The Inner Unit

How many ways can you do a crunch? Well, if you have been reading the muscle tabloids for the past 20 years you could probably come up with well over 100. Today we have classes devoted to nothing but TRASHING people’s abdominals, complete with every variation of crunch, jack knife, side bend and leg raise known to man. Are these classes, or these exercises, really improving the way you look or function, or reducing your chances of back pain?

To find the answers to these questions, in 1992 I began investigating correlation’s between abdominal exercises performed, exercise volume and the postural alignment, pain complaints and overall appearance of my clients. To ensure objective observations of postural alignment and responses to specific exercises, I designed and patented calibrated instruments to measure structural misalignment.

In the first year of recording such information as forward head posture, rib cage posture, pelvic tilt and overall postural alignment, it became evident that those performing high volume sit-up/crunch exercise programs were not showing promising results (see Figure 1)! Not only were those attending "Ab Blast" classes and/or performing high repetition/high volume abdominal routines having a harder time recovering from back pain, they were also having slower or nonexistent improvement in their postural alignment.

FIGURE 1. Poor Posture and Abdominal Training

Those regularly performing crunch and sit-up type exercises frequently demonstrate forward head posture (A); note that when head carriage is normal the dotted line through the cheekbone should fall in the same vertical plane as the sternum and pubic symphysis. (B) As the rectus abdominus becomes chronically shortened, it pulls the chest downward, increasing first rib angle; this is commonly associated with shoulder dysfunction and impingement of the nerves feeding the arm as they exit the cervical spine. (C) As the hip flexors strengthen and shorten from chronic exposure to the sit-ups, leg extension and leg lowering exercises commonly used in abdominal workouts the lower abdominal and hamstring muscles are lengthened, frequently demonstrating positional weakness. The postural changes demonstrated here are common among today’s athletes and can be corrected through improved control and strengthening of the inner unit musculature.

While studying patients and clients who performed high volume abdominal routines, it became very evident that there was a common link. About 98% of those with back pain had weak lower abdominal and transversus abdominis muscles, while those with no current or history of back pain were frequently able to activate the transversus abdominis and scored better on lower abdominal strength and coordination tests. Frequently, to alleviate back pain, I had to suggest that clients stay completely away from any form of sit-up or crunch type exercises. When this advice was adhered to, and exercises for the lower abdominal and transversus abdominis practiced regularly, back pain decreased or was completely alleviated and posture routinely improved.

All the while, some "experts" in the health and fitness industries could be found stating that, "There is no such thing as lower abdominal muscles," while others suggested that the best treatment for back pain was to exercise on machines that isolated the low back muscles. My clinical observations led me to believe both theories were wrong.

In 1987, "Clinical Anatomy of the Lumbar Spine" by Nikolai Bogduk and Lance Twomey was published (1). This book is important in this story because it was Bogduk who made the first real clinical observations concerning how the abdominal and back muscles work together as a functional unit. This occurs via the connection of the transversus abdominis and internal oblique to the envelope of connective tissue (thoraco-lumbar fascia) surrounding the back muscles (Figure 2). Only a few years later, Australian researchers Richardson, Jull, Hodges and Hides began making significant headway into the understanding of how the deep abdominal wall works in concert with other muscles, creating what they would later call THE INNER UNIT (2).

FIGURE 2. Thracolumbar Fascia and Inner Unit

The thoracolumbar fascia system envelops the inner unit musculature to create the body’s own natural weight belt. Activation of the transversus abdominis aids in stabilization of the lumbar spine. When wearing a weight belt, the natural tendency is to push outward against the belt, which inhibits the transversus abdominis and may lead to faulty motor programming and destabilization of the spine! ©Paul Chek Seminars 1999

THE INNER UNIT

The Inner Unit became a term describing the functional synergy between the transversus abdominis and posterior fibers of the obliquus internus abdominis, pelvic floor muscles, multifidus and lumbar portions of the longisssimus and iliocostalis, as well as the diaphragm (Figure 3). Research showed that the inner unit was under separate neurological control from the other muscles of the core (2, pg. 49). This explained why exercises targeting muscles such as the rectus abdominis, obliquus externus abdominis and psoas, the same muscles exercised with traditional abdominal conditioning programs used in gyms and athletic programs worldwide, were very ineffective at stabilizing the spine and reducing chronic back pain.

