To sum it up, I think the best way to exercise and safely use your core is to perform compound movements that require your torso to be straight and stiff while other joints move. For example, in a squat, you want your ankles, knees, and hips to be the primary “movers”, while you torso stays nice and tight to protect your back. So, to effectively use your core in compound movements, you need stiffness of the core, good posture in the spine, and mobility of the moving joints. If you want to read more about this, go ahead and click on the three links above.
Now, after that is said, we know that the core muscles are not best used when they are moving. Bending the spine in crunches, side-bends, and hyper-extensions may “work” the core muscles, but it will have very little carry-over to the big compound exercises, when you need to have a strong, stiff core. You’re just straining the spine when you incorrectly train your torso, all in the name of six-pack abs and vanity.
Now, there is another core muscle that might need some different attention. It’s called that transverse adbominis muscle. While the rectus abdmonis is for anti-extension, the lumbar erectors are for anti-flexion, and the obliques are for anti-lateral-flexion, the transverse abdominis (or, TVA) compresses the contents of the abdominal cavity. The TVA “draws your stomach in”, as if you’re trying to appear skinnier.
What is the purpose of compression of the abdominal cavity’s contents, then? Well, to keep it less gross than it needs to be, think of what happens when you’re sitting on the toilet. You’re contracting your stomach to “excrete” your bodily waste. This occurs with the help of the TVA. Gross, but true.
Another purpose for this compression is that, by keeping organs closer to your spine, the TVA helps with back pain. Basically, when you contract the TVA, your stomach is drawn in closer, meaning that your organs are closer to your spine. This gives your back a better mechanical advantage than if your TVA was relaxed and your belly and organs were pushed out. To explain why this works, go grab yourself a dumbbell, or something handheld-and-heavy. What’s easier to do: hold the dumbbell at your side, or hold it directly in front of you? Which position has the weight closer to your body? The same situation applies to your back and stomach.
For people who chronically let their guts “hang-out”, coaches and trainers may teach them to “isolate” their TVA, which is done by breathing air into one’s stomach, then forcefully expelling the air out of the mouth while drawing in the navel – as if you are trying to “suck in” to look skinny. Paul Chek, a health coach, talks about this in his book, How to Eat, Move and Be Healthy!
He also describes a technique that can help “drill” the “sucking-in” for some people. You contract your TVA and suck in a bit, then take an elastic exercise band, such as TheraBand, and tie it snugly around your stomach. If you relax and push your stomach out too much, then pressure from the band will remind you to contract your TVA.
Now, on to the greater purpose of the transverse abdominis. When you deadlift, what do you goes on in your abdominal cavity during the lift? Are its contents and organs just hanging out, all floppy, soft, and unsupported? No! What helps you maintain a strong, stiff core is not only your back muscles and abs, but your TVA. It creates this cool thing intra-abdominal pressure. Pressure inside your abdominal cavity is what keeps your core and torso stiff and straight – stiffness is needed for safe and effective use of your core.
To illustrate this, imagine taking two plastic water bottles, and emptying them. Leave one un-capped, and put the cap back on the second bottle. Bend and compress both of them. See the difference? The uncapped bottle is easily mangled, while the capped bottle can resist a lot of the force. Why is this so? Because the second bottle cannot lose its gas when it’s crushed because it’s capped – so, the attempt to decrease the volume of the bottle turns into an increase in pressure, which resists any change to the shape of the container. This is explained by the Ideal Gas Law in chemistry.
Pressure X Volume = (Constant Value) X Amount of Gas X Temperature
Everything on the right side of the equation stays the same, so when you decrease volume, pressure goes up.
Now, this whole illustration portrays what happens when you perform the deadlift. You go down and set-up for the lift, and right before you pull, you take in a deep breath, hold it in, and squeeze your abs. So, just like the capped battle, you increase the amount of gas in your belly, prevent any gas from “leaking”, and tighten your core. This results in a huge increase in intra-abdominal pressure. Had your core muscles (including your TVA) been relaxed, your stomach would have simply expanded, preventing pressure from increasing as if you were exhaling and letting air out.
The transverse abdominis simply prevents your stomach from expanding excessively so that the pressure inside your abdominal cavity increases. Now, your insides are taut and supported, including your spine. Remember, the bottle cannot bend when it is capped and filled with air. Imagine a stick dangling inside that bottle? It probably won’t get damaged or bent when you try to crush that bottle. This represents what happens with your spine. The intra-abdominal pressure keeps it protected from outside forces.
Now, go deadlift!