Posture

Posture is alignment of the parts whether upright,sitting or recumbent. it is the attitude assumed by co-ordinated action of many muscle working to maintain stability either when the body is stationary or when it is moving.it is a position  in which you hold your body when standing  or sitting.

TYPES OF POSTURE

1. Inactive posture
2. Active posture- a) static posture; b) dynamic posture.

1)Inactive posture

• These are attitudes adopted  for resting or sleeping.
• Minimal muscular activity.
• Usually assumed in need of relaxation.

2) Active posture

Integrated action of many muscles is required to  maintain active postures. it can be either static or dynamic-

a) Static postures- 

• A constant pattern of posture.
• In static posture, the body and its segments are aligned and maintained in certain positions.
• In the erect postures they preserve a state of equilibrium.
• Examples of static postures include standing, sitting, lying, and kneeling.

b) Dynamic postures-

• It is required to form an efficient basis for movement.
• Dynamic posture refers to postures in which the body or its segments are moving- walking,running, jumping, throwing, and lifting.

POSTURAL STABILITY

• So long as the line of gravity from the center of mass falls within the base of support, a structure is stable.
• Stability is improved by lowering the center of gravity (COG) or increasing the base of support (BOS)

For postural stability here we include muscle and neurological control: influence on stability

A) Muscles: Influence on stability

• The intensity and distribution of the muscle work which is required for both static and dynamic postures varies according to posture.
• The groups of muscles, which are used to maintain the erect position, known as the anti-gravity muscle.
• The muscles of the neck and trunk not only act as prime movers or as antagonists to movement caused by gravity during dynamic activity, they are important stabilizers of the spine.
• Without the dynamic stabilizing activity from the trunk muscles, the spine would collapse in the upright position.
• Both superficial (global) and deep (core) muscles function to maintain the upright posture.

Muscles controlling the spine
1)Lumbar region-  superficial and deep muscle play critical role in providing stability and maintaining the upright posture

a)Superficial muscle

• Rectus abdominis
• External and internal obliques
• Quadratus lumborum (lateral portion)
• Erector spinae
• Iliopsoas

b) Deep muscle

• Transversus abdominis
• Multifidus
• Quadratus lumborum (deep portion)
• Deep rotators

2) Cervical region 

a) superficial muscles-

• Sternocleidomastoid
• Scalene
• Levator scapulae
• Upper trapezius
• Erector spinae

b) deep muscles-

• Rectus capitis anterior and lateralis
• Longus colli

B) Neurological control: influence on stability

Postures are maintained or adapted as a result of neuromuscular co-ordination, the appropriate muscle being innervated by means of a very complex reflex mechanism.

The postural reflexes- A reflex is, by definition, an efferent response to an afferent stimulus.

The efferent response in this instance is a motor one, the anti-gravity muscle being the principal effector organs. afferent stimulus arises from a variety of source all over the body, they are-

1. The muscles-  neuromuscular and neurotendinous spindles within muscles record changing tension, that causes stimulation and appears to be a manifestation of the myotatic, or stretch reflex.
2. The eyes- visual sensation records any alteration in the position of the body with regard to its surrounding
3. The ears- stimulation of the receptors of the vestibular nerve results from the movement of fluid contained in the semicircular canals of the internal year.
4. Joint structure- in the weight bearing position approximation of bones stimulates proprioceptive receptors.
5. Skin sensation- also plays a part, especially that of the soles of the feet, when the body is in standing position.

Impulses from all these receptors are conveyed and co-ordinated in the central nervous system( ex-cerebral cortex, cerebellum, red nucleus, vestibular nucleus.),  complex series of efferent response together constitute the postural reflex.

THE PATTERN OF POSTURE

Patterns of posture, both static and dynamic, are gradually built up by intergration of the many reflexes, which together make up the postural reflex.

A) Good posture

Posture is said to be good when it fulfils the purpose for which it is used with maximum efficiency and minimum effort.

An ideal standing posture would be one in which the body segments were aligned vertically and the LoG passed through all joint axes. Normally body structure makes such an ideal posture impossible to achieve, but it is possible to attain a posture that is close to the ideal, in an optimal posture.

Development of good posture

The chief factors which predispose to the health and development of the muscles and the postural reflex are-

1. A stable psychological background
2. Good hygienic condition
3. Opportunity for plenty of natural free movement.

A stable psychological background→ emotion and mental attitude have a profound effect upon the nervous system, and this is reflected in the posture of the individual. joy happiness and confidence are stimulating and are reflected by an alert posture, in which positions of extension predominate. conversely unhappiness, conflict and a feeling of inferiority have just the opposite effect.

Good hygienic condition→ particularly with regard to nutrition and sleep, are essential for healthy nervous system and for the growth and development of bones and muscles.

Opportunity for plenty of natural free movement→also encourage the harmonious development of the skeletal muscles.