The muscles involved in the postural system are muscles "tonic" located primarily in deeper location than the "phasic" muscles.
The "tonic" muscles have a structure making them suitable to a long contraction, protracted, while the "phasic" have the task of carrying out the rapid movements, typical in daily activities.
The phasic muscles are what we "see" and that is so important to our aesthetic image but the tonic ones, which you do not "see" are even more important because they keep us standing.

It depends on our personal history:

• Genetic factors
• Acquired factors:

• behavioral habits
• Working habits, or daily activities
• Sports practiced
• Traumas and diseases
• Mental attitude

Our body is a System in Dynamic Equilibrium with the fulcrum in the feet, our base of support.
It is defined as an Inverse Pendulum.

Postural stability depends on a complex system of control of the equilibrium (which substantially coincides with the system of control of the posture) that is realized through the continuous control of the tone of the postural muscles.
Assignment of the postural tonic system is to allow the body the postural stability, both in static position and in movement, suiting itself for the continuous environmental changes.

To realize such objectives the system uses a complex net of resources divided in 3 levels:

•  Sensorial receptors (cutaneous exteroceptive and proprioceptive, visual, vestibular and auditory) that sends information to the brain on the various parts of the body, in relationship to the same body and the environment.
•  Superior nervous centers that integrate and ri-elaborate the consequential data from the receptors, combining them with the cognitive process.
•  Nervous effectors centers from which the commands depart to the oculomotors and skeletal muscles for the continuous process of antigravity stabilization.