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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
- to describe the ideal standing posture
- to understand the mechanism of stability of standing posture
- to identify factors affecting standing posture
- Smith LK, Weiss EL, Don Lehmkuhl L (1996).
Brunnstrom's Clinical Kinesiology,
5th ed. Philadelphia, F.A. Davis. Chapter 12, pp. 401-410.
- 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
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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
- center of mass (COM): the weighed average of the center of mass of each body segments
- center of gravity (COG): the vertical projection of the COM to the ground
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Plumb line test -- side view
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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
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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
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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
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amount of deviation from the plumb line = extent of postural deviation
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Postural sway
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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
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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
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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
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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
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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
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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
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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 posturetorticollis
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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
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nutrition deficiency
before maturity ð postural faults
adult ð postural fatigue
poor habits
handiness
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Environmental Factors
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sports or hobbies
occupation or workplace
home environment
military training e.g. retracted posture
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Psychological Factors
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emotional factors e.g. depression or exciting
mental status e.g. mental retardation or Down's syndrome
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