A good write from CrossFit South Bay on Midline Stability.

Good Midline.

Bad Midline.

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Midline Stability
Midline stability is the ability to control the muscles around your spine so that you can make it stiff and immovable. This sounds boring, but it is actually the opposite. This is the skill that allows us to deadlift, squat, run in pose, do kettlebell swings, and pretty much any other movement we do in crossfit. Getting better at this skill is one reason why crossfit transfers so well to other physical activities, like sports. Better midline stability means more control of your body. Think that might help you get better at snowboarding? Volleyball? Rugby? There are a lot of athletes at CFSB who think so; I’m just taking it one step further in explaining why these things help you beyond simply being stronger.
Ok, so what exactly is midline stability? Lets start with a bit of anatomy. Your spine is made up of a bunch of disks stacked on top of each other. Surrounding these vertically stacked disks are a series of long ropey muscles which also run vertically, these are your spinal extensors. Around your lower back you have your core muscles, which wrap up the middle of your body like a big belt around the cylinder of your abdomen. In your upper back you have a bunch of muscles around your scapula which are there to attach your shoulders to the rest of you. And that’s about it. You don’t need to worry about what the name of any specific muscle is, we don’t care about that when you are under a 400 lb squat. All we care about is that these muscles all do their job. What is their main job? To stabilize the spine, or, in other words, midline stability. When you are doing an athletic movement you need the spine to be rigid and stable. If it is not, you will either flex forward or extend backward in your spine during the movement. Worst of all you may have one of the disks slide over another disk. This is called shear force, and it is the most common mechanism for injury to the spine, especially as a result of exercising. All this can be avoided by getting really good at the skill of stabilizing your spine.
That’s right, stabilizing your spine is a skill. It may be the most essential skill we teach at crossfit. Every day you step into the box you are practicing this skill. I would guess that over 75% of the cues that crossfit coaches give have to do with improving spinal stabilization. It is that important. Doing things the right way is not only the safest way, but also the way in which you can achieve your maximum strength and power capabilities.
To give yourself a quick and dirty reference for midline stability lets do a short experiment. Put one thumb on your sternum, the other on the top button of your pants. If you are standing up straight, you are in a neutral back position. This is the position that we want to brace using our kick-ass midline stabilization skills. Now make your thumbs spread apart. That is what it feels like to do a spinal extension. You can feel how it’s not as stable as when you were in neutral. Imagine if that was the shape of your spine during a heavy back squat? Not so cool is it? That’s why the coaches are always on your ass to get tight and squat right. Bring you thumbs back to their original position (neutral) and then close down the space between your thumbs. This rounded back position is called back fluxing. You can imagine positioning your thumbs on your sternum and your top button during any exercise and immediately know if you are holding the neutral position, or have broken into a flexed or extended back position.
Without the motor control to stabilize your spine, nothing else really matters. Your tight (shoulders/ hips/ hamstrings/ ankles, etc) could be the reason why you can’t seem to position your overhead squat right, but you’d never know any of that if your core stabilization has the consistency of jell-o. Midline stability is our meat and potatoes (excuse the expression paleo friends). So as unexciting as it might seem, midline stability is the little piece of the crossfit puzzle is the one that makes every other part work.