FIGURE 3. THE INNER UNIT

The inner unit is under separate neurological control from the larger outer rectus abdominis, external obliquue and anterior fibers of the obliquus internus. Traditional gym exercises do not condition these key muscles such that their ability to improve spinal stability is enhanced until their recruitment is under automatic reflex control. To accomplish automatic reflex control of the inner unit requires specific isolation training to enhance sensory-motor control. Once control is established, activation of the inner unit must be programmed into all movement patterns commonly used by the host. Failure to condition the inner unit to a high level of specificity often results in spinal injury due to instability.

Exercising the big muscles (prime movers), was not providing the correct strengthening for essential small muscles, such as the multifidus, transversus abdominis and pelvic floor. When working properly, these muscles provide the necessary increases in joint stiffness and stability to the spine, pelvis and rib cage to provide a stable platform for the big muscles. In a sense, as the big muscles (outer unit) became stronger and tighter the delicate balance between the inner and outer units becomes disrupted. This concept is easier to understand using the pirate ship model (Figure 4).

FIGURE 4. A PIRATES VIEW OF THE INNER AND OUTER UNITS

Although the large guy wires (outer unit) support the mast of the pirate ship, its functionality is completely dependant upon the support provided by the small guy wires which are representing the multifidus and inner unit muscles in this analogy.

The mast of the pirate ship is made of vertebra which are held together (stiffened) by the small guy wires running from vertebra to vertebra, just like the multifidus (a member of the inner unit) do in the human spinal column. Although the big guy wires (representing the outer unit) are essential to holding up the mast of the pirate ship (our spine), they could never perform this function effectively should the small segmental stabilizers (inner unit) fail. By viewing the pirate ship’s large guy wires, it becomes easy to see how developing too much tension from the over-use of exercises such as the crunch, could disrupt the posture of the mast, or spinal column in the case of a human.

To better apply the concept of the pirate ship, let’s examine how the inner and outer units work in a common situation such as picking dumbbells up from the floor in the gym (Figure 5). Almost in synchrony with the thought, "Pick up the weights from the floor," the brain activates the inner unit, contracting the multifidus and drawing in the transversus abdominis. This tightens the thoraco-lumbar fascia in a weight belt-like fashion (Figure 2). As this is happening there is simultaneous activation of the diaphragm above and the pelvic floor below. This works to encapsulate the internal organs as they are compressed by the transversus abdominis. This process creates both stiffness of the trunk and stabilizes the joints of the pelvis, spine and rib cage, allowing effective force transfer from the leg musculature, trunk and large prime movers of the back and arms to the dumbbells.

FIGURE 5. FUNCTIONAL USE OF THE INNER AND OUTER UNITS

Such functional tasks as picking up dumbbells off the gym floor require synergistic function of the inner and outer units. Failure of the inner unit for any reason, predisposes the spine to forces that frequently can not be effectively stabilized and dissipated, resulting in spinal injury and/or sacroiliac joint injury.

When the inner unit is functioning correctly, joint injury is infrequent, even under extreme loads such as pushing a car, tackling an opponent in football or lifting large weights in the gym. When it is not functioning correctly, activation of large prime movers will be no different than a large wind hitting the sail of the pirate ship in the presence of loose guy wires running from vertebra to vertebra in the mast. Any system is only as strong as its weakest link!

