BASIC BIOMECHACNICS OF POSTURE FOR PHYSIOTHERAPY STUDENTS UG & PG

1. BIOMECHANICS OF
POSTURE

2.  TO KNOW ABOUT POSTURE
 TO KNOW ABOUT DEFINITION
 TO ABOUT TYPES OF POSTURE
 TO UNDERSTAND ABOUT BIOMECHANICS OF
POSTURE
 KINETICS AND KINEMATICS OF POSTURE
 BALACE AND POSTURAL CONTROL
 POSTURAL ANALYSIS AND EVALUATIONS
 ABNORMAL POSTURES

3. It is your power foundation- a stacked
framework from your feet through your
legs, hips, spine and shoulders to your
head”
Posture or position of greatest efficiency,
around your center of gravity, with muscles
on all sides, exerting pull.

4.  Posture can be defined as the relative
arrangement of different parts of the
body with line of gravity.

5.  In static postures the body and its
segments are aligned and maintained
in certain positions.

Eg –
Standing, kneeling, lying, and sitting

6. Dynamic
posture refers to postures in which the
body or its segments
are moving—walking, running, jumping,
throwing,
and lifting.

7. The study of any particular posture
includes kinetic and kinematic analyses of
all body segments.
Humans and other living creatures have
the ability to arrange and rearrange body
segments to form a large
variety of postures, but the sustained
maintenance of erect bipedal stance is
unique to humans.

8. Perfect posture pays dividends- by
reducing stress/loads which leads to
tension in the antigravity musculature,
degeneration of weight bearing structures,
less efficient movement, misalignment and
risk for injury.

9.  Erect bipedal stance gives us freedom for the
upper extremities, but in comparison with the
quadrupedal posture, erect stance has certain
disadvantages.
Erect bipedal stance increases the work of
the heart
Places increased stress on the vertebral
column, pelvis, and lower extremities
Reduces stability

10.  base of support (BOS), defined by an
area bounded posteriorly by the tips of
the heels and anteriorly by a line joining
the tips of the toes, is considerably
smaller than the quadruped base.

11.  center of gravity (COG), which is
sometimes referred to as the body’s center
of mass, is located within the body
approximately at the level of the second
sacral segment, a location that is
relatively distant from the base of support

12. Without appropriate neuromusculoskeletal
compensation and accommodation, such
actions result in imbalance and often
falling. Thus, postural deviations resulting
in balance problems lead to frequent strain
and injury to antigravity structures.

13.  one's entire weight can be considered as
concentrated at a point where the
gravitational pull on one side of the body is
equal to the pull on the other side. This point
is the body's center of gravity, and it
constitutes the exact center of body mass
When the center of gravity is above the base
of support and the pull of gravity is
successfully resisted by the supporting
members, an equilibrium of forces or a state
of balance is reached and no motion occurs.

14.  center of gravity is located in the region just
anterior to the top of the second sacral
segment; ie, about 55% of the distance for
women and 57% for men, from the plantar
surfaces to the apex of the head in the erect
position. Its location will vary somewhat
according to body type, age, and sex, and
move upward, downward, or sideward in
accordance with normal position movements
and abnormal neuromusculoskeletal
disorders.

15. The accumulation of fat and the loss of soft
tissue tone are common factors in altering
one's center of gravity. Thus, the center of
gravity shifts with each change in body
alignment, and the amount of weight borne
by the joints and the pull of the muscles
vary within reasonable limits with each
body movement. Adequate compensation
is provided for in the healthy, structurally
balanced person.

16.  LINE OF GRAVITY
 Reference Points. The vertical A-P line of gravity of the body, as
viewed laterally in the erect model subject, falls from above
downward through the earlobe, slightly posterior to the mastoid
process, through the odontoid process, through the middle of the
shoulder joint, touches the midpoint of the anterior borders of T2 and
T12, then falls just slightly anterior to S2, slightly behind the axis of
the hip joint, slightly anterior to the transverse axis of rotation of the
knee (slightly posterior to the patella), crosses anterior to the lateral
malleolus and through the cuboid-calcaneal junction to fall between
the heel and metatarsal heads. When viewed from the back, the
lateral line of gravity passes through the occipital protuberance, the
C7 and L5 spinous processes, the coccyx and pubic cartilage, and
bisects the knees and ankles. Thus, the A-P and lateral lines of
gravity divide the body into four quarters (Fig. 4.6).
Plumb Line Analysis. The plumb line, as used in postural analysis,
serves as a visual comparison to the line of gravity. For example,
when the plumb line is centered over S1, it should fall in line with the
occipital protuberance. In uncompensated scoliosis, however, it will
be seen to fall lateral to the occipital protuberance.

17.  BODY BALANCE AND EQUILIBRIUM
 Active and Passive States. Positions of the body that require
muscular forces to maintain balance are said to be in active
equilibrium, while those that do not require muscular effort are in
passive equilibrium. In passive equilibrium, all segmental centers of
gravity and the centers of all joints fall within the gravity line of the
body which must fall within the base of support. This requires
complete neutralization of all linear and rotary components of
gravitational force by joint surfaces and the base of support. Thus,
such a state is impossible in the erect position but possible in the
horizontal position.
Balance. When the forces of gravity on a body are in a balanced
position, the pull is equal on all sides about the center of gravity; ie,
its center of gravity is directly above its base of support and the body
is quite stable (Fig. 4.7). The amount of body mass outside this base
does not affect the equilibrium unless the center of gravity of the
mass is altered. If a part is laterally shifted to one side without a
compensatory shift of another part of equal weight, the center of
gravity is displaced sideward. The body will topple if the center of
gravity is displaced outside its base of support because gravity pulls
greater on the side of weight displacement. Because males generally
have a larger thorax, broader shoulders, and heavier arms than
females, they are toppled with less force than are females of the
same size.

