This is the first upper body functional anatomy post of the Anatomy For Athletes Mini-Series.  Check out parts 1 through 5 to learn the key functions, training considerations, and exercises for the glutes, hamstrings, quadsadductors, and calves.

Functional Anatomy of the Abdominal Muscles

The abdominal wall consists of four muscles – rectus abdominis, external obliques, internal obliques, and transverse abdominis.

When we think of functional anatomy, we tend to focus on how muscles produce motion.  However, the abdominal muscles serve the dual function of both producing motion and preventing it, as they stabilize the pelvis and lower back.  Be sure to keep this dual function in mind when designing your training programs.

The specific functions of each abdominal muscle is outlined in the paragraphs that follow…

How To Design Your Own Training Programs

Rectus Abdominis

The rectus abdominus is the most superficial abdominal muscle.  It extends from the pubic bone to the rib cage and sternum.

The primary function of the rectus abdominus is trunk flexion.  However, its lower fibres contribute to hip flexion as well.

Examples of Rectus Abdominis Exercises

  • Sit-up variations
  • Crunch variations
  • Reverse crunches
  • Leg lift variations
  • Dead bug
  • Plank variations

Internal and External Obliques

The internal and external obliques rely on each other to produce movement, so we’ll examine them together.

The internal and external obliques are deep and lateral to the rectus abdominis, with the internal oblique sitting deep to the external oblique.  They produce various movements depending on which portions are recruited.

When both the left and right sides contract equally, they assist the rectus abdominis with trunk flexion while also aiding in compression of the abdominal wall and increasing intra-abdominal pressure.

When each side acts individually, the obliques aid the spinal erectors and quadratus lumborum in producing trunk rotation and lateral flexion (side bending).

When producing rotational movements, the internal oblique on the side you’re twisting to contracts with the external oblique of the side you’re twisting from.

When contributing to lateral flexion, the same-side internal and external oblique work together to produce the movement.

Examples of Internal and External Oblique Exercises

  • Full contact twists
  • Russian twist variations
  • Woodchop variations
  • Side plank variations
  • Windmills and Bent Presses
  • Saxon Side Bends

Transverse Abdominis

The transverse abdominis is the deepest muscle of the abdominal wall.  Its primary function is to compress the abdominal contents, stabilize the pelvis and lower back, and aid in production of intra-abdominal pressure.

Examples of Transverse Abdominis Exercises

  • Plank variations
  • Vacuums
  • Abdominal bracing exercises performed in the quadruped position (e.g bird-dogs)
  • Dead bug
  • Any movement that requires you to brace your stabilize your spine against a load (squats, deadlifts, overhead presses, etc.)

Considerations For Training

It’s important to train the abs because a strong core is critical for stabilizing the body during heavy lifts, activities of daily living, and sport specific movements.

From my experience, most people don’t train their abdominal muscles properly.  If I walked into a commercial gym and asked a hundred people what exercises are best for their abs, most of them would probably answer crunches and sit-ups.  But…sit-ups and crunches only train spinal flexion and can also cause other problems, like:

  • Too much compressive force on the back.
  • Increased risk of back pain and/or injury.
  • Shortening of the rectus abdominis muscle resulting in a kyphotic or slouched upper body posture.  (Think Quasimodo).

So…  Step number 1 for improving your abdominal training program is to ditch the sit-ups and crunches.  Instead, include exercises for all of the basic abdominal functions:  flexion, rotation, lateral flexion and stabilization (more on the types of stabilization exercises below).

There are a number of different ways to implement this, but a simple method is to train or or two of these movement functions during any given workout.  For example, if you workout four days a week, use flexion-based exercises one day, rotational exercises another, and so on.

Let’s discuss each function in greater detail…

Flexion Exercises

Before I get into discussing flexion-based abdominal exercises, I need to point out one important thing.  There’s no such thing as “upper” and “lower” abdominal muscles.

The upper and lower portions of the rectus abdominis muscle have a common serve supply, so they can’t be isolated into upper and lower sections.  However, for ease of explanation, when I refer to “upper-fibre dominant” exercises in this section, I’m referring to trunk flexion.  And when I refer to “lower-fibre dominant” exercises, I’m talking about pelvic stabililization, pelvic tilt, and anti-extension exercises.

Upper Fibre Dominant Exercises:

  • Curl-up (see video above) and sit-up variations
  • Crunch variations
  • Ab wheel or barbell rollouts

Lower Fibre Dominant Exercises:

  • Reverse crunches (see video above)
  • Dead bug (see video above)
  • Leg lift and leg lowering variations
  • Jackknife variations
  • Pelvic tilts

Most people tend to have an anteriorly tilted pelvis (i.e. an excessive lower back curve), so be sure to include lower fibre dominant exercises because they promote stabilization and posterior pelvic tilt.

