus Abdominis. For most people, this muscle is the one that they are thinking of when they say they want six pack abs. This pair of muscles runs along the front of the abdomen and is separated vertically by the linea alba. It is crossed by 3 or 4 fibrous bands called the tendinous inscriptions. These bands are what produces the six pack when the abdominal region is well defined.

Best six pack ab workout exercises: Standard Crunch on Exercise Ball, Hanging Leg Raises, Cable Crunch

Transverse Abdominis. The Transverse abdominis is the depest muscle in the abdominal region and is located just under the internal oblique muscle. Though you cannot seen the tranverse abdominis, it acts as a "corset" to help hold your stomach flat and aid with pelvic stability. Not only will this muscle help with definition for your six pack abs, but it will also help you to use more weight in all of your lifts, due to its "weight belt" effect.

Best six pack ab workout exercise: Vacuum



These three groups of muscles make up your six pack abs. However, there is one other group of muscles that should not be ignored to round out your core muscles.

Erector Spinae. The Erector Spinae is a collection of three muscles running from your neck to your lower back. The are called the splenius, logissimus, and the Iliocostalis. These muscles act to extend your back and are important for overall posture. Working these muscles balances the work you are doing with your abdominal muscles and should be worked when performing this ab workout.
Best six pack ab workout exercise: Back Extensions on Exercise Ball

You will notice that I prefer to use the the exercise ball for many of the exercises in the best ab workout. The exercise ball (sometimes call a Swiss ball) allows for a greater range of motion. If you were to simply lie on the bench or floor for crunches, you are not working the abdominal muscles through their full range of motion.

However, if you do not have an exercise ball, you should not hesitate to perform these exercise without it; you will still get an outstanding workout.