Many people approach an ab workout looking to target a specific region of their core, without addressing the other areas. This is futile, according to Ben Cohen, a professional strength and conditioning coach who has worked with several championship collegiate teams, including the James Madison University and Louisiana State University football teams. He currently runs Ben Cohen Athletic Advising.

"You don't have lower, middle and upper abs. It's all one muscle," Cohen says. "To effectively target regions of your erectus abdominus, you need to pre-fatigue certain parts of it. With a crunch routine like this one, you'll need to fatigue the top of your abs, then the middle, in order to get to the bottom."

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Working the whole range of your abdominals to a level of fatigue will strengthen both your outer and inner core and improve your overall athletic performance, especially the endurance of your torso muscles.

To accomplish this, Cohen recommends the following ab workout:

Bent Knees Starting Position

• While lying on your back, touch the bottoms of your feet together and pull your heels toward your buttocks.
• In this position, allow the knees to drop out and away from each other, but don't force them.
• With your elbows and hands together in a fist, place both thumbs directly under the chin and keep the upper arms and elbows glued to your chest.

This position forces the abdominals, and ONLY the abdominals, to lift the upper body into the crunch position. The hip flexors, quads, shoulder flexors and arms CANNOT assist the abdominals in this position; the abdominals have to do all the work.

With this isolation, you'll feel a tremendous gain from these crunches in a very short period of time.

More: 3 Advanced Core Exercises for Killer Abs

Upper Ab Workout: Double-Crunch Action

• While keeping your spine stiff as a board, lift the upper body as far as possible and hold for one full second.
• Then, holding that same position without letting the upper body rock back even a fraction of an inch, crunch up with one last thrust. (Blow air out when you do this, much like you hear karate ninjas do in the movies.)

You do it this way because it contracts your inner-core muscles like your multifidus and transverse abdominus, which are your intersegmental stabilizers. If done correctly, the second crunch should be almost unnoticeable but will provide maximum contraction.

Frequency: Without ever resting your head on the floor, repeat five times to start, then progress to a maximum of 15 repetitions over several weeks. You should only progress at a pace that doesn't compromise form.

If you do this exercise correctly, the upper portion of the "six-pack" will fatigue. The middle section is now ready for work.

More: Get Six-Pack Abs With These Plank Exercises

Middle Ab Workout: Offerings Action

The set up for Offerings is the same as for the Double Crunch, except for the arms.

• Position the arms directly to the side of the body, with palms up and backs of hands on the floor.
• Fix your eyes to a point on the ceiling or in the sky directly above and attempt to keep them there throughout the entire exercise.
• Simultaneously lift the upper body with the abdominals and bring the fingers as close as possible to the heels, without actually sitting up. (Your chin should not flex forward toward the chest during any part of this exercise and the backs of the hands should stay in contact with the floor.)
• Once in this contracted position, hold it for two full seconds and then slowly descend to the starting position.

Frequency: Without ever resting your head on the floor, repeat five times to start and work up to a maximum of 15 repetitions over several weeks. You should only progress at a pace that allows the exercise to be done perfectly.
The middle section of your six-pack should be effectively exhausted by now. It's time to fully work the lower abs.
More: Core Workout: 5 Moves for Flat Abs

Long-Leg Double-Crunch Starting Position

• Lying on your back, position your legs together so the hips are allowed to roll outward.
• Point the feet and toes out to the sides with your heels together.

Lower Ab Workout: Long-Leg Double-Crunch Action

Repeat the exact instructions for the Double Crunch in this new position.
Frequency: Without ever resting your head on the floor, repeat five times to start and work up to a maximum of 15 repetitions over several weeks. You should only progress at a pace that doesn't compromise form.
If both the upper and middle part of the six-pack have been previously fatigued through Double Crunch and Offerings, the lower-often neglected-part will also get maximum attention with this ab workout routine.
More: The Best Ab Workouts to Build a Solid Core

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