postural control Flashcards
posture
- also called “postural orientation”
- ability to maintain an appropriate relationship between:
1) body segments
2) body & environment
examples of relationship between BODY SEGMENTS (that will determine posture)
- between head and trunk
- between trunk and lower ex.
- between arm and forearm
t/n: their alignment w/ eao will determine posture
examples of relationship between BODY & ENV (that will determine posture)
- sitting on a chair
- lying on bed
t/n: orientation between body segment + body + environment =posture
quadrupedal stance vs bipedal stance
quadrupedal
- BW distributed in UE and LE
- ancient times
- ambulating/exploring env using (ALL 4) bilateral ex.
bipedal
- only 2 LE used
- reduced BOS, increased work at heart, increased stress on vb column & LE
- weight of HAT transmitted down to vb column
reduced BOS challenges
- challenging stability
- make some control to maintain balance
COG
- center of gravity
- vertical projection of COM
- dependent on the body position
- in whatever we do, there is a chance that we are shifting our COG fwd, bwd, sideways, or combo
control mechanism of the body
everytime COG is moved, body must maintain its equilibrium/balance, adjustments are made
postural stability/balance
ability to maintain body in equilibrium
t/n: whether body is at rest or in motion (static posture vs dynamic posture)
True/False:
Postural stability entails muscle contractions.
true
t/n: it is a dynamic process when certain muscles (internal forces) will exert their forces to be able to maintain your position
COM
- center of mass
- COM should be maintained OVER BOS for STABILITY (COM/BOS = stability)
t/n: a point at the center of the total body mass represents the concentration of all the mass of the entire body (weighted average of the COM of each body segment)
BOS
- base of support
- support surface
- area of object that is in contact with support surface
Static vs Dynamic Posture
static
- body and its segments are
1) aligned
2) maintained in certain positions
dynamic
- body and its segments are
1) moving
postural control
- postural adjustments body HAS TO MAINTAIN
- muscle activation patterns and segmental movements (that enable us control the body’s segmental linkages in relation to the BOS)
- allow us to properly execute our functional activities without placing too much stress on certain structures
(2) types of postural control
1) reactive = compensatory
2) proactive = anticipatory
reactive/compensatory postural control
reacts to external force displacing body’s COM/external force came intro contact with your bodu
compensatory postural control by which the force is already displaced the body’s COM
e.g. if we try to push someone; and that push came into contact with body = challenges reactive/compensatory postural control
proactive/anticipatory postural control
responds to internally-generated anticipated destabilizing forces
anticipates arrival of external force/force hasn’t come contact into body yet
internally-generated muscle contractions will happen early prior to destabilizing force effect
e.g. riding a roller coaster/fast vehicle, encountering a curve, body adjusts already (bend sideways)
perturbation
sudden nudges/change in conditions that displaces the body away from equilibrium
(2) types of perturbation
1) sensory perturbation
2) mechanical perturbation
sensory perturbation (w/ examples)
alteration of visual input
e.g. covering someone’s eyes when walking in a dark room > challenges visual > challenges posture > sensory perturbation
mechanical perturbation (w/ examples)
displacements affecting COM & BOS/EXTERNAL forces displacing COM out of BOS
e.g. we nudge someone, push someone, ride a train and it suddenly stops
strategies to sensory perturbation
postural strategy
widening BOS (slouch, extend arms, widen legs apart, bend knees)
(3) strategies to mechanical perturbation
1) ankle strategy (prevent too much dorsiflexion)
2) hip strategy (used in stronger force)
3) change-in-support strategies (stepping/grasping)
change-in-support strategy
there is a change in support = your feet/foot STEPS FORWARD
stepping strategy
pushed > step forward > catch COG within that BOS
grasping response
pushed > UE grasp to something > catch body
protective response
(2) head stabilizing strategies
1) Head Stabilization in Space (HSS)
2) Head Stabilization on Trunk (HST)
HSS
- head stabilization in space
- trunk bent sideways (fixed), only head will move contralaterally
t/n: this is to still get proper orientation of the environment
HST
- head stabilization on the trunk
- anticipatory change in head position with the trunk (both head and trunk will adjust)
(2) forces affecting posture
1) internal (muscle/passive tension from static structures)
2) external (inertia/GRF/gravity)
inertial/gravitational forces
- external forces that will affect COG of the body
- why we do postural sway/sway envelope
postural sway/sway envelope
- constant swaying motion of the body in an erect standing posture
- very minimal ANTEROPOSTERIOR / MEDIOLATERAL swaying when STANDING
GRF
- ground reaction forces
- body contacts the ground > ground exerts back same amt. of force
- common when standing/walking
GRF in walking
each time you walk > body exerts DOWNWARD weight > ground exert an equal and opposite reaction (3rd law of newton)
forces on ankle
internal
LOG: anterior to ankle joint/axis
created moment: DF (try to move tibia forward)/flexion
external (counteract external DF moment)
muscle: soleus (create internal PF moment)
t/n: this is to remain state of equilibrium of the body
forces on knee
internal
LOG: anterior to knee joint axis
created moment: knee EXT.
external (counteract hyperEXT.)
structures:
- posterior passive ligaments
- posterior knee capsule (prevent hyperextension caused by femur moving fwd)
muscle: soleus
- pull tibia backwards
- prevent too much movement of tibia fwd
forces on hip & pelvis
internal
LOG: posterior
line of axis: a bit posterior
created moment: pelvic TILTING/hip joint EXT.
external (counteract tilting/ext.)
structures:
- anterior passive structures
- anterior capsule,
- anterior ligaments
- hip flexors (dynamic structures)
forces on lumbar spine
internal
LOG: posterior the segment of lumbar area
created moment: hyperEXT./excessive lumbar lordosis
external (counteract LOG behind)
muscle:
- abdominal muscles
- core muscles
forces on thoracic spine
internal
LOG: anterior
external
muscle: erector spinae (found posterior)
forces on cervical spine
internal
LOG: posterior
external
muscle:
- anterior cervical muscles should contract (prevent posterior pull of cervical spine)
- temporalis (prevent too much opening of mandible)
structures:
- anterior passive structures provide stabilization
(4) postural muscles
1) temporalis
2) trapezius
3) erector spinae
4) soleus
good vs bad posture
good posture
- not much COG displacement
- less muscle acts
- less support from passive structures
bad posture
- excessive COG displacement
- more muscle contraction
- greater stress on passive structures
= fatige muscles > strain injuries
= overly-stretched passive structures > sprain injuries
functional tasks to assess sitting/standing/walking (steady/reactive/proactive state)
sitting
steady: berg 1/sit
reactive: nudge (in any direction)
proactive: berg 2/sit-to-sa=tand
standing
steady: berg 3/stand
reactive: nudge (in any direction)
proactive: berg 6/functional reach test
walking
steady: 10-m walk
reactive: walk w/ perturbation
proactive: dynamic gait index/step over obstacles
(9) factors affecting posture
1) body (height/weight)
2) age (young vs old)
3) gender (male vs female muscle bulk)
4) pregnancy (COG forwarded/challenged stability)
5) occupation and reaction (cross narrow passageways/ballet dancing/single-leg stance)
6) physical conditions (stroke/cerebellar ataxia)
as PT, our goal when considering balance are (5)
1) identify balance issues
2) determine whether static balance/dynamic balance problem
3) know whether problem is d/t reactive/proactive problems
4) know whether muscles are weak
5) know whether certain problems are tight/not flexible
