MIDTERM #2 Flashcards
Injuries to each of these somatosensory pathways will result in?
in different sensory impairments
Somatosensory cortex damage will result in sensory deficits on what side of the body?
the opposite side of the body
Training can facilitate cortical reorganization
Ex if you can sense touch you may not sense temperature and may burn yourself without knowing
Visual System: When the dorsal stream is affected what happens?
Motion sense deficits (“where”)
Altered perceptions related to the movement and spatial relationships between body and objects
Visual System: When the ventral stream is affected what happens?
Object identification deficits (“what”)
Altered perceptions related to specific aspects of an object
Visual System: When the ventral stream is affected what happens?
Object identification deficits (“what”)
Altered perceptions related to specific aspects of an object
Visual field deficits will depend on the location of what?
the lesion (follow the paths)
Damage in different areas affects different things
Dorsal – perceiving
Ventral - identification
What is visual agnosia?
The patient had great difficulty in identifying objects, even though his vision was otherwise normal, and he could describe the features of what he saw.
What is Hemianopsia?
Hemianopsia refers to damage to the visual pathways such that visual information from the retinas do not reach the cerebrum
What is Hemispatial Neglect?
Hemispatial neglect refers to damage in processing areas – often posterior parietal cortex – such that sensory input on one side is ignored
What is the dorsal stream related to perceptions/movement?
Dorsal stream - perceptions related to the movement and spatial relationships between body and objects
What is the dorsal stream related to perceptions/movement?
Dorsal stream - perceptions related to the movement and spatial relationships between body and objects
What is the Vestibulo-spinal tracts?
postural stability of neck, trunk, limbs
What is the Vestibulo-ocular tracts?
stabilization of eyes during head movement
Vestibular system lesions can lead to?
Postural control/balance deficits
Poor gaze stabilization
Vertigo/dizziness
What is the Vestibulo-ocular reflex (VOR)?
Generates eye movement in opposite direction from head movement
Stabilizes image on retina during movement
What is perception?
integration and conscious awareness of sensory information
What is coordination?
ability to sort, retrieve, and manipulate information
e.g., damage in posterior parietal cortex (sensory integration) and prefrontal cortex (cognitive function) can complicate the motor learning process
What is postural control?
ability to control the body’s position in space for the purposes of orientation and stability
How does postural control require interaction between the nervous system and musculoskeletal system?
Motor components
Sensory/perceptual components
Cognitive components
Musculoskeletal components
ROM, strength, flexibility
Additions to the venn diagram?
Previously broke tasks up into those involving stability, mobility, and manipulation
Postural tasks are stability and orientation tasks
Types of postural control?
Steady state control
Reactive control (reactive postural adjustments, RPAs)
Anticipatory control (Anticipatory postural adjustments, APAs)
What is Steady state control?
Maintain postural stability in predicatble, non-changing conditions
What is Reactive control (reactive postural adjustments, RPAs)?
Modification of motor/sensory systems to meet changing task and environmental demands
Strategies selected to respond to sensory feedback associated with external perturbations (e.g., support surface moves)
What is Anticipatory control (Anticipatory postural adjustments, APAs)?
“Pre-tuning” of motor/sensory systems based on previous experience
Strategies selected to anticipate a potentially destabilizing voluntary movement (e.g., lifting an object)
What is Anticipatory control (Anticipatory postural adjustments, APAs)?
“Pre-tuning” of motor/sensory systems based on previous experience
Strategies selected to anticipate a potentially destabilizing voluntary movement (e.g., lifting an object)
What is postural orientation?
Ability to maintain an appropriate relationship between body segments and between the body and environment
A key component of many functional tasks is the ability to maintain a vertical body orientation
What is postural stability (balance)?
Ability to control the centre of mass (COM) relative to the support
Postural orientation requires input from?
Somatosensory system – body and support surface info, body segment info
Visual system – body and environment info
Vestibular system – position of the head relative to gravity
How is postural stability achieved (balance)?
