Postural Control Flashcards
What are the two main functional goals of postural control?
postural orientation and equilibrium (stability)
stability and orientation demands will vary with the _________ and the _________
task
environment
what 3 main body s/f contribute to successful postural control?
- sensory process
- motor processes
- cognitive processes
T or F: deficits in one area (sensory, motor, or cognitive processes) can predict dysfunction
false
think individual with diabetic neuropathy can still have decent balance
what is the biomechanical definition of balance
the ability to control the COG over the BOS
________ is the key variable being controlled by the CNS
COM
______- continuously moves around COM to keep COM within BOS
center of pressure (COP)
what are the six requirements for postural control
biomechanical constraints
task dynamics
sensory strategies
orientation in space
movement strategies
cognitive processing
biomechanical constraint includes…
DOF
force production
BOS
COG location
limits of stability
Task dynamics include…
COG location
limits of stability
task demands
sensory strategies include…
sensory integration
sensory reweighting
orientation in space includes…
perception
gravity, surfaces, vision
verticality
movement strategies include…
steady state
anticipatory
reactive
cognitive processing includes…
attention
learning
confidence, fear, self-efficacy, and motivation
an important biomech constraint is the ______ and ______ of the BOS
size and quality
limits of stability def
max distance a person can intentionally displace their COG
what are the limits of stability determined by?
- BOS size
- ROM
- ability to produce force
- ability to detect sensory info
stability limits can be represented as what shape?
cone
do women or men have a higher COG? children or adults?
men
children
what are the 5 points of alignment?
mastoid process
ant. shoulder
hip joints
ant. to knee joint
ant. to ankle joint
why is staying in alignment ideal?
because the body is maintained in equilibrium with least amount of energy expenditure
what are the consequences of poor alignment?
kyphosis
sway back (will affect COP and postural control, if someone pushes you, you’ll have less room to compensate and fall)
what muscles are tonically active in alignment due to COG
erector spinae
ilioposas
glut med
gastroc
soleus
TFL
lesser:
abs
tib ant
bicep femoris
T or F: only COM position influences stability
F - velocity does as well. increased speed, increases displacement
what influences the area of sway tolerated for successful task completion
the task
what is the motor control definition of balance
the coordination of sensorimotor strategies to stabilize the body’s COM during both self-initiated and externally triggered disturbances in postural stability
in a well lit environment with a firm base of support, healthy person’s rely on _________________ (70%), ___________ (20%), and _________ (10%)
somatosensory
vestibular
vision
must ____ and ______ sensory environment in a task specific manner
integrate
weight
if walking on a crazy carpet pattern, what system will you rely less on? SS, vestibular, or vision?
vision
if you are a polar bear walking on slippery ice, what system will you rely less on? SS, vestibular, or vision?
somatosensory
if you are an astronaut floating in space, what system will you rely less on? SS, vestibular, or vision?
vestibular
The ability to ___________ body parts with respect to gravity, the support surface, visual surround and internal references is a critical component of postural control
orient
what elements do you need to have a reference frame for verticality
- somatosensory (support surface)
- vestibular (gravity)
- vision (environment)
orientation deficit
- disruptions in the internal representations of either visual or postural verticality
- automatic postural response not aligned with gravity
- postural instability
what are the 2 vestibular receptors that provide a gravito-inertial frame of reference
semi-circular canals
utricle and saccule
semi-circular canals
head position and movement
utricle and saccule
horizontal and vertical acceleration and deceleration
T or F: the vestibular signals alone can provide a true picture of the gravito-inertial frame of reference
false
what 2 components of vision provide a frame of reference for verticality
- vestibular ocular reflex, smooth pursuit, saccades
- peripheral (ambient) & central (focal) vision
what are some limitations to vision being a reference for verticality
not always necessary or accurate
what are the orientation functions for somatosensory receptors to provide verticality
- position and motion info relative to supporting surface (horizontal)
- relationship of body segments to one another
what are some limitations to using somatosensory receptors as a verticality reference
moving surfaces or non-horizontal surfaces
sensory input from ___________ reduces postural sway
cutaneous receptors
*think surfers
most functional tasks require sensory information to be used in _________ and _________ manner
feedforward
feedback
sensory availability impacts _______ during steady state standing
postural sway
*think Lin’s lab
when do we have more sway during stead state standing?
when somatosensory info is challenged
when only one system is available
When you have a wide BOS, how does postural sway change with eyes open versus closed
it doesn’t change much
for reactive postural control, what type of info is critical
somatosensory
when support surface is rotating, what info is important
vestibular
early in learning, what do you weight more? then with automaticity, what do you weight more?
vision
somatosensory
what are some multiple task dependent synergies for balance control
ankle
hip
combination
change in support (step)
ankle syngergies are for what kind of stability
ant post
hip synergies are for what kind of stability
ant post
m/l
ankle strategy is observed when?
low velocity, small preturbations
firm surface conditions
begins with distal muscle activations
hip strategies are observed when
large, fast preturbations
small BOS
compliant surfaces
proximal muscles activate first
how does the hip recover stability ML?
lateral movement of pelvis
hip abductors and adductors
can muscles be part of multiple synergies
yes
why are synergies important?
allow for activations of synergies in a feedback manner to create context specific adjustments
allows us to simplify movements
more flexibilty
what does anticipatory postural control rely on?
feed forward control
what are two synergies of anticipatory postural control?
preparation (feed forward)
compensation (feedback)
what are some clinical implications for anticipatory postural adjustments
external support
practice
facilitate anticipatory control
increasing stability demands has what effect on attention demands
increases
what are some ways to decrease sway by using vision
focus on visual target while performing a visual task
what are two critical factors that can modify postural control performance
confidence
fear
