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The Standing Posture

Posture
Ideal Erect Posture
Stability of Erect Posture
Factors Affecting Good Posture

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Objectives¡G After studying this topic, the students will be able to

  1. to describe the ideal standing posture
  2. to understand the mechanism of stability of standing posture
  3. to identify factors affecting standing posture

  1. Smith LK, Weiss EL, Don Lehmkuhl L (1996). Brunnstrom's Clinical Kinesiology, 5th ed.  Philadelphia, F.A. Davis.  Chapter 12, pp. 401-410.
  2. Snijders CJ (2001).  Engineering approaches to standing, sitting, and lying.  In Nordin M & Frankel VH: Basic Biomechanics of the Musculoskeletal System.  Philadelphia: Lippincott Williams & Wilkins. Chapter 17, pp.420-427.

Posture

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Definition of posture

  • The Posture Committee of American Academy of Orthopedic Surgeons, 1947
  • posture¡G the relative arrangement of the part of the body
  • good posture¡G the state of muscular and skeletal balance which protects the supporting structures of the body against injury or progressive deformity irrespective of the attitude in which these structures are working or resting
  • poor posture¡G a faulty relationship of the various parts of the body which produce increased strain on the supporting structures and in which there is less efficient balance of the body over its base of support
  • Kendall et al, 1952
  • posture¡G a composite of the positions of all the joints of the body at any given moment
  • ideal posture¡G an alignment of maximum physiological and biomechanical efficiency, which requires a minimum of stress and strain
  • faulty posture¡G the posture that is not an ideal posture
  • Smith et al., 1996
  • a position or attitude of the body
  • the relative arrangement of body parts for a specific activity
  • a characteristic manner of bearing one's body
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    About ideal or good posture

  • Neither indicate the "averaged" posture nor the normal posture
  • regardless of body type or body size
  • related to range of motion, stability, muscle strength, endurance, training, and cueing
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    Ideal Erect Posture

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    Definition of erect posture

  • the posture that an individual is standing at attention or told to "stand up straight"
  • in this posture, a plumb line falls through the ear lob, the tip of the shoulder, center of the hip and knee, and anterior to the ankle joint
  • need conscious control
  • mistranslation from the Germany word of "normalstellung"
  • Braune and Fischer (1889) used "normalstellung" to indicate "upright reference", rather than erect posture (Smith et al., 1996)
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    Line of gravity

  • The line of gravity through the center of mass of the body
  • Note
    1. center of mass (COM): the weighed average of the center of mass of each body segments
    2. center of gravity (COG): the vertical projection of the COM to the ground
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    Plumb line test -- side view

  • The plumb line is placed just in front of lateral malleolus or through greater trochanter.
  • The individual to be tested is asked to take a few steps in place and then stand still with the feet at approximately the width of the hip joints, the arms relaxed at the side of the body, and the eyes looking forward
  • bony landmarks
  • through the calcaneocuboid joint
  • slightly anterior to the ankle joint
  • slightly anterior to the center of the knee joint
  • slightly behind the center of the hip joint
  • through the sacral promontory
  • through the bodies of the lumbar vertebrae
  • through the bodies of the cervical vertebrae<
  • through the odontoid process of the axis
  • through the external auditory meatus
  • slightly posterior to the apex of the coronal suture
  • surface landmarks
  • slightly anterior to the lateral malleolus
  • slightly anterior to a midline through the knee joint
  • approximately through the greater trochanter of the femur
  • approximately midway between the back and the abdomen
  • approximately midway between front and back of the chest
  • through the shoulder joint
  • through the lobe of the ear
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    Plumb line test -- front view or back view

  • the feet are equidistant from the plumb line
  • parallelity of the feet
  • standard posture¡G 3" apart + 10-15¢X of abduction of each foot
  • Kendall, 1970
  • level stance (at 0¢X of dorsiflexion)¡G 9¢X of abduction of the feet
  • wearing shoes (about 15¢X of plantarflexion)¡G 3¢X of abduction of the feet
  • through the midline of the body
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    Extent of postural deviation

  • amount of deviation from the plumb line = extent of postural deviation
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    Postural sway