Postural stability is achieved when the line of gravity (LOG) falls within the base of support (BOS)
The larger an object’s base of support (BOS), the greater the stability
Example of how different tasks requires different levels of postural orientation and stability?
Stay stable on bridge vs keeping feet orientated to stay in bounds
How os the centre of pressure (COP) measured?
Centre of pressure (COP) often measured in motor control research using force plates
Allows quantification of “postural sway” during steady state control
The point of force application between an object and its support surface is the?
Centre of pressure
The area bounded by the outermost points of contact between an object and its support surface is the?
Base of support
The point around which an object’s mass is equally distributed?
Centre of mass
The point around which an object’s mass is equally distributed?
Centre of mass
The downward vertical projections (i.e., toward the earth) of the Centre of Mass is the?
Line of gravity
What are the stability limits?
the boundaries within which a person is able to maintain stability without changing their base of support (e.g., taking a step)
The stability limits are dependant on what many factors?
Size of BOS
Position, velocity of COM
Musculoskeletal system – range of motion, strength, flexibility
Cognitive system – fear of falling, perception of safety
Environment – support surface, distractions
What are kinetic measures?
examine relationships between forces acting on the body and the changes in motion or equilibrium that they produce
Centre of pressure (COP) provides a kinetic measure
What are Kinematic measures?
examine an object’s motion without consideration of the forces involved (i.e., displacement, acceleration, velocity)
Consider body segment movement relative to each other and environment
What are Electromyography measures?
When an action potential travels down a muscle fibre, an electromagnetic field is created around the fibre that can be detected by an electrode near the field
What is surface EMG?
electrodes placed on the skin Intramuscular EMG – wires or needles inserted into a muscle
The EMG signal is the what?
waveform resulting from the summation of all the detected action potentials
Electromyography measures can be used to estimate what?
Which muscles are active and to what extent
The timing and coordination of muscle contractions
Neuromuscular fatigue
EMG studies have greatly improved understanding of?
anticipatory postural adjustments (APAs)
Figure shows activation of a number of trunk/postural muscles prior to activation of arm muscles when people asked to lift arm as quickly as possible
Example in class anti-gravity answers (steady state, anticipatory, reactive, postural orientation, postural stability, COM, LOG, BOS, COP)?
Steady state – holding the position
Anticipatory – getting into the position
Reactive – minimal reactive control
Postural orientation is key for striking the po9se
Postural stability is key for holding it - STRENGTH
COM – point where objects mass is equally distributed
LOG – vertical line from COM to floor
BOS – outermost points of contact between object and surface
In this example, the COM is forward relative to the feet, making the LOG way outside of the BOS, suggesting state of high instability
If measured, where would the COP be located?
COP would be between feet (remember, it is the of force application)
Visual agnosia is often related to damage along the _______ stream of visual processing?
ventral
The centre of pressure is a ________ measure?
Kinetic
There are several factors that contribute to stability during upright stance which are?
Alignment
Muscle Tone
Postural Tone
What is alignment?
ideal posture maintains equilibrium with minimal energy
What is muscle tone?
resistance to passive stretch through contributions from neural (i.e., stretch reflex) and non-neural (i.e., tissue stiffness) components
What is postural tone?
tonic activity in anti-gravity muscles that maintain alignment in a narrowly confined vertical posture (influenced by somatosensory, visual, vestibular systems)
What strategies are part of the anteroposterior stability?
Ankle strategy
Hip strategy
Stepping strategy
What is the ankle strategy for forward body sway?
Forward body sway -> ankle strategy involving posterior leg muscles (gastrocs, hamstrings, erector spinae)
What is the ankle strategy for backward body sway?
Backward body sway -> ankle strategy involving anterior leg muscles (TA, quads, abdominal muscles)
About ankle strategy?
Muscle activity ~90-100 ms after perturbation onset
Order of muscle activation is distal to proximal
Leg muscles produce ankle torque to slow body motion, thigh and trunk maintain neutral alignment at knee and hip
Ankle strategy experiment?
series of stretch reflexes vs muscle synergy?
