Since the beginning of time, mankind's argued, debated, and beat each other over the head with sticks, all in an effort to figure out who's right. Diesel engines vs. gasoline engines, Republicans vs. Democrats, Pepsi vs. Coke, Pamela Anderson vs. Carmen Electra – it's hard to get anybody to agree on much of anything these days.

The exercise industry is no different. In fact, I think the exercise industry is one of the worst offenders. Free weights vs. machines, high-intensity training vs. volume training, this diet, that diet, my diet, your diet – will it ever end?!? I doubt it, and to tell you the truth, I enjoy it. It makes things far more exciting than if everyone agreed.

During my 18-year career, I've been teaching people about the importance of drawing the abdominals inward while lifting, especially while performing functional lifts such as the squat and the deadlift. As you'd expect, some authors firmly state the opposite – that you must push your abdomen outward while performing such lifts. While I don't plan on going into reasons why I firmly disagree with this practice, I believe I need to clear up some confusion as to why drawing the belly button in during functional lifts such as the squat, deadlift or standing cable (pushing and pulling) exercises, can sometimes look as if the abdominals are pushing out.

Again, let me reiterate that I vehemently oppose the practice of actively pushing the abdominals out during a lift, but for those of you who have read Back Strong and Beltless and are drawing your abs in while lifting, I'll offer an explanation as to why it may appear that your abs are still being pushing out. First, here's a quick refresher.

The Deepest Abdominal of All

Behind your six-pack and beyond your obliques lies your Transversus Abdominis, otherwise known as the deep abdominal wall. The fibers of this important muscle run horizontally around your midsection, much like a corset or internal weight belt. Due to the insertion points and fiber orientation of this muscle, its contraction can only draw your belly button inward toward your spine (Figure 1). If you haven't tried it before, you should. The simple act of trying to draw your belly button toward your spine is one of the more important movements you could do while lifting. Without getting too technical, suffice it to say that this movement helps protect your spine from injury while lifting and acts to stabilize your torso. How does it do this? There are primarily three mechanisms.

1) When you contract your TVA by drawing your belly button inward, your internal organs are compressed creating intra-abdominal pressure (Figure 2). Although current research indicates that intra-abdominal pressure may not be as supportive as previously believed, it would appear that it works synergistically with the other mechanisms to help stabilize and protect the spine.

2) The TVA wraps around your midsection and attaches to thick connective tissue called thoracolumbar fascia (TLF). This connective tissue sheath is strongly anchored at each of your lumbar vertebra which, when pulled laterally by the contracting TVA, stabilizes each lumbar vertebra and creates something called hoop tension (Figure 3)(1).

3) Our erector spinae muscles are surrounded by the same connective tissue sheath that attaches the TVA to the lumbar vertebra, the thoracolumbar fascia. When we draw our belly button inward and contract our TVA, we pull the thoracolumbar fascia tight, including the portion that encases our erector spinae. As you know, a contracted muscle expands, or "gets bigger." When our erector spinae muscles contract within the now taught fascia, pressure is exerted against this tissue which creates an extension force, especially on a flexed spine. This is referred to as the hydraulic amplifier mechanism (1,2) because of the force created (muscle contraction) within a relatively small space (surrounding fascia).

There you have it, TVA 101 – the basic course in how drawing your navel inward contracts your TVA which helps stabilize your lumbar spine and protect it from injury.

"So if I'm drawing my navel in when I squat, why does it look like it's pressing out?" Good question. Here's a good answer.

Abdominal on the way out

There are two things that happen during a squat that will create the appearance of your abdominals pushing out. However, as I will show you at the end of the article, if done correctly it's possible to squat and have your abdominals move slightly outward even though you're still providing maximum protection of your lumbar spine.

The Diaphragmatic Reason

When we breath correctly, our large and relatively strong diaphragm muscle contracts with inhalation, which results in the diaphragm having a lower position in the thoracic and abdominal cavities, pushing the internal organs downward. Having nowhere else to go, our organs get pressed outward, which causes our abdomen to expand (Figure 4) . (Most of us are so self conscious about having a "big gut," that we limit our breathing to our chest which causes a number of other problems that are far too numerous to go into here.) Our diaphragm pressing down on our internal organs partially explains why our abdominals appear to push out while we're squatting, but here's the theory behind why this happens.

Many anatomists and biomechanic specialists agree that the body is a highly efficient and energy-conserving mechanism. This is why we so quickly adapt to a particular exercise program and need to constantly change our routine: the body gets "good" at performing a particular exercise to conserve energy.

While squatting or deadlifting, especially when going heavy, there's an increased demand to stabilize the spine near the bottom of the movement, sometimes known as the "sticking point," or point of least mechanical efficiency. As the progressive demand for stabilization increases, the powerful diaphragm contracts to stabilize the torso, which forces our internal organs down and out, making it appear as though our abdominals are being pushed out.

