Nerve Mechanics Part I

A diagram of the Human Nervous system.
Image via Wikipedia

Nerve mechanics, or neurodynamics simply means the study of the mechanical properties of nerves, how they stretch, move, glide, and cause pain as the body moves.  Science has made some exciting leaps forward in this area in the last twenty years,and these have been well summarized in some great books by Michael Shacklock and David Butler.  Amazingly, this work is almost completely unknown to most doctors and physical therapists.  This is unfortunate because nerve mechanics are easily understandable and help explain and treat a great many painful conditions.  Here are some basic facts that will help you understand this issue.  By the way, after reading this you will probably know more than your PT and doctor about musculoskeletal pain.


Nerves are Built for Movement

The picture to the right shows the major nerves of the body.  As you move around, those nerves need to slide, bend, elongate and withstand compression to allow the movement.  Fortunately, they are very well adapted for this task.   Notice the nerves that run from the neck to the tips of the fingers on the radioactive man.  When he bends his elbow, his ulnar nerve needs to bend around the point of his elbow, which causes it to compress and flatten out.  If he tilts his head to his left shoulder, you can see that this would pull on his nerves from above, causing them to slide upwards past any stationary adjacent bones or other physical structures.  He could pull on the nerves from below and slide them downwards by reaching his arm down and out while extending his wrist and fingers backwards.  What if he applied tension from both ends at the same time?  The nerves would simply have to elongate.  It does this by stretching just like a bungee cord, and in the process grows thinner.


Nerve Tension is a Body-Wide Phenomenon

A key point to note is that nerves cross many joints, and therefore movements that cause tension or relaxation of the nerve at one joint can cause tension or relaxation of the nerve at a distant joint or vice versa.  For example, by looking at the picture, you can see that the spinal cord goes from the top of the neck to the low back and then splits into the two sciatic nerves which run down the back of the legs and then turn into the common peroneal nerves which end in the feet.  There is a continuous line of pull from the top to the bottom and tension or slack at one end can be sensed at the other.


You can feel this easily by moving into a forward bend to touch your toes while moving your head and neck to stare at your navel.  When you go low enough, you will feel a familiar intense stretch at the back of the knee.  This is the sciatic nerve saying stretch no further (its not the hamstrings as most people think.)  You can greatly reduce the intensity of the feeling in the hamstrings by lifting your neck to look up.  This releases tension on the spinal cord from above and the resulting slack eases the tension on the sciatic nerve.  Move your head back and forth to feel how the neck position affects the feeling at the back of your knee.  It should be pretty obvious if you’re doing it right.  The point here is that your whole body is connected.  A lack of mobility in the neck can easily affect the low back or even the hamstring or vice versa.  The converse is also true.  You can reduce pain in one area by improving mobility in another.


Movement of the Nerves is Healthy

The movements of the nerves – bending, sliding, compressing and stretching – are completely normal and healthy under normal circumstances.  In fact, proper nerve function depends on movement – alternating tension, compression and relaxation probably assists circulation and reduces the nerve’s inner viscosity.  In other words, motion is lotion for the nerves just as it is for all the other parts of the body.  However, as you might have guessed, once the nerves become sensitive, moving then can cause pain.  In fact, a great many painful conditions that you may have thought were caused by a sore muscle or tendon such as carpal tunnel, plantar fasciaitis, tendonitis, a pulled hamstring etc, may actually be caused by sensitive, compressed or inflamed nerves.


In the next post we’ll discuss how nerves become sensitive to movement.

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4 Responses to “Nerve Mechanics Part I”

  1. I have been in severe pain the last 2 weeks It starts in the neck and goes down the arm and every nerve you show in the arm plus the nerve near the shoulder blade is hurting in the area. The elbow is is driving me nuts. what can I do to help relieve the pain.
    Thanl You

  2. Janet,

    Sorry to hear about the pain. Sounds like it is an irritated nerve. However, I’m not a doctor or physical therapist and am not qualified to diagnose or treat anyone over the internet. I would try to find a doctor or pt in your area that understands pain science and nerve mechanics. A z health or feldnekrais practitioner might also be of help. Good luck.


  1. Nerve Mechanics Part II « Better Movement - December 1, 2010

    […] the previous post I discussed some of the basics of nerve mechanics. To review, the nerves need to slide, bend, […]

  2. Nerve Mechanics Part III « Better Movement - December 2, 2010

    […] the first two posts on nerve mechanics I discussed how nerves move and how that movement can cause pain. This post is […]

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