Sitting and the Nervous System

I am sitting on a plane as I begin to prepare for the first PHYT Movement Seminar at Crossfit Saol, PHYT To Run. I sit here crammed into a tiny seat, trying to type on a laptop that does’t quite fit, what better opportunity to talk about sitting? We must consider the impacts of sitting on movement and running mechanics. Have you ever thought about your daily activities as movement training? It’s a little scary, but why wouldn’t the body adapt to what you’re doing? I have been doing quite a bit of sitting adaptation training lately. Let’s look at the physical and neurological consequences of sitting, how it relates to running and performance, and how we can come up with an action plan to improve our movement and running!

The SAID principle: Specific Adaptations to Implied Demands.

It is a basic training principle. Your body will create adaptations to whatever specific demands are placed on it. That is fantastic when you are considering your strength/endurance training. Guess what? Sitting is a complex skill. You have to keep yourself upright against gravity while activating several group of muscles to stabilize yourself. If you’re sitting all day, guess what demands you are adapting to? Your body and nervous system are going to get exceptionally good at sitting! Unfortunately, the adaptations that make you efficient at sitting don’t transfer so well to running and other movements.

Demands of Sitting

With prolonged sitting, we are constantly in a fight with gravity to pull us down and forward. The more stacked your bony structures, the better the passive support (bone and ligament) and the less active support (muscle) you need. This is where all the good posture education theories comes in. Even with perfect posture, there are still muscles that must be turned on to keep you from falling and you are trying them all day every day. Take a look.

You better sit up straight?

You have several options on how to sit. For the purpose of this short article, I am going to look at two patterns and their effects in the sagittal plane only.


Slouched Sitting
If you scoot your butt forward in the chair and allow your pelvis to rotate into a posterior tilt (posterior tilt is when you take the front edge of your pelvis and it tilt it backwards so that the bowl of your pelvis rotates towards your belly button). In this position, my lumbar spine is now curved with a loss of its neutral lordotic curve. This rounded back position may place more passive stress on the ligamentous structures of the spine and is often implicated in back pain and injuries. To couple this, my thoracic spine now rounds out and my neck pushes forward into a forward head posture. This is bad posture 101.


Over Extended Sitting

In an effort to counteract this slouched posture, we do the opposite and overextend. Now you will see the lumbar spine hyper extended, pelvis tilted forward (anterior pelvic tilt), and the sternum and rib cage elevated. This decreases the ligamentous stress on the posterior aspect of the lumbar spine, which isn’t a bad thing. To perform this, we have to become efficient at using the muscles that hold us in that position, our spinal extensors and hip flexors. The spinal extensors contract to keep your lumbar spine from rounding and your head falling forward. Your hip flexors in the front compliment this by pulling their attachment on the front of the lumbar vertebra toward their attachment on the upper part of your femur. This compliments the position of lumbar extension.

In my opinion, neither of these sitting postures are a problem in isolation. It is only a problem if you are stuck in one pattern only. We need to have the ability to bend and extend to move efficiently. I see athletes that over-extend and are unable to flex everyday in my practice. If you can’t touch your toes, I may be talking to you.

Muscle Activation Patterns

Let’s run with the theory that by sitting in an upright position you are training an efficient use of these muscles 4…6…8 hours a day. Your nervous system is primed for use of efficient movement through spinal extension and psoas (hip) activation.

Think for a second and guess which muscles your nervous system may go to first when you ask it to hinge the hips, sit up out of bed, squat, run? Spinal extensors and hip flexors, ohh and if they’re turned on guess what you’re not using – Abs and glutes. There is this cool nervous system function called reciprocal inhibition. Simplified, if you want to bend your elbow, the bicep has to turn on and the tricep has to relax in order for your elbow to be able to bend. If both sides were on fighting each other your elbow wouldn’t move. So at the pelvis, if my hip flexors in the front are on, then glutes in the back are off. If my spinal extensors in the back are on then my abs in the front are going to be off, make sense? Here’s my million dollar question, if your abs and glutes are reciprocally inhibited can you ever get the most out of your workout? It’s a nervous system thing!

