This is an excerpt from Back Exercise by Brian Richey.
Most people think of the spine as a singular object. We call it our spine or spinal column, don’t we? But the spine is actually comprised of 25 individual joints (not including the coccyx) from top to bottom, and that only accounts for the vertebra to vertebra connections. In the thoracic region, you also have joints where the ribs attach, but that is for another book and another day. Each of these joints is made up of the top and bottom vertebra and the disc that sits between them. This is referred to as the spinal unit.
Understanding the spinal unit is important, especially when we begin talking about low back pain and specific spinal conditions. In looking at the spinal unit, you can see that each vertebra creates a joint that, depending on its spinal region, can rotate, and flex forward, back, and side to side. It also absorbs compressive (pushing together), tension (pulling apart), and shear (sliding) forces. Placing these spinal units together produces a spine that is strong and resilient yet still susceptible to injury.
We should mention something about “neutral spine” and spinal “bias.” I have had the pleasure of teaching thousands of fitness professionals for over 15 years. A question I ask that seems to stump the students is, “What is neutral spine?” The reason it stumps people is that, depending on the area of the fitness industry they are in, neutral spine may have different definitions. Pilates, yoga, bodybuilding, and general fitness professionals may all have slightly different ways to describe this concept.
The traditional definition that I learned years ago is that neutral spine is the posture of your pelvis in which the anterior superior iliac spine is in line with the posterior superior iliac spine. I probably just lost you, as most people have no idea what that means. Someone who has studied anatomy may understand this definition but it may not mean anything to the average person.
To help understand neutral spine, let’s demonstrate it. Lie down on the floor. Note how your low back feels on the ground. Do you have a high arch to your back, the sort of arch where a chihuahua could walk under it? Okay, to get to a more neutral state, flatten out your lumbar spine a bit. Think of the arch in your lumbar as a small foot bridge rather than the Golden Gate Bridge. On the other extreme, if your back is pressed completely flat to the ground, that is too flat. You need to have a slight arch in your spine. So, the rule of thumb upon lying down is that you want a small arch to your back as long as it doesn’t cause you discomfort or pain. That is your neutral spine. If it does cause you some pain, then find the position you can maintain without discomfort. For your body, that becomes your neutral spine. Even though it may not be the true definition of neutral spine, for your body, it is neutral. Over time, you may find that you are able to get closer to the traditional definition. This is called your bias.
Your directional preference, or pelvic bias, is the position of your pelvis relative to your lumbar spine that causes no additional pain or relieves pain symptoms. Some people feel better in a flat-back position; we call this spinal flexion or posterior pelvic tilt (see figure 1.6a). Other people prefer to be in more of an extended position with a larger arch to their spine; we call this spinal extension or anterior pelvic tilt (see figure 1.6b). Whichever position feels better for your body is your preference or bias. In fact, depending on your specific medical condition, you may need to exercise in your preferred bias in order to avoid pain. This preferred bias is your neutral spine.