Experiment
Platform is “translated” (forward/backward) -> stretches leg, thigh, hip muscles (body lean)
Platform is “rotated” (toes up/down only) stretch of leg muscles only (no body lean)
Hypotheses
If series of stretch reflexes, responses should be different
If a muscle synergy, responses should be the same
What is the hip strategy for backward body sway?
Backward body sway -> hip strategy involving posterior muscles of the thigh and trunk (i.e., hamstrings, erector spinae)
What is the hip strategy for forward body sway?
Forward body sway -> hip strategy involving anterior muscles of the thigh and trunk (i.e., quads, abdominal muscles)
What is the hip strategy for forward body sway?
Forward body sway -> hip strategy involving anterior muscles of the thigh and trunk (i.e., quads, abdominal muscles)
About hip strategy?
Muscle activity ~90-100 ms after perturbation onset
Order of muscle activation is proximal to distal
Causes rapid translation of the pelvic girdle (COM) towards BOS
What is the stepping strategy?
Forward or backward motions causes a change in BOS (e.g., reach, step)
Used when “in-place” strategies (e.g., ankle, hip) are insufficient to maintain stability
What are the stepping strategy considerations?
Stepping strategies often follow attempts to maintain stability using in-place strategies
Stepping strategies can occur even when the LOG stays within the BOS
How would you go about selecting a strategy?
Early work suggested that the ankle and hip strategies were distinct entities
Small/slow perturbations = ankle strategy
Large/fast perturbation = hip strategy
How would you go about selecting a strategy?
Early work suggested that the ankle and hip strategies were distinct entities
Small/slow perturbations = ankle strategy
Large/fast perturbation = hip strategy
Recent research indicates that feedback is used continuously to determine what?
to determine the relative emphasis on each strategy based on task and environmental conditions
What is Low perturbation velocity?
mostly ankle strategy
What is Medium perturbation velocity?
more ankle strategy, a bit of hip strategy
What is Medium perturbation velocity?
more ankle strategy, a bit of hip strategy
What is High perturbation velocity?
both ankle and hip strategy
Nervous system “____” the strategies used based on demands?
scales
What are muscle synergies?
A muscle may belong to muscle synergies
A muscle makes unique contributions to each of its synergies
**The total activation of a muscle depends on the number of its synergies that are active, and how much it is contributing to each of them
What is the current model of multidirectional postural control?
Humans have 5-6 control strategies (including ankle, hip, stepping)
Each synergy activates its set of muscles in a fixed amount
Combined effects of these synergies produces force profile between foot and support surface
Sensory input (i.e., somatosensory, visual, vestibular) provides continuous feedback regarding body position in space to inform activation of synergies to maintain stability
What is an application of Reactive (feedback) control?
Postural control system uses feedforward (anticipatory) and feedback (reactive) control
Neuropathology could affect one of these control methods more than the other
What is an application of Reactive (feedback) control?
Postural control system uses feedforward (anticipatory) and feedback (reactive) control
Neuropathology could affect one of these control methods more than the other
Ability to continuously modulate which synergies are active based on feedback is key, how can you incorporate this into activities?
Training programs should incorporate activities that require continual modulation of postural strategies
E.g., firm surface (ankle strategy), soft surface (hip strategy), multi-directional perturbations
What is an application of Anticipatory (feedforward) control?
Postural muscles activate in anticipation of destablizing voluntary movements
Same synergies involved in feedback postural control (e.g., ankle and hip strategies) involved with feedforward postural control
See slide 18 control of posture
What is the visual system?
Provides information about the position and motion of the body relative to other objects and the environment
Provides a reference to horizontally-aligned and vertically-aligned objects
What is the vestibular system?
Provides information about linear and rotational accelerations of the head
Provides information about the position of the head relative to gravity
What is the somatosensory system?
Provides information about the:
Position of the body segments relative to each other (e.g., joint receptors, muscle spindles)
Characteristics of the support surface (e.g., material, transitions)
Position of the body relative to the support surface (reference to horizontal)
Somatosensory input about a support surface that is moving or not horizontal provides an inaccurate reference to the horizontal
What does the visual system have difficulties with?