However, if you're making a concerted effort to keep your belly button drawn in while your diaphragm is trying to push them out, your body is following the laws of energy conservation. Here's how:

As the abdominals are being pushed out under the force of contraction from the superincumbent diaphragm, the TVA will be forced to work eccentrically. Most of you know that a muscle is approximately 30-40% stronger eccentrically than it is concentrically. Therefore, this process not only serves to effectively stabilize your spinal column, but since you're eccentrically using the TVA, it does so at a reduced energy cost! Viewed from the side, the action of the diaphragm will produce a slight outward movement of the abdominal wall.

The Rectus Reason

The heavier we squat, the more gross stabilization we need from our body, especially near the sticking point of the movement. The segmental stabilization of our spine is achieved by our Inner Unit (TVA, multifidus and pelvic floor and diaphragm) while gross stabilization and movement is provided by our Outer Unit (rectus abdominis, erector spinae, obliques, lats. etc.). When the load is relatively light, our Inner Unit can provide sufficient stabilization, but as the load progressively increases, we have an increased demand for our Outer Unit to work for gross stabilization.

As we descend into a squat with a heavy load, the increased lever arm against the spine will require an increasingly greater contraction of our erector spinae muscles to help our legs move the load. The stronger the back muscles contract to produce the extension force needed to move the load, the stronger the rectus abdominis and oblique muscles will contract. If they didn't, the spine would collapse into extension, which could get ugly. This co-contraction of the abdominals against the contraction of the back muscles provides us with the gross stability, or rigidity of the torso, needed to assist our legs in moving the load.

Again, a contracted muscle equals a thicker or "bigger muscle." Because the rectus abdominis is contracting, it's becoming thicker and may aid in the appearance of the abdominals moving outward. That's the second reason.

To quickly summarize, the appearance of the abdominals pushing outward is caused by (1) the force of the diaphragm causing the TVA to work eccentrically which pushes the navel away from the spine and (2) the thickening of the rectus abdominis while it contracts to assist with gross stabilization. However, in a properly functioning body, the Inner Unit musculature can remain contracted (abs in), while the Outer Unit does its job, particularly at high intensities, which results in the abs moving out.

So then, how do I Squat?

At the initiation of the squat, with the bar on your back, take in a deep breath and draw your belly button in toward your spine. This will serve to stabilize your spine via the mechanisms listed above. As you descend into the squat, make a conscious effort to keep the navel drawn inward the entire time (Figure 5) .

If you can't keep it in, you'll know right away and your gut will pop out – way out. (The outward movement I've been discussing in this article is minimal, but enough to have caused some confusion with people.) If you're unable to maintain your navel drawn inward and your gut pops out while squatting or deadlifting at less than 60% 1RM, chances are you will not be able to maintain contraction of the deep abdominal wall during more intense lifts, which is when the TVA is vital for the stability and safety of your spine!

As you press the weight back to the starting position, slowly release the air from your lungs through pursed lips (like you're blowing on a trumpet), which will maintain your TVA contraction without overloading the left ventricle of the heart. I recommend you follow this procedure for each rep of your set, especially during heavy sets.

Conclusion

The critical factor with regard to stability and longevity of the spine in lifting heavy loads is the proper sequence of events we use during a lift. In the functional body, the navel will move inward as an indicator that the segmental stabilizing mechanisms are activated (3). As we increase the demand for greater stiffness and stabilization of the torso, the diaphragm will force the TVA to contract eccentrically.

Along with this action is an increased activation of the rectus abdominis and oblique muscles, which provide gross stability via co-contraction against the spinal extensors. This will be recognized as the abs moving outward, during which time the inner unit muscles should continue to be active. This is unless, of course, the lifter is wearing a weight belt. As I've discussed in previous articles, belt wearing may completely alter the recruitment patterns of the core musculature, which may provide gross stability for the torso, but no additional stability for the spine!

Our world is laden with disagreement on just about any issue people can muster up. While some people tell you to press your abs out when you squat, others, including me, say you should draw your abs in to provide optimal protection of your lumbar spine and prevent an injury from occurring, ultimately increasing the longevity with which you can lift weights.

Hopefully this article has helped added a little clarity to the "abs in/abs out" debate that seems to have become more prevalent in gyms and Internet news groups.

References

1. Bogduk, N. Clinical Anatomy of the Lumbar Spine and Sacrum. (3rd. Ed.)
New York: Churchill Livingstone, 1999.

2. Gracovetsky, S., Farfan HF, Lamay C (1997). A mathematical model of the lumbar spine using an optimal system to control muscles and ligaments.
Orthopedic Clinics of North America 8: 135-153.

3. Chek, P. Scientific Core Conditioning. (correspondence course) Encinitas, CA: Chek Institute, 1993, 1999.