Postural Control 1

what are 2 wrong assumptions made about balance control?

• only one or a few “balance centers” in the CNS are responsible for the postural control

• postural control is a set of reflexes that triggered equilibrium responses based on visual, vestibular, or somatosensory processes

is postural control a summation of static reflexes?

no

what is postural control?

a complex skill based on the interaction of dynamic sensorimotor processes

are there brain centers responsible for postural control?

no there are multiple systems that interact to maintain balance

the old assumption that there is one balance system implies what?

that one balance test can measure balance efficacy and that one-dimensional generic balance exercises can improve balance in a group of people with balance disorders and frequent fallers

what is the new view point on balance control?

balance control is complex:

• no one singular balance test can identify balance capability among a diverse group of individuals

• treatment aimed at practicing just one or a few balance tasks can never be optimal for every individual

what are the 2 main functional goals of postural control?

• postural equilibrium

• postural orientation

what is postural equilibrium?

the state in which all forces acting on the body are balanced to:

• maintain a desired body position (static equilibrium/steady state)

• move in a controlled way (dynamic equilibrium)

what is postural orientation?

active control of body alignment and tone with respect to:

• gravity

• surfaces

• visual environment

• internal references

what is the ideal postural alignment?

when the line of gravity falls:

• through the ear lobe

• through the shoulder joint

• midway of the trunk

• through the greater trochanter

• slightly anterior to the knee joint

• slightly anterior to the ankle joint

if what is not maintained, the system will be unbalance?

if the COM is not maintained within the BOS the system will be unbalanced

what are the 6 systems of postural control?

• biomechanical constraints

• cognitive control

• control of dynamics

• limits of stability

• movement strategies

• sensory orientation

what are the biomechanical constraints for postural control?

• base of support

• degrees of freedom

• strength and tone

what are 2 aspects of cognitive control?

attention and learning

what are the 2 aspects of control of dynamics?

• gait

• proactive

what are the 2 aspects of limits of stability?

perception and verticality

what are 2 movement strategies?

anticipatory and reactive

what are 3 aspects of sensory orientation?

sensory integration, sensory reweighting, and somatosensory

with cerebral palsy, do patients typically have a wide or narrow BOS?

narrow BOS especially if they have adductor spasticity

what is the difference between limits of stability when you are upright vs when you are stooped vs when you have PD?

if you are upright, you have more range of limits of stability vs when you are stooped over. if you have parkinsons disease, you have a very small cone of stability where you can move around and not change your base of support

what are limits of stability?

area in which the COM can be safety moved without changing base of support which is shaped like a cone

a healthy elder person will use what strategy to regain balance after moving slightly out of their limits of stability? what about if they have multisensory loss?

ankle strategy; if they have a minor multisensory loss they will use a hip strategy but if they have severe loss, they will immediately go to a stepping strategy

what are the 2 in-place responses for reactive strategies?

ankle and hip strategy

what strategy is used to change base of support?

stepping strategy or reaching

what strategy is used if the person is on a firm surface and the pertubations are slow and small?

ankle strategy

A patient is standing on a firm surface and the surface moves forward underneath them, what direction is the person going to sway, what strategy is being used, and what muscles are being activated?

the person will sway backward; they are using an ankle strategy; distal to proximal muscle activation so tib anterior first, then quads, then the abdominals

A patient is standing on a firm surface and the surface moves backward underneath them, what direction is the person going to sway, what strategy is being used, and what muscles are being activated?

the person will sway forward; they are using an ankle strategy; distal to proximal muscle activation so gastroc first, then hamstrings, then paraspinals

what type of strategy is used when the person is on an unstable surface and the pertubations are fast and large?

a hip strategy

a person is standing on a tilt board and the board tilts down underneath of them. what direction will the person sway, what strategy is being used, and what muscles are being activated?

