Transcript 12.hamilton11e_ppt_15

Chapter 15:
The Standing Posture
KINESIOLOGY
Scientific Basis of Human Motion, 11th edition
Hamilton, Weimar & Luttgens
Presentation Created by
TK Koesterer, Ph.D., ATC
Humboldt State University
Revised by Hamilton & Weimar
© 2008 McGraw-Hill Higher Education. All Rights Reserved.
Objectives
Identify and describe the skeletomuscular
and neuromuscular antigravity mechanisms
involved in the volitional standing position.
2. Summarize the similarities and differences
that occur in the relation of the line of gravity
to various body landmarks with good and
poor anteroposterior segmental alignment.
3. Discuss the factors that affect the stability
and energy cost for the erect posture.
1.
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Objectives
Explain the effects that the variables of age,
body build, strength, and flexibility have on
the alignment of body segments in the
standing posture.
5. Name the values, if any, of good posture.
6. Perform kinesiological analyses on the
posture of individuals of different ages and
body builds.
4.
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SIGNIFICANCE OF POSTURE
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Posture means position.
The multisegmented human body does not
have a single posture.
Most posture research has been related to
the volitional standing position.
All posture is somewhat dynamic, including
postural sway during quiet standing.
Represents a person’s habitual carriage.
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SUPPORT OF THE
STANDING POSTURE
Muscular Activity in Erect Standing
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Humans have a very economical antigravity
mechanism.
 Muscle energy required to maintain erect
posture is relatively small.
 Ligaments play a major role in supporting and
maintaining the integrity of the joints.
 Muscles that are active are those that aid in
keeping the weight-bearing column in relative
alignment and oppose gravity.
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Muscular Activity in Erect
Standing
Foot: Only muscular activity is in the
push-off phase or rising on the toes.
Leg: Posterior calf muscles are more
active then the anterior.
Thigh & Hip: Very little activity:
Swaying produces bursts of ab/adductors.
 Iliopsoas constantly active, preventing
hyperextension of the hip joint.
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Muscular Activity in Erect Standing
Spine: Very slight activity in sacrospinalis or
abdominals.
Upper Extremity: low-grade activity in a number
of muscles:
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Serratus anterior & trapezius support the shoulder
girdle.
Supraspinatus resist downward dislocation of the
humerus.
No activity in elbow or wrist joints when passively
hanging.
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The Neuromuscular Mechanism
for Maintaining Erect Posture
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Proprioceptors are responsible for most of
the reflex movements to maintain posture.
 Posture modification depends on:
1. Voluntary decision towards change.
2. Experience with desired posture.
3. Instruction resulting in different strategies.
4. Environmental influences.
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Postural Stability
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Hellebrandt (1940) “Standing is, in reality,
movement upon a stationary base”.
CoG does not remain motionless.
Subjects were constantly swaying.
Today, computerized dynamic posturography
can record postural sway magnitude,
direction, and pattern.
Postural stability is currently measured as
sway motion between CoG and center of
pressure as well as CoG velocity.
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Alignment of
Body Segments
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“Good posture”
Weight-bearing
segments balanced
vertically.
 Rotary effect of
gravitational force is
minimized.
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Fig 15.2
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Alignment of
Body Segments
“Fatigue posture”
 Muscles have let go.
 Ligaments prevent collapse.
 Zigzag alignment of weight
bearing segments increases
rotary effect of gravitational
force.
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Fig 15.1
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Alignment of Body Segments
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Even the most ideal posture has some
rotary force present.
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4.
Supporting column of trunk situated more
posteriorly.
Support base (feet) project forward.
Spinal column curved anteroposteriorly.
Chest forms an anterior load.
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Females breasts are an additional anterior
load.
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Relationship of Alignment of Body
Segments and Integrity of Joint Structure
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Prolonged postural strain is injurious:
Ligaments can permanently stretch.
 Cartilages can be damaged due to
abnormal friction.
 Arthritic changes in weight-bearing joints.
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Minimum Energy Expenditure
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Cannot be accepted as the criteria of good
posture.
 Metabolic economy is desirable to a point.