Flexibility Considerations

Remember folks, it’s about the nervous system. We always want to talk about tight muscles but the reality is they aren’t tight, they are guarded. Your nervous systems has sensory receptors in the muscles called muscle spindles. These receptors monitor stretch. When the spindle feels it is getting stretched too far, it will trigger the muscle to contract as a protective mechanism. One of the major functions of the muscle is to protect the nerve. In this respect, feeling tight is really your body’s way to protect you from injury. Sometimes that threat is real and sometimes it is perceived.

Let’s trace a nerve from the base of your skull where it exits your brain to the tips of your toes. Let’s pretend it’s a rubber band. Think about the length of that rubber band in sitting. Head is forward, chin is up, back is arched, pelvic is tilted forward, hip is flexed, knee is flexed, and ankles are in a neutral to plantar flexed position. This rubber band is in this position the majority of the time. Now, all of a sudden you want to go into a forward fold for the first time in days. That nerve gets afraid it is going to snap. It puts on the red flags to say whoa stop stretching! It tightens your hamstrings keeping the knee from straightening and your back extensors turn on so it can’t round and your chin stays up. Starting to see why you can’t touch your toes again? Don’t get me wrong I think there is a genetic component to the amount of stretch a person’s ligaments, joints, and muscle receptors will stretch before those red flags go off, but in general, I think spending the bulk of your day in a shortened position significantly increases the perceived nervous system threat to movement. If you don’t spend time in a position, your nervous system has a fear that something is going to snap. Muscles contract to protect the stretch on the nerve.

What’s That Mean With Running

Look at the mechanics of really good runners.

You can see their core is engaged, beautiful fluid spine motion, effortless rotation allowing powerful activation of the glutes. There is nothing stiff or static about them. They certainly are not stuck in extension. Extension is going to rob rotation and THAT is robbing power.

Try this: arch your back into extension and tilt your pelvis forward into anterior pelvic tilt as much you can. Sustain the anterior pelvic tilt position and lumbar extension and try to rotate as far as your can. Now flip it, posterior tilt your pelvis, relax your lumbar spine and rotate. Which went further? I’ll bet the posterior tilt position allowed significantly more rotation. Extension robs rotation and rotation is power.

Action Plan

Taking a clinical theory and trying to practically execute is admittedly hard. Especially, when you consider the amount of time you spend exercising vs time spent training a seated posture. Is a one hour reset 3 times a week enough to undo an entire day of poor posture? I don’t know. What if on top of that all your training is done in an extension pattern? Are you continuing to reinforce the same pattern? I don’t know for sure but it sure is thought provoking. You are starting to see groups like the Postural Restoration Institute demand all day focus and Ido Portal talking about 6+ hours of training a day. It would be perfect, but again, as I sit here on this plane it’s obviously not a reality all the time.

Nervous System Resets

In order to get out of the preferred extension pattern, we need to have a way to reset the nervous system. It’s easier said than done. There are a host of factors that play a roll. I believe a training background, body structure, inflammation, and injury history all play key factors in how we move. Constant contraction of postural muscles = energy crisis = inflammation = pain = nervous system saying stop!

If you are active with your mobility work, you have done resets in the form of contract relax stretching, foam roll work, loaded stretching etc. I want you to focus on nervous system pattern training. In this example we are going to focus on getting out of lumbar extension and anterior pelvic tilt. Remember, we need to trick those muscle spindles to relax if we are going to train in new ranges of motion. That is why contract relax stretching is so effective. It takes advantage of of the nervous system (I like Integrative Dry Needling too). Contract-relax stretching or relaxation/breathing techniques of the hip flexors and lumbar extensors are going to be the ticket. Once you get them to turn off you will be able to more effectively activate your abs and glutes (remember the principle of reciprocal inhibition). So follow with exercises or movements that reinforce activation of anterior core and glutes. Maybe throw in some loaded range of motion or positional training so that your joint receptors and muscle spindles begin to feel safe in that new position. We are training the nervous system.

If you made it this far thanks for reading! I hope you enjoyed and found value in at least a couple of the key concepts I discussed. If so, please let me know with a like or a share. I love feedback, so let me know what you thought, good or bad. If you have questions ask! Let’s get them answered! I am excited to explore this realm of sharing knowledge with my new venture!

Until next time keep moving and keep learning.

Nick Sanders DPT, CSCS, IDN
October 4, 2016