  • the phenomenon of constant displacement and correction of the position of the center of gravity within the base of support (Smith et al., 1996)
  • components
  • anteroposterior (AP) sway¡G ~ 5-7 mm at quiet stance in young adults
  • mediolateral (ML) sway¡G ~ 3-4 mm at quiet stance in young adults ¡@
  • mechanism¡G the high center of mass of the human body and the small base of support in standing posture place the body in unstable equilibrium, resulting in constant displacement of the body pivoting about the ankle joint
  • high positive correlation was found between postural sway and incidence of falls in the elderly
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    Stability of Erect Posture

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    Ankle Stability

  • LOG passes anterior to the ankle joint and through the calcaneocuboid joint
  • active stability
  • calf muscle, especially soleus (Joseph, 1960)
  • to prevent the tibia forward rotation and ankle dorsiflexion
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    Knee Stability

  • LOG passes slightly anterior to the knee joint and just behind the patella
  • active stability
  • calf muscles, especially gastrocnemius
  • hamstrings
  • quadriceps¡G nor necessary (Basmajian, 1978), but some burst activity for postural sway
  • passive stability
  • anterior cruciate ligament
  • posterior capsule
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    Hip Stability

  • LOG may pass slightly anterior to, slightly posterior to,  or directly through the hip joint depending on postural sway and the pattern of stance
  • active stability
  • hip flexors and/or extensors accordingly (Schede, 1941)
  • passive stability
  • iliofemoral ligament
  • malalignment
  • sway back posture¡G hyperextension of the hip with posterior tilt of the pelvis and decreased lumbar lordosis
  • hyperlordotic back (hallow back)
  • flat back
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    Trunk Stability

  • LOG may pass slightly anterior to, slightly posterior to,  or directly through the vertebrae depending on postural sway and the pattern of stance
  • active stability
  • trunk flexors and/or extensors accordingly
  • passive stability
  • inert structure e.g. ligaments or capsules
  • malalignment
  • scoliosis
  • kyphosis
  • lordosis
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    Head Stability

  • LOG may pass slightly anterior to the atlanto-occipital joint
  • active stability
  • suboccipital muslces
  • passive stability
  • ligamentum nuchae to prevent anterior drop of the head
  • malalignment
  • forward head posture
  • torticollis
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    Factors Affecting Good Posture

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    Developmental Factors

  • developmental deviations
  • appear in many children at about same age and improves or disappear without any corrective treatment
  • are prone to develop habitual postures
  • if the condition remains static or if the deviation increases, then corrective treatment is necessary
  • characteristics of the child's posture
  • greater flexibility and mobility than adults
  • different growth rate in various tissues
  • bone growth more rapid than muscle growth ð soft tissue tightness
  • muscle strength imbalance ð muscle tightness
  • ligaments and fasciae tightness ðlimitation of ROM
  • infancy¡G growth in head and later in trunk
    age 2 to puberty¡G limbs growth > trunk growth
    after puberty¡G trunk growth > limbs growth
  • boys¡G shoulder girdle growth > pelvic girdle growth
    girls¡G shoulder girdle growth < pelvic girdle growth
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    Disease Factors

  • physical defects¡G visual, auditory, skeletal, etc
  • permanent disabilities¡G amputation, spinal cord injury, etc
  • muscle imbalance¡G shortening or weakness

  • theory of stretch-weakness vs. adaptive shortness (Kendall, 1969)
    muscles in the shortened positions (tightness) ð stronger
                    in the elongated positions (stretched) ð weaker
    muscle contracture or paralysis ð loss of motion ð deformity
  • pain¡G chronic pain, acute soft injuries, etc
  • neurological lesions¡G poliomyelitis, spinal tumor, CVA, etc
  • myopathy¡G muscular dystrophy, spinal atrophy, etc
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    Hygiene Factors

  • nutrition deficiency
  • before maturity ð postural faults
  • adult ð postural fatigue
  • poor habits
  • handiness
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    Environmental Factors

  • sports or hobbies
  • occupation or workplace
  • home environment
  • military training e.g. retracted posture
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    Psychological Factors

  • emotional factors e.g. depression or exciting
  • mental status e.g. mental retardation or Down's syndrome
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    Established on 12/30/2002 and Last Updated 01/02/2005 © 2004 Huei-Ming Chai, PhD PT          All Right Reserved