 Well-balanced segmental alignment should
not be sacrificed for it.
 A single interpretation of an ideal posture is
neither practical nor possible.
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FACTORS RELATED TO THE
STANDING POSTURE
Energy Cost
“Fatigue posture” .
 Requires a minimum of
metabolic increase.
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Knees - hyperextended
Hips – forward
Increased thoracic curve.
Head – forward
Trunk - posterior lean
Fig 15.3
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Age
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Infant lacks muscular strength to stand
upright.
Posture in toddler more erect and less stable
than in older child or adult.
Postural sway becomes more variable with
aging.
Stability more dependent on vision, less on
proprioception in aging population.
Level of muscle activity increases as stability
decreases.
Increased tendency to fall with advanced age.
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Evolutionary and
Hereditary Influences
As man began to walk upright there was
a shift from a vertically suspended
position to a vertically supported one.
 Although no specific principle is derived,
changes had to occur to the
musculoskeletal structure.
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Strength and Flexibility
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Seem to be universally accepted factors
based on the preponderance of strength
and flexibility exercises:
Strength of abdominals
 Scapula retractors
 Pectoral stretching
 Hamstring stretching
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PRINCIPLES APPLIED
TO POSTURE
1.
2.
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Weight-bearing segments aligned so trunk
and pelvic girdle inclination is within
“normal” limits.
Line of gravity intersects center of base of
support.
Weight-bearing joints should be in
extension, balanced, no strain or tension.
Good posture requires minimal energy
expenditure for the maintenance of good
alignment.
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PRINCIPLES APPLIED
TO POSTURE
5.
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8.
Permits mechanically efficient function of the
joints.
Good posture, both static and dynamic,
requires a minimum of muscle force.
Good posture, both static and dynamic,
requires sufficient flexibility in the structure of
the weight-bearing joints to permit good
alignment without interference or strain.
Good posture requires good coordination.
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neuromuscular control & reflexes.
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PRINCIPLES APPLIED
TO POSTURE
Adjustments in posture can be made more
readily with a good kinesthetic awareness of
posture.
10. Good posture, both static and dynamic, is
favorable, or at least not detrimental, to
organic function.
11. The characteristics of normal posture change
with age.
12. Posture of any individual should be judged on
the basis of how well it meets the demands
made upon it throughout a lifetime.
9.
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POSTURAL ADAPTATIONS TO EXTERNAL
CONDITIONS AND SPECIAL PROBLEMS
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Standing on an inclined plane: adjustments
should be made at the ankle when possible;
adjust CoG above the base of support.
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Same for wearing high heels, pregnancy, and
carrying a heavy bundle in front of the body.
Standing on a moving surface: be prepared to
make adjustments to acceleration,
deceleration, and side-to-side sway.
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Comfortably wide stance in the direction of motion.
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POSTURAL ADAPTATIONS TO EXTERNAL
CONDITIONS AND SPECIAL PROBLEMS
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Strategies for postural adaptation:
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Hip strategy:
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Adjustments to maintain center of gravity over
base are made through hip and trunk
flexion/extension.
Ankle strategy:
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Adjustments to maintain center of gravity over
base are made through changes in ankle/foot
motion or position.
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POSTURAL ADAPTATIONS TO EXTERNAL
CONDITIONS AND SPECIAL PROBLEMS
Standing on one foot:
 Usually managed automatically by the
muscle, joint, and labyrinthine
proprioceptors, and reflex response.
 Shift body weight to supporting limb.
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POSTURE
SCREENING
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In an optimal standing
posture the line of gravity
falls:
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slightly anterior to lateral
malleolus
Midline of the knee
Slightly posterior to hip
Anterior to sacroiliac joints
Fig 15.3a
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POSTURE SCREENING
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Subject should wear minimal clothing.
Subject assumes comfortable stance.
Landmarks to line of gravity from the side.
Alignment of foot, ankle, & knee from front.
Alignment of spine & pelvis from rear.
A screening matrix expedites observation of any
deviations.
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Chapter 15:
The Standing Posture
© 2008 McGraw-Hill Higher Education. All Rights Reserved.