The visual system has difficulty distinguishing between object motions (i.e., exocentric) and self-motion (i.e., egocentric)
What does the vestibular system have difficulties with?
The vestibular system has difficulty distinguishing between movements of the head in isolation from movements of the head and body together (e.g., head nod vs body lean)
Evidence of visual system contributions?
Postural sway increases when eyes are closed vs open
If placed in a room where the walls oscillate back and forth but the floor stays stationary, postural sway will increase to match the oscillations
Evidence of vestibular system contributions?
Merry-go-round
Evidence of somatosensory system contributions?
Postural sway increases when somatosensory input from the lower limbs is reduced (e.g., peripheral neuropathy)
Vibration of certain muscles (e.g., ankle, neck) and the dorsal/plantar surfaces of the feet cause a direction-specific increase in postural sway
E.g., dorsal surface vibration = ↑ anterior sway; plantar surface vibration = ↑ posterior sway
Components of feedback control?
Latency
Magnitude
What is latency of postural control?
Latency of postural control responses – somatosensory perturbations <visual perturbations
What is magnitude of postural control?
Magnitude of postural control responses – somatosensory perturbations > vestibular perturbations
What happens when separate perturbations occur very close together?
Latency of response to second perturbation is delayed
Magnitude of response to second perturbation is decreased
What happens when separate perturbations occur very close together?
Latency of response to second perturbation is delayed
Magnitude of response to second perturbation is decreased
Processing different types and multiple sources of sensory input is?
Demanding
All three sensory systems contribute to postural control, how is this possible?
Early response to perturbation relies heavily on somatosensory input
Response to rapid perturbations relies heavily on somatosensory input
Later response to perturbation relies heavily on visual and vestibular input
Integration from these systems is complex and involves shared supraspinal and spinal pathways
What is Multisensory integration in postural control?
Each sensory system provides unique information/frame of reference
None of these systems is absolutely necessary, but postural control is compromised when:
There is a loss of information from at least one system
There is inaccurate information from at lease one system
What is the Sensory Organization Test” (SOT)?
Measure body-sway under 6 conditions
1-3 – somatosensory info accurate, visual info available, absent, or inaccurate
4-6 – somatosensory info inaccurate, visual info either available, absent, inaccurate
What is the inaccurate visual information?
head in box that moves as the person sways, giving illusion that they are still
What is the inaccurate somatosensory information?
– support surface rotates as person sways, giving somatosensory illusion that they are still
Postural sway lower when?
when somatosensory info is accurate vs inaccurate
when visual info is absent vs inaccurate
Postural sway highest when?
when only vestibular system provides accurate info
Slide 6 postural control pt 2
What is the Sensory Weighting Hypothesis?
To optimize postural control, the CNS modifies relative dependence on each system based on their relative accuracy
Relative dependence on each system varies based on individual factors (e.g., age) as well as task and environmental factors (e.g., low light)
Dial up dependence on other systems when one system is failing (for example, cant see so you go for somato and vest)
What is the Sensory Weighting Hypothesis?
To optimize postural control, the CNS modifies relative dependence on each system based on their relative accuracy
Relative dependence on each system varies based on individual factors (e.g., age) as well as task and environmental factors (e.g., low light)
Dial up dependence on other systems when one system is failing (for example, cant see so you go for somato and vest)
Application of “Sensory Organization Test” (SOT)?
Use of appropriate postural control strategies compromised when info from one or more systems becomes unavailable or inaccurate
Postural control training could incorporate activities that promote reliance on alternative systems or retraining of disrupted system
Ability to organize and weight sensory info based on relative accuracy is key
Need to incorporate activities that require continual modulation of sensory weightings
Moving from one sense to another, constantly changing dependence
Cognitive system includes what components?
Attention
Selective
Divided
What is attention?
ability to focus on a specific stimulus without being distracted
What is selective attention?
focus in the presence of distracting stimuli
What is divided attention?
respond simultaneously to multiple tasks
Dual-task paradigms commonly used to test what?
attentional demands of postural control
Maintaining balance and postural control takes lots of attention – you may not realize it in certain situations
What is postural control and attentional resources?