Exercises like reverse crunches, dead bugs, and leg lift variations are far more advantageous than crunches and sit-ups because they help maintain a neutral pelvic alignment.  This in turn reduces pressure and pain in the lower back.  It also improves strength and performance.

Rotation Exercises

Rotational exercises should be included because many sport-specific and everyday movements involve twisting with a load.  Rotation-based exercises also promote thoracic spine mobility (as long as the pelvis is stabilized throughout the movement).

The prime movers during rotation-based exercises are the external obliques, but the internal obliques and rectus abdominis also help produce torque and coordinate the movement.

Examples of rotation-based abdominal exercises include:

  • Full contact twist (see video above)
  • Woodchop variations
  • Medicine ball chop variations

Lateral Flexion Exercises

Lateral flexion exercises are often neglected.  More often than not, when I see people doing lateral flexion exercises they generally perform plate or dumbbell side bends.  An okay exercise, but there are others that I think are far better.

(Oh, and a tip for those of you that include side bends in your program… It doesn’t really work if you hold weight in both hands.  Picture a see saw with the same amount of weight on each side, it wouldn’t move, right?… So if you’re going to do side bends, only hold weight in one hand.)

Or, try these exercises instead, because they’re better…

  • Windmills (see video above)
  • Bent presses
  • Saxon side bends

Stabilization Exercises

Core stability is the ability to maintain a neutral torso and pelvic alignment while resisting motion imposed by the extremities.  It is important because a lack of stability can result in injury and/or poor performance.  (Lack of mobility will also result in these issues, but we’ll discuss that some other time…)

If you include core stability exercises in your program you will improve muscle recruitment, muscle activation, posture, and tone.  You’ll also reduce your risk of pain and injury.

Core stabilization exercises fall into four categories — anti-extension, anti-rotation, anti-lateral flexion, and hip flexion while maintaining a posterior pelvic tilt.

Anti-Extension Exercises

The goal of anti-extension exercises is to resist lumbar extension (arching of the lower back) by bracing the abs and glutes to produce hip extension.  In other words, the goal is to maintain a neutral pelvic and lower back alignment.  Examples of anti-extension exercises include:

  • Plank variations
  • Jackknife variations
  • Rollout variations

Anti-Rotation Exercises

When performing anti-rotation exercises, the goal is to resist rotation around your lumbar spine (lower back) by bracing your abs and glutes to stabilize your pelvis.  Examples of anti-rotation exercises include:

  • Pallof press variations
  • Landmine anti-rotations

Anti-Lateral Flexion Exercises

Anti-lateral flexion exercises involve resisting a side-bending motion.  Examples of lateral-flexion exercises include:

  • Side plank variations
  • Suitcase deadlift variations
  • Single-arm farmer's walk
  • Waiter's walk

Hip Flexion While Maintaining A Posterior Pelvic Tilt

Lots of people find it difficult to produce hip flexion while maintaining a posterior pelvic tilt.  These people often have tight hip flexors and inhibited abdominal muscles, so their pelvises tend to tilt anteriorly (causing an excessive curve of the lower back).

These types of exercises are often avoided because of the difficulty involved in performing them with proper technique.  But they’re essential because they help to maintain a neutral lower back and pelvic alignment, which is important for sport performance, activities of daily living, and strength training.

Examples of exercises that train hip flexion in a posterior pelvic tilt include:

  • Leg lowering variations
  • Dead bugs (see video above)
  • Reverse crunches (see video above)
  • Bird-dogs
  • Jackknife variations

If you find it difficult to stabilize your back and maintain a pelvic tilt when performing these types of exercises, be sure to start with basic progressions and work up from there.  You might even need to start with just partial range of motion.

Final Discussion Points...

There you have it folks… a somewhat short summary of how the abdmominal muscles function and what you should take into consideration when designing your training programs.

But before I wrap things up…  I’d like to leave you with a couple more things to think about…

I find that lots of people tend to use very high rep training for their abs.  Are you one of these people?  Keep in mind that the abs are just like any other muscle group — in order to improve strength and size, you have to load them.  Use the overload and variability principles just like you would for any other muscle group.

And, finally…

I’d like to introduce an exercise that incorporates all of the primary abdominal functions that I discussed in this article:  The Turkish Getup.

This is an excellent exercise to include because it has a number of other benefits beyond increasing core strength and stability.  It also improves hip mobility, hip extension, thoracic extension, and shoulder stability.  It’s also fun to do and teach.

Enjoy shredding those abs. Check back soon for the rest of the Anatomy for Athletes Mini-Series.

Bye for now.

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How To Design Your Own Training Programs

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