Don't ask why the pine trees in the front garden are knarled and crooked.
The straightness they were born with is right there inside them."
-Soseki

Sensory Motor Amnesia - How Does it Occur?
Over time with habituation!
A loss of integration within the feed back loop of brain-nerve-muscles.

Some Examples
STRESS - Involuntary Muscle Tension
Often experienced in the neck and shoulders. So many of us catch ourselves with shoulders elevated. We bring them down, and moments later, there they are again up by our ears. The abdominal and chest region are affected by stress resulting in shallow breathing which adds more tension.
Guarding Reaction to pain, fixation due to injury-trauma, post surgery, muscles reflexively tighten to immobilize and protect the traumatized area.

The Less Obvious The neck tension / ankle connection.
An ankle injury can develop into neck pain. Taking weight away from a left sided injury, one leans to the right. An automatic counter movement occurs. The muscles on the left side of the neck activate to keep ones head straight and maintain equilibrium.



A typical case history at age 35.
age 22 - Neck-Shoulder, tension ache
age 27 - Arm fatigue
age 32 - wrist pain, inflamed and chronic

Repetitive Motion strain, fixation - for example, computer key board use.
Carpal Tunnel Syndrome is pressure of the nerves and tendons as they pass through the wrist canal. A protocol for carpal tunnel might take the following movement sequence.


The same would be so if the mouse ache was in the neck shoulder region. A very similar procedure in movement patterns would be used because of the interconnectedness of the muscle groups whilst glued at the computer.



STOP!   
Front Flexors   
Startle Response   
to withdraw.   

   GO!
   Back Extensors
   Action Posture
   to rise - forward.

The combination of the above opposing reflexes tend to center at the middle of the body, yet they affect the entire musculature and the central nervous system. Ideally, when one set of muscles activate, the opposite let go. But overtime, one or both reflex patterns habituate and become fixed in the neuro - muscular system.
These muscle groups affect the oblique waist muscles. Much attention is given to the abdominal - back - waist muscles. This group of muscles, back - front - side, lose their interactive balance, acting like over tight or loose thongs. In some, the imprint becomes so strongly habituated, creating the bodily posture and restricted movement noticed in many seniors.

Somatic Retraction - “Luv Handles”

“Oh look Ted! I’m shorter than I used to be.”
“Well, Martha dear, you are getting older!”

The answer that Ted gave to Martha is the believed myth that shrinking goes with aging just as senile posture is accepted as the norm.