Transcript Postural muscles

Engineering Approaches to
Standing,Sitting and Lying
Biomechanics of Standing
Postural muscles
• Act predominantly to sustain your
posture in the gravity field.
• Contain mostly slow-twitch muscle
fibres
• Have a greater capacity for
sustained work.
• They are prone to hyperactivity.
• They tend to shorten in response to
over-use, under-use or trauma
Phasic muscles
• Contain mostly fast-twitch muscle
fibres
• More suited to movement.
• They are prone to inhibition.
• They are also more easily fatiguable.
• They tend to lengthen and weaken in
response to these types of stimuli
Do you know?
• What is Difference between two types of
muscles?
• Which of them are stronger?
Postural v/s Phasic
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Morphological changes are not very marked
Postural muscles are stronger ,can generate more power
Ratio of force production in posture to phasic is 3:2
Exercise and training can change this ratio up to 5:1
Imbalance Between Postural and
Phasic muscles
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Musculo-skeletal imbalance
Joint instability
Pain
Poor posture
Distal/Lower cross syndrome
• joint dysfunction L4-L5 and L5-S1 segments
• SI joint, and hip joint.
Postural Changes
• Anterior pelvic tilt,
• Increased lumbar lordosis,
• lateral lumbar shift,
• lateral leg rotation
• knee hyperextension
Upper/Proximal Crossed Syndrome
joint dysfunction
Atlanto occipital joint,
C4-C5 segment,
Cervicothoracic joint,
Glenohumeral joint,
T4-T5 segment
Postural Changes
Forward head posture
Increased cervical lordosis
Thoracic kyphosis
Elevated and protracted shoulders
Rotation or abduction
Winging of the scapulae
FORCES ACTING ON FOOT
The Ankle and Foot Joints
Function of the foot
• Provide a stable platform
• Generate propulsion
• Absorb shock
Bones
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Ankle + foot = 28 bones
foot = 26 bones
Leg: tibia, fibula
Foot:
– Tarsals (7): talus, calcaneus, navicular, cuboid, and
cuneiforms (3)
– Metatarsals (5)
– Phalanges (14)
Joints
• Tibiofibular:
– articulation between tibia and fibula
• amphiarthrodial joint
• Ankle joint
– Talocrural
• articulation between talus and tibia; talus and
fibula
• classified as a ginglymus
Joints
• Subtalar joint
– articulation between
talus and calcaneus
– classified as arthrodial
(gliding) joint
• Transverse tarsal
joint
– articulation between
talus, navicular,
calcaneus and cuboid
bones
– classified as arthrodial
joint
Joints
• Tarsometatarsal
– tarsal bones and metatarsal
– classified as arthrodial (gliding)
joints
• Metatarsophalangeal
– metatarsals and phalanges
– classified as condyloid
• Interphalangeal joints
(proximal and distal)
– phalangeal bones
– ginglymus
Arches of the foot
• Medial longitudinal arch
– calcaneus, talus, navicular,
cuneiforms (3), and medial
metatarsals (3).
• Lateral longitudinal arch
– calcanueus, cuboid, lateral
metatarsals (4 & 5)
• Transverse arch
– across metatarsals
Classifying Arch Type
• Pes Planus: Flat foot
• Pes Cavus: High Arch
• Normal
Movements
• Ankle joint
– dorsiflexion: “raising the toes”
– plantarflexion: “point the toes”
• Subtalar & Transverse tarsal joints
– Calcaneal inversion and eversion
• Interphalangeal joints
– flexion
– extension
Movements
• Supination
• inversion
• plantar flexion
• adduction
• Pronation
• eversion
• dorsiflexion
• abduction
Centre of Gravity & Centre of
Pressure
• Point of application of resultant force
on feet is called centre of pressure
• Centre of pressure may change with
swaying
• COP is located in front of ankle axis
• In standing calf muscles are always
active
Stability of foot
• Heel of a shoe act as shock
absorber
• Sole must be thin to give
good flexibility
• Angle of inclination
determines the weight that a
person loads on fore foot
• When height of heel is same,
size of foot determines the
weight
Do you know?
High heels can cause postural problems
that can lead muscle imbalance and pain
What is the maximum height of heel that
can be wore?
Stability of foot
• A women with small foot if
wears high heel,the angle of
inclination may increase upto
40*
• This angle should be 1014*,which means height of heel
should be maximum 3-4 cm
Claping of foot during walking
Stability of foot
There points at which the
weight acts
Two points anteriorly give
stability
One point posteriorly is
responsible for
unstability
Reaching
•Pelvic in maximum stability
•Centre of gravity is close to
line of gravity
•Hand and eyes should be in
comfortable position
Biomechanics of Pelvis
• Spine can bear compression forces
because they are in longitudinal
axis of spine
• SI joint surfaces are parallel to
these forces so they are prone to
shear forces
These forces are compensated by
• compressive action of muscles
• Side support of ligaments
Flat versus Ball and Socket joint
• Ball and socket joint can better bear transverse
forces
• Flat joint can better bear bending forces.
• Muscle forces that cross
SI joint can produce
compression
• Ligaments and fascia
perform same function
• This protection of lateral
movement of pelvis give
stability to SI joint