18.  Common Torques. In the body, all partial centers of gravity or their
axes of motion do not coincide with the common line of gravity. In
fact, many partial centers are quite distant from the common line,
and this causes active rotary torques in many joints because of
gravitational pull which must be neutralized by antigravity muscles. A
weight-bearing joint is considered to be in equilibrium if the gravity
line of the supported structure is equal to the joint's axis of rotation. If
the gravity line is posterior to the joint's axis of rotation, the superior
segment tends to rotate posteriorly in compensation. If it is anterior
to the axis, the superior segment tends to rotate anteriorly.
Toppling Rate. The rate of movement of an unbalanced body
which is toppling depends on the amount of lateral displacement of
the center of gravity from its base of support. For this reason, a
toppled tree falls slowly at first because of trunk resistance and then
rapidly as its center of gravity is further displaced from the tree trunk.
A tall person falls harder than a short person. For the same reason,
the further the body's center of gravity is displaced from the midline
of its base of support, the more force is necessary to return it to the
balanced position.

19.  Aging- your body gradually loses its capacity to absorb and
transfer forces however its not aging that influences posture
as does:
 Inactivity/sedentary living/reluctance to exercise -leads to
loss of natural movement flow,
 Poor postural habits -eventually becomes your structure,
 Biomechanical compensation → muscle imbalance,
adaptive shortening, muscle weakness & instability within
the “core”,
 Body composition – increases load, stresses on spinal
structure, leads to spinal deviation,
 Workspace –ergonomics,
 Poor movement technique/execution/training ,
 Injury -leads to reduced loading capacity or elasticity,
 Others:

20.  Weight Bearing. The most economical use of energy in the standing position is
when the vertical line of gravity falls through a column of supporting bones. If the
weight-bearing bony segments are aligned so that the gravity line passes directly
through the center of each joint, the least stress is placed upon the adjacent ligaments
and muscles. This is the ideal situation, but it is impossible in the human body
because the centers of segmental links and the movement centers between them
cannot be brought to accurately meet with a common line of gravity.
Stability. Since the body is a segmented system, the stability of the body depends
upon the stability of its individual segments. The force of gravity acting upon each
segment must be individually neutralized if the body as a whole is to be in complete
gravitational balance. That part of balance contributed by an individual segment is
called the segment's partial equilibrium, as contrasted with the total equilibrium of the
whole body. Thus, each segment has its own partial center of gravity and partial
gravity line.
Position Changes. Any change in position of a partial center of gravity produces a
corresponding change in the common center of gravity. When the arms are raised
overhead and lowered, the center of gravity is respectively raised and lowered within
the body. When the arms are stretched forward or backward, the center of gravity is
respectively moved anteriorly or posteriorly within the body. When the trunk is flexed
severely forward or laterally, the center of gravity shifts outside the body.

22. Alignment May be tight May be weak Exercises
Mid back flexion Upper abdominals Thoracic extensors
Mid and lower trapezius
Active & passive
thoracic extension
Protracted scapulae Serratus anterior
Shoulder adductors
Shoulder internal
rotators
Mid & lower trapezius
Rhomboids
Stretch Serratus
Stretch Pectoralis minor
Narrowed intercostal
spaces
Intercostals Deep breathing
Multifidus
Quadratus lumborum
Titled scapulae Pectoralis minor Lower trapezius Stretch Pectoralis major
Stretch Latissimus dorsi
Elevated scapulae Upper trapezius
Levator scapulae
Lower trapezius Strengthen Middle &
lower trapezius
Stretch Upper traps &
Levator
Extreme neck
extension’
(Hyperextension)
Long Cervical
Extensors
Short neck flexors Strengthen neck flexors

23. Alignment May be
tight
May be
weak
Exercises
Anterior tilt Hip flexors Abdominals Stretch hip flexors
Strengthen obliques
for stabilization
Avoid full sit ups
Hip flexion Hip extensors Strengthen
gluteals
Extreme low
back extension
(hyperextension)
Low back
extensors
Stretch low back
extensors

24. Alignment May be
tight
May be
weak
Exercises
Posterior Pelvic
tilt
Hamstrings Stretch
hamstrings
Low back
flexion
Back extensors Strengthen back
extensors
Hip extension Hip flexors Strengthen hip
flexors

25. Alignment May be tight May be weak Exercises
Posterior pelvic tilt Hamstrings Hip flexors Stretch hamstrings
Strengthen hip flexors
Long kyphosis Upper abdominals External obliques
Upper back extensors
Strengthen upper back
extensors
Stretch and strengthen
abdominals
Narrowed intercostal
spaces
Intercostals Deep breathing
Hip extension Strengthen hip flexors
Extreme neck extension
(Hyperextension)
Upper trapezius
Levator scapulae
High cervical extensors
Neck flexors Stretch upper traps &
levator, strengthen mid
& lower traps,
strengthen neck flexors
Extreme knee extension
(Hyperextension)
Hamstrings
Calf
Strengthen hamstrings
and calf

26. 1. Static Postural Assessment
2. Dynamic Postural Assessment
3. Gait analysis
4. Flexibility assessment
5. Muscle testing
Once postural alignment is assessed the
focus should be on teaching and training
“Neutral Spine”

27.  Standing on both feet: front, side and
rear views
 Standing on one leg
 Sitting supported and unsupported
 Kneeling
 Supine
 Sleeping

29. Performing:
 A push- up
 A squat- with arms in front, lifting
overhead
 A lunge
 Walking
 Lifting

31. http://www.chiro.org/ACAPress/Body_Align
ment.html