By: Dr. David Tiberio, Gray Institute

At the Gray Institute the term “mostability” is discussed very frequently.  In fact, it is considered a Principle or Truth of Human Function.  All movements are part MOBILITY and part STABILITY.  One without the other is sure to bring poor quality movements and potential injury.  Functional movements differ, but for each there is an optimal combination of mobility and stability that produces the MOST-ABILITY.

At the Gray Institute, to be considered a TRUTH of human movement, “mostability” can’t be an isolated phenomenon. It must be found in all forms of function.  It must be true at the “local” joint level as well as the “global” movement level.  Sometimes it is hard to recognize “mostability”, but it is a primary component of all successful movements.  Therefore it is critical that our examination and treatment schemes include an aspect of “mostability”.

A simple, but important example of “mostability” is the movement of the scapula on the thoracic cage during shoulder function.  As the arm is used, the scapula must provide a stable foundation for the muscles that move the humerus.  But the scapula must also move on the ribs in order to have full motion of the shoulder complex.  The scapula must be stable and mobile, at the same time!  If the scapula was fixed to the ribs with pins, it would be a stable foundation, but the lack of mobility would stress the gleno-humeral joint. At the other end of the spectrum, if the muscles connecting the scapula to the thoracic were cut, there would be plenty of mobility, but no stable foundation for the muscles to work from. “Mostability” is essential.

Just as important, but not as obvious is the “mostability” of the pelvis when our foot hits the ground in running.  At ground contact, the posterior-lateral muscles of the hip have a large role in decelerating the motions of the hip, knee, and foot created by gravity and ground reaction force.  These muscles need the pelvis to be a stable base from which to generate force, but the pelvis is moving.  So again, both stability and mobility are necessary.  During running, the one foot will be in the air when a stable yet mobile pelvis is required. How does the pelvis remain stable while it is moving without the connection to the ground?   The mass and momentum of the swinging leg, trunk, and arms all contribute to the ability of the pelvis to have “mostability”. This knowledge influences how train and rehabilitate clients who run.

All movement specialists need to determine whether their client lacks mobility or stability or both.  After the deficits that are inhibiting function are identified, a logical strategy is required.  Existing success can be leveraged to reduce or eliminate the “mostability” problem.  The 3D Movement Analysis and Performance System is comprised of global movements that assess both mobility and stability.  These Analysis movements establish a Relative Success Code (RSC).  Using the RSC to establish a logical sequence,, the global movements are to create training exercises.  By starting with “mostability” success and tweaking in a logical progression, success begets more success.