INNER UNIT CONDITIONING TIPS

The first, and most important step, toward reducing back pain and/or improving posture, which in turn generally improves aesthetics, is to stop all crunch and/or sit-up type exercises until you become proficient at activating your inner unit! Although the assessment procedures for the inner unit are beyond the scope of this article, the interested reader may find detailed information in the video series Scientific Core Conditioning (3). Because inner unit dysfunction is extremely common in today’s working and exercising population, it is safe to assume that everyone needs to start with beginning exercises, even the most elite of athletes.

To begin conditioning the transversus abdominis, use the 4 Point Transversus Abdominis Trainer (4) (Figure 6). For conditioning of the multifidus and related stabilizer and postural muscles the Horse Stance exercises may be used (4,5,) (Figures 7-9). Although the exercises may seem simple from looking at the diagrams here, they are actually very technical and must be executed with exquisite precision (see Scientific Back Training (5) or The Golf Biomechanic’s Manual (4) for more details). These exercises are only a small sample of the number of inner unit exercises available (4,5), but, when done correctly, they are sufficient to make a noticeable difference in the way your body functions.

To get the most from the inner unit exercises shown here it is suggested that the exercises be done 3-4 times per week as an individual workout. To get best results from these exercises while continuing with a traditional gym program, I suggest you stop all crunch and sit-up exercises and replace them with the exercises demonstrated here. Always perform an inner unit exercise as the last exercise of your training session, i.e. perform one exercise after each workout. Alternate through the exercises, selecting either the 4 Point Transversus Abdominis Trainer or a variation of the Horse Stance exercises after each training session. It is very important not to fatigue the stabilizer system before attempting traditional free weight exercises or injury is likely!

If you are implementing the stabilizer exercises into a machine-based program then you may intersperse the exercise among the machine exercises. Because of the inherent stability provided by machines, it is unlikely that you will become injured. As your stabilizer system improves, I suggest progressively replacing machine exercises with free weight exercises, as machine-based programs do nothing to enhance functional strength and stability. Should you begin adding free weight exercises to a machine-based program, you must always perform your stabilizer training after completion of all free weight exercises.

FIGURE 6. 4 POINT TRANSVERSUS ABDOMINIS TRAINER

• Assume the start position as shown in Figure 6.
• With the spine in neutral alignment, take a deep breath in and allow your belly to drop toward the floor.
• Exhale and draw your navel in toward your spine as far as you can. Once the air is completely expelled, hold the navel toward your spine for ten seconds, or as long as you comfortably can without taking a breath (not longer than ten seconds). Throughout the breathing pattern, keep your spine motionless.
• This process should be repeated ten times to complete a set.
• Rest one minute after completing one set. As you are able, build up to completing three sets of the exercise.

FIGURE 7. HORSE STANCE VERTICAL

• Place your wrists directly below the shoulders and your knees directly below their respective hip joint.
• The legs are parallel and the elbows should remain turned back toward the thighs with the fingers directed forward.
• Place a dowel rod along your spine and hold perfect spinal alignment. The rod should be parallel to the floor. The space between your lower back and the rod should be about the thickness of your hand.
• Draw the navel inward toward the spine just enough to create a space between your belt and your stomach.
• It is advisable to find a spotter who can assist you with feedback about your body position. If you are not training with a spotter, it is highly recommended that you train in front of a mirror to make sure you stay in correct position throughout the exercise. When you are checking your body position in the mirror, do not move your head, just look up with your eyes.
• The Horse Stance Vertical is initiated by lifting one hand off the floor just enough to slide a sheet of paper between the hand and the floor or mat. The opposite knee is then elevated off the floor to the same height. Keep the dowel rod level at all times. Hold this position for ten seconds. After ten seconds, alternate hands and knees, again lifting them only enough to slide a sheet of paper between the extremity and the mat.
• The target number of repetitions is ten reps per side with a ten second hold in each position. When you are able to complete the exercise for three sets with a one minute rest between sets, you are ready to add the Horse Stance Horizontal to your program. Perform one set of the Horse Stance Vertical as a warm-up for the Horse Stance Horizontal.