Attentional demands associated with postural control increase with postural challenge (e.g., narrow stance, wide stance; stand, sit)
Attentional demands of postural control higher in older individuals and those with CNS pathology
What are factors that contribute to aging? Include intrinsic and extrinsic factors.
Aging is a natural process, part of development
Involves physiological adaptation that leads to a change in function
Intrinsic factors: structural changes at the cellular level (e.g., DNA/genetics)
Extrinsic (environmental) factors: e.g., lifestyle; exposure to pathogens, toxins, etc.
What are factors that contribute to aging? Include intrinsic and extrinsic factors.
Aging is a natural process, part of development
Involves physiological adaptation that leads to a change in function
Intrinsic factors: structural changes at the cellular level (e.g., DNA/genetics)
Extrinsic (environmental) factors: e.g., lifestyle; exposure to pathogens, toxins, etc.
What is Active aging (WHO)?
The process of optimizing opportunities for health, participation and security in order to enhance quality of life as people age. It applies to both individuals and population groups.
What are implications for rehab in older adults?
Optimal lifestyle factors during aging promote maintenance of optimal function
Rehab strategies can be effective in returning function towards an optimal state if nervous system decline is observed in a healthy older adult
Nervous system decline may be characterized by an overall decline in function, or be limited to specific neural structures/functions
What does heterogeneity of age mean?
Wide variety of physical function among people of the same chronological age
A “continuum of physical function” has been proposed to categorize older adults based on their physical function capabilities rather than their age
What are Basic activities of daily living (BADLs)?
self-care tasks (e.g., bathing, dressing, feeding)
What are Instrumented activities of daily living (IADLs)?
allow an individual to live independently in a community (e.g., housework, shopping, preparing meals)
The Public Health Agency of Canada defines a fall as?
“a sudden, unintentional change in position resulting in an individual landing at a lower level such as an object, the floor, or the ground, with or without injury”
What is the epidemiology of falls?
~1/3 of older adults fall at least once each year
Falls are the leading cause of injury-related hospitalization for older adults
Falls are a significant factor in the morbidity (e.g., disability) and mortality of older adults
The risk of falling increases linearly as?
as the number of risk factors increases
Aging and falls Individual/Biological factors?
muscle weakness (particularly in the lower limbs), postural instability, gait instability, visual deficits, cognitive impairments, use of certain medications (e.g., sedatives)
Aging and falls task factors?
use of an assistive device, speed, stairs
Aging and falls environment factors?
throw rugs, slippery surfaces, inadequate lighting
What Age-related changes are involved in what Motor Systems?
Musculoskeletal System
Steady-state Postural Control
Reactive Postural Control
Anticipatory Postural Control
What are the age related changes in the Musculoskeletal System?
Muscle cells decrease in size/number with age, leading to changes in functional capacity
Decreased muscle strength (i.e., force produced during a maximum contraction)
Decreased muscle endurance (i.e., ability to contract continuously at submaximal levels)
Muscle atrophy and reduced muscle strength in the lower limbs are strong independent predictors of?
severe functional impairments in older adults
Task-specific functional disability occurs when?
muscle strength falls below the threshold required to perform a task
Task-specific functional disability occurs when?
muscle strength falls below the threshold required to perform a task
Bone density gradually decreases with age, leading to?
an increased risk of fractures
Range of motion decreases in many joints with age
Ex. ankle/hip strategies are impacted with less range of motion
Spinal flexibility and ankle flexibility decrease by as much as what %?
50% (age 85) (both are important for postural alignment and postural control)
What are the age related changes in the Steady-state postural control System?
Compared to younger adults, older adults generally demonstrate:
Larger magnitudes and velocities of spontaneous postural sway
Smaller functional stability limits (i.e., COP displacement during maximal voluntary sway)
Need to consider different postural sway conditions (eyes closed, tandem stance, dual-task)
Lower postural sway not always better, how?
e.g., Parkinson’s Disease rigidity may result in less sway under normal conditions; may need to provide more challenge to reveal impairments
What are the age related changes in the reactive postural control System?
