Transcript Chapter 15: The Standing Posture KINESIOLOGY Scientific Basis of Human Motion, 10

Chapter 15:
The Standing Posture
KINESIOLOGY
Scientific Basis of Human Motion, 10th edition
Luttgens & Hamilton
Presentation Created by
TK Koesterer, Ph.D., ATC
Humboldt State University
Objectives
1. 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 factor that affect the stability and energy
cost for the erect posture
Objectives
4. 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
SIGNIFICANCE OF POSTURE
• Posture means position
• The multisegmented human body does not
have a single posture
• Most posture research has been related to
the volitional standing position
• A custom is to accept standing posture at a
person’s basic posture from which all other
postures stem
SUPPORT OF THE
STANDING POSTURE
Muscular Activity in Erect Standing
• Humans have a very economical antigravity
mechanism
• Muscle energy to maintain erect posture is
not great
• Ligaments play a major role in supporting and
maintain 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
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 the
anterior
Thigh & Hip: Very little activity
– Swaying produces bursts of ab/adductors
– Iliopsoas constantly active, preventing
hyperextension of the hip joint
Muscular Activity in Erect Standing
Spine: Very slight activity is sacrospinalis or
abdominals
Upper Extremity: low-grade activity in a number
of muscles
– Serratus anterior & trapezius support the
shoulder girdle
– Supraspinatus resist downward dislocation
of the humerus
– No activity in elbow or wrist joints, when
passively hanging
The Neuromuscular Mechanism for
Maintaining Erect Posture
• Proprioceptors are responsible for most of the
reflex movements to maintain posture
• Posture modification of posture depends on;
1. Voluntary decision towards change
2. Experience with desired posture
3. Instruction resulting in different strategies
4. Environmental influences
Postural Stability
• Hellebrandt (1940) “Standing is, in reality,
movement upon a stationary base”
• CG does not remain motionless
• Subjects were constantly swaying
• Today, force platforms can record postural
sway in magnitude, direction, and pattern
• Postural stability is currently measured as
sway motion between CG and center of
pressure
Alignment of
Body Segments
• “Good posture”
• Weight-bearing
segments balanced
vertically
• Rotary effect of
gravitational force in
minimized
Fig 15.1
Alignment of
Body Segments
•
•
•
•
“Fatigue posture”
Muscles have let go
Ligaments prevent collapse
Zigzag alignment of weight
bearing segments increase
rotary effect of gravitational
force
Fig 15.2
Alignment of Body Segments
• Even the most ideal posture have some
rotary force present
1. Supporting column of trunk being more
posterior
2. Support base (feet) being projected forward
3. Spinal column being curved anteroposteriorly
4. Chest forming an anterior load
– Females breasts are an additional anterior
load
Relationship of Alignment of Body
Segments and Integrity of Joint Structure
• Prolonged postural strain is injuries
– Ligaments can permanently stretch
– Cartilages can be damaged due to
abnormal friction
– Arthritic changes in weight-bearing joints
Minimum Energy Expenditure
• 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 or possible
FACTORS RELATED TO THE
STANDING POSTURE
Energy Cost
• “Fatigue posture”
• Requires a minimum of
metabolic increase
Knees - hyperextended
Hips – forward
Increased thoracic curve
Head – forward
Trunk - posterior lean
Fig 15.3
Evolutionary and
Hereditary Influences
• As man began to to walk upright
• There was a shift form a vertically suspended
position to a vertically support one
• Although no specific principle, changes had
to occur to the musculoskeletal structure
Strength and Flexibility
• Seem to be universally accepted relating to
the preponderance of strength and flexibility
exercises
– Strength of abdominals
– Scapula retractors
– Pectoral stretching
– Hamstring stretching
Age
• Several Physical and neurological factors
• Infant initially lack muscular strength and
neurological development
• The aging adult tends to alter posture
– Older people lean forward
• Bone mineral loss
• Muscular weakness
• Fear of instability
Psychological Aspects
• Atypical postures may be symptoms of
personality problems or emotions
– Emotional reaction to an abnormal posture
– Mental fatigue
– Depression, Joy, or Fear
• Evidence exist on the correlation between
mood state and performance (Huddleston et
al., 2000)
PRINCIPLES APPLIED
TO POSTURE
4. Form the point of view of energy expenditure,
good posture would seem to be a position
that requires a minimum expenditure of
energy for the maintenance of good
alignment
5. Good posture, in repose and in activity,
permits mechanically efficient function of the
joints
6. Good posture, both static and dynamic,
requires a minimum of muscle force
PRINCIPLES APPLIED
TO POSTURE
7. 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
8. Good posture requires good condition
– neuromuscular control & reflexes
9. Adjustments in posture can be made more
readily by individuals who have a good
kinesthetic awareness of postures they assume
and of the degree of tension in their muscles
PRINCIPLES APPLIED
TO 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. In the last analysis, both static and dynamic
posture of any individual should be judged on
the basis of how well it meets the demands
made upon it throughout a lifetime
POSTURAL ADAPTATIONS TO EXTERNAL
CONDITIONS AND SPECIAL PROBLEMS
Standing on an inclined plane: bending at
knees, hips, or spine adjust CG above the
base of support
• 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
– Comfortably wide stance in the direction of
motion
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
POSTURE
SCREENING
• An optimal standing posture
Line of gravity falls:
• slightly anterior to lateral
malleolus
• Midline of the knee
• Slightly posterior to hip
• Anterior to sacroiliac joints
Fig 15.3a
POSTURE SCREENING
1. Subject should wear minimal clothing
2. Subject assumes comfortable stance
3. Landmarks to line of gravity from the side
4. Alignment of foot, ankle, & knee from front
5. Alignment of spine & pelvis from rear
A screening matrix expedites observation of any
deviations
PRINCIPLES APPLIED
TO POSTURE
1. The weight-bearing segments of the body are
so aligned in good standing posture that
angles of inclination in the trunk and in the
pelvic girdle are within “normal” limits
2. In order to be stable, the intersection of the
line of gravity with the base of support will be
close to the geometric center of the base.
3. Good standing posture is a position of
extension of the weight-bearing joints.