FIGURE 8. HORSE STANCE HORIZONTAL

• The start position is identical for all Horse Stance exercises.
• Raise one arm to a point 45° off the midline of the body and hold it in the same horizontal plane as the back. (See Figures 8A and 8B). Always keep the thumbs pointed upward to increase lower trapezius activation.
• Elevate the leg opposite the arm you have raised (left arm / right leg and vice versa) to the point at which your leg is in the same horizontal plane as your torso. As you elevate the leg, do not tilt your pelvis forward; you will know if this happens if the space between the stick and your lower back increases. Hold the leg out straight, activating the muscles of the buttocks.
• At no point during the exercise should your shoulder girdle or pelvis lose their horizontal relationship with the floor. It is quite common for the shoulder to drop on the elevated arm side and for the hip to raise on the side of the extended leg. Either of these faults constitutes poor form!
• The arm and opposite leg are now held in this position for ten seconds before switching sides. Repeat ten times per side, providing you can maintain perfect form. Again, watch yourself in the mirror intermittently or have a spotter check your form. It is critical that you only perform as many repetitions as possible with perfect form! Failure to follow these instructions will result in futile attempts at conditioning and no improvement. Lack of attention to detail is exactly why many exercise programs fail!

FIGURE 9. HORSE STANCE ALPHABET

• From the same start position described for the Horse Stance Horizontal (Figure 8A), place the dowel rod along the spine as seen in Figure 9.

• With the arm 45° to the side and the thumb up, use the extended leg to draw letters of the alphabet. Start with small letters of 4-6 inches high and progress to larger letters as you are able to stabilize your core and keep the dowel rod in place.

• When performing the exercise, it is important to make sure the following checkpoints are met:

• The head and neck should stay in line with the spine. The head should not drop down nor look up at any time.
• Elbow of support arm should point directly backward, not to the side.
• The arm that is up should maintain an angle of 45° off the midline of the body at all times.
• The shoulders and hips should remain parallel with the floor at all times.
• There should be no significant movement of the low back. The movement of the leg needed to draw the letters of the alphabet should come from the hip.
• The lower leg should move as a unit with the thigh. It is not good technique to just use the lower part of the leg .Draw the navel toward the spine throughout, but do not disrupt respiration by over-recruiting the transversus abdominis.

• Perform as many repetitions as possible with perfect form before switching sides. This is indicated in your Reps column as Max. When you can perform the alphabet on either side with perfect form, add a 1 lb. weight to each wrist and a 3 lb. weight to each ankle.

In a future article, I will discuss such key concepts of Outer Unit training as:

• Why outer unit training is essential to spinal and extremity joint health
• How outer unit training effects postural alignment
• Nervous system programming with outer unit training
• Functional anatomical correlation’s with extremity muscles and outer unit core muscles as related to improving work and sports performance

CONCLUSION

Inner unit training provides essential joint stiffness and the stability needed to provide the large prime movers of the body with a working foundation. When outer unit or prime mover exercises are executed in absence of a functional inner unit, poor posture, unwanted aesthetic changes and musculoskeletal injury are inevitable. For optimal health and performance, the inner unit must not only be functional, but must be maintained with technically correct exercise protocol.

REFERENCES:

1. Bogduk, N. & Towmey, L. (1987). Clinical Anatomy of the Lumbar Spine. Churchill Livingstone.
2. Richardson, C., Jull, G., Hodges, P. & Hides, J. (1999). Therapeutic Exercise For Spinal Stabilization In Low Back Pain. Churchill Livingstone.
3. Chek, P. (1999). Scientific Core Conditioning Video Correspondence Course. Encinitas: C.H.E.K Institute.
4. Chek, P. (1999). The Golf Biomechanic’s Manual – Whole In One Golf Conditioning. Encinitas: C.H.E.K Institute.
5. Chek, P. (1994). Scientific Back Training Video Correspondence Course. Encinitas: C.H.E.K Institute.