Compared to younger adults, older adults generally demonstrate:
Slower onset latencies of the postural control muscles
Lower activity (amplitudes) of the postural control muscles
Longer time for COP to stabilize
Increased co-activation of agonist (postural control) and antagonist muscles
Increased use of hip strategy
What are the age related changes in the reactive postural control System?
Compared to younger adults, older adults generally demonstrate:
Slower onset latencies of the postural control muscles
Lower activity (amplitudes) of the postural control muscles
Longer time for COP to stabilize
Increased co-activation of agonist (postural control) and antagonist muscles
Increased use of hip strategy
The use of stepping strategies that involve multiple steps is associated with an increased risk of?
falls in older adults
Other common reactive postural patterns with aging include side stepping rather than cross-over, limb collision on side step, arm movements
Anticipatory postural control strategies may also be compromised in what population?
older adults
(i.e., contraction of the postural control muscles is delayed and occurs almost simultaneously with the prime mover muscles)
Compared to young adults, older adults generally demonstrate ____________ onset latencies and _________ muscle activity during reactive postural control?
Blank 1: slower; Blank 2: lower
What are the age related changes in the somatosensory System?
The number and acuity of sensory receptors decrease with age (e.g., proprioception, pressure)
The number of sensory nerves innervating these receptors decreases with age (e.g. peripheral neuropathy)
Age-related somatosensory deficits lead to increased reliance on visual/vestibular inputs
What does the feet have to do with Age-related changes – Sensory/Perceptual Systems?
Plantar sensitivity decreases with age (higher activation thresholds of receptors)
Cutaneous reflex amplitude decreases with age
These losses are associated with greater COP postural sway
What age related changes does the visual system go through?
The eye undergoes many age-related structural changes – e.g., lens (cataracts), retina (macular degeneration), optic nerve (glaucoma)
These structural changes lead to functional visual deficits – e.g., decreased visual acuity, decreased visual contrast sensitivity, visual field loss, increased visual threshold
In a room in which the walls oscillate back and forth while the floor remains stationary, older adults demonstrate?
Increased postural sway relative to controls
Increased activity (amplitudes) in the postural control muscles relative to controls
These effects are greater in unstable older adults – they rely more on the visual info, even when it is inaccurate
The number of vestibular receptor cells and vestibular nuclei cells decrease with?
age
Vestibular dysfunction leads to?
Reduced ability to resolve conflicts between the somatosensory and visual systems (e.g., moving room)
Increased frequency and intensity of dizziness (i.e., lightheadedness/unsteadiness) and/or vertigo (i.e., false perception of motion) during particular movements
Ex. as you get older, swings don’t feel the same
What are multi-sensory deficits?
Sensory organization test (SOT) allows measurement of body sway (COP movement) under 6 conditions that vary the availability and accuracy of visual and somatosensory information
Somatosensory organization test (SOT) allows measurement of body sway (COP movement) under 6 conditions that vary the availability and accuracy of visual and somatosensory information
What are multi-sensory deficits?
Sensory organization test (SOT) allows measurement of body sway (COP movement) under 6 conditions that vary the availability and accuracy of visual and somatosensory information
Somatosensory organization test (SOT) allows measurement of body sway (COP movement) under 6 conditions that vary the availability and accuracy of visual and somatosensory information
When at least two sensory modalities were providing accurate information (Cond 1-4) what happens?
older adults demonstrated comparable postural sway compared to younger adults *
When only one sensory modality was providing accurate information (Cond 5-6) what happens?
older adults demonstrated significantly more postural sway than younger adults **
When somatosensory information is inaccurate (Cond 4-6) what happens?
older adults with a history of falls lost balance more often than younger adults or older adults without a history of falls *
When visual information is inaccurate (Cond 3 & 6) what happens?
older adults with AND without a history of falls lost balance more often than younger adults **
What is the most dominant sense?
Vision is the dominant sense and becomes more and more dominant as we age.