the person will sway forward; hip strategy; proximal to distal muscle activation so abdominals first, then quads

a patient is standing on a tilt board and the tilt board goes up underneath them. what direction will the patient sway, what strategy is being used, and what muscles are activating?

backward sway; hip strategy; proximal to distal muscle activation so paraspinals and then hamstrings

what strategy is used to prevent a fall and is preferred when the ankle strategy fails to correct movement?

stepping strategy

if someone sways backwards, their posterior muscles fire to maintain them there, but if they sway so far backwards, their anterior muscles have to fire to bring them back forward. this is an example of an anticipatory or reactive balance response?

reactive balance response

if you have a patient do standing arm pulls with their back unsupported, what type of postural adjustment is being made and are the muscles firing before or after biceps? how does this change if you have their back up against a supported surface?

anticipatory postural adjustments; the gastroc and hamstrings are firing before biceps fires; only biceps is firing

anticipatory postural adjustments made prior to voluntary step initiation are ___ in the elderly and even ___ in subjects with parkinson’s disease

smaller; even smaller

what 3 sensory systems interact to maintain balance?

somatosensory, visual, and vestibular

which sensory system is the dominant one in maintaining balance?

somatosensory system

what is the somatosensory system composed of?

• muscle spindles: muscle length and rate of change

• joint receptors/mechanoreceptors

• cutaneous receptors

the ___ system provides the fastest input and reports information from what 2 things?

somatosensory; self-to-surface and limb to limb

the visual system is composed of what?

• eye and visual tracts

• thalamic nuclei

• visual cortex

the visual system reports information from what 2 things? this system is subject to what?

self to surface and head position (keeps visual gaze parallel with the horizon); subject to distortion

the ___ system is not under conscious control and does what 2 things?

vestibular system; assesses movements relative to gravity and resolves inter-sensory system conflicts

the vestibular system is composed of ___ and projects to what?

the cerebellum; brain stem and ear

on a firm surface, there is 70% ___, 20%___, and 10%___

70% somatosensory, 20% vestibular, 10% vision

on an unstable surface, there is 60% ___, 30%___, and 10%___

60% vestibular, 30% vision, and 10% somatosensory

how does a cane help control posture and balance?

it can become a mechanical support or sensory reference

less than ___ grams of touch of one finger helps stabilize posture as well as, or better than vision during stance and treadmill walking

100 grams

if someone is standing on one leg and they start to use a lateral hip strategy where they are leaning over to the side at their hips, what muscle has to fire to prevent them from falling over?

glute med

is standing on one leg anticipatory or reactive balance?

it is anticipatory at first and then it becomes reactive if they lose balance

the control of balancing during gait requires what?

complex control of a moving body COM falling forward and establishing a new BOS to catch the falling COM

what are 2 tests that you can use to measure someone’s cognition while walking ability?

• Walking While Talking Test

• TUG-Cognitive

the more complex the walking challenge is, the more ___ demand it requires

cognitive demand

what does the BEST test look for?

it differentiates balance deficits and looks for what aspect of balance the person is having difficulty with

what are advantages of the BEST test?

• systematic

• comprehensive

• high reliability

• high validity with the ABC

what are problems with the BEST test and how have the modified it?

it has an okay internal consistency and it takes 35 minutes to do it so they eliminated the items that weren’t sensitive and redudantant and made the Mini-BEST which takes 15-20 minutes

the Mini-BEST can help you do what?

guide you into what impairments to test

if you have a patient who displays issues with dynamic balance, what test would be good for evaluating which aspect of balance is their issue?

Mini-BEST test

what items on the Mini-BEST test measure anticipatory balance?

• sit to stand

• rise to toes

• one leg

what items on the Mini-BEST test measure reactive balance?

• step forward

• step backward

• step sideways

what items on the Mini-BEST test measure the sensory system?

• EO stance

• EC on foam

• EO on incline

what items on the Mini-BEST test measure balance during gait?

• change speed

• head turns

• pivot turns

• obstacle

• TUG with cognitive