Postural control responses are likely to be severely compromised for older adults in environments in which?
visual and/or somatosensory information are either inaccurate or unavailable (e.g., low light conditions, soft compliant flooring)
What is attention and dual tasking?
Attentional capacity decreases with age
Maintaining postural stability requires more attention with increasing age
Older adults use more attentional resources to?
maintain posture
Older adults show reduced postural muscle activity during?
dual-task
Multitasking in activity divides attention away from postural stability
Evidence for improving postural control in elderly?
Balance exercises: significantly decreases postural sway
Resistance exercises: no significant effect
Weak evidence that some types of exercise (gait, balance, co-ordination and functional tasks; strengthening exercise; 3D exercise and multiple exercise types) are moderately effective, immediately post intervention, in improving clinical balance outcomes in older people
Either no or insufficient evidence to draw any conclusions for general physical activity (walking or cycling) and exercise involving computerised balance programmes or vibration plates
Evidence for improving postural control in elderly?
Balance exercises: significantly decreases postural sway
Resistance exercises: no significant effect
Weak evidence that some types of exercise (gait, balance, co-ordination and functional tasks; strengthening exercise; 3D exercise and multiple exercise types) are moderately effective, immediately post intervention, in improving clinical balance outcomes in older people
Either no or insufficient evidence to draw any conclusions for general physical activity (walking or cycling) and exercise involving computerised balance programmes or vibration plates
Neurologic pathology and falls statistics?
~1/3 of older adults experience a fall each year
~1/2 of individuals who have a stroke fall at least once per year post-stroke
~1/2 of individuals with Parkinson’s disease fall at least once per year
~1/2 of individuals with multiple sclerosis fall at least once per year
For all of these conditions, balance impairments are considered to be a significant independent risk factor for falls
Steady state and abnormal postural control?
Over time, hypertonia (spasticity, rigidity) can lead to stiffness, muscle shortening, bone and joint deformities
What is alignment?
relationship between body segments, and between the body and the base of support
What is parkinson’s disease?
stooped posture (flexor rigidity, loss of spinal flexibility)
What is cerebral palsy?
reduced joint ROM (spasticity, contractures)
What is a stroke?
weight-bearing asymmetry (paresis, disuse atrophy)
What are the consequences of altered alignment?
Increased effort required to support the body against gravity
Ideal posture allows maintenance of equilibrium with minimal energy expenditure
Affects the characteristics of spontaneous postural sway
*Also affects the movement patterns available for controlling stability (reactive and anticipatory postural control)
What is a Weight-bearing asymmetry (stroke)?
Increased weight-bearing on the non-involved limb
Asymmetry tends to improve over time but seldom resolves completely
Asymmetric weight-bearing is a compensatory strategy
May be effective with severe impairment and not advisable to change in some patients
What many factors contribute to the asymmetry?
Paresis, asymmetric tone, somatosensory deficits
Functional stability limit can be measured as what?
the amount of COP displacement that occurs during a maximal voluntary sway effort
People with neurologic conditions commonly show what?
reduced stability limits
Functional stability limits test interaction between motor system, sensory system, and cognitive system
Compensatory body weight shift therapy is a strategy used to correct?
Asymmetric weight bearing
A functional stability test typically evaluates which type of postural control?
Steady state
What is response coordination?
Individuals with stroke demonstrate delayed onset and reduced amplitude of muscle activity in the lower limb on the hemiparetic side
Individuals with cerebral palsy show (on spastic side)?
Delayed onset of muscle activity
Reduced amplitude of muscle activity
Altered patterns of activity
Ankle-foot orthoses (AFOs) are often prescribed to provide support what?
provide support to a weakened lower limb (e.g., hemiparesis) or to control ankle position and movement (e.g., spasticity)
Although AFOs provide mechanical support, they also affect postural response strategies (e.g., reduced ankle strategy use, reduced frequency of distal to proximal order of activation)
Individuals with multiple sclerosis show?
delayed onset of leg muscle activity compared to controls
Demyelination leads to slower nerve conduction times
Co-activation of proximal muscles during postural control is common in?
is common in many neurological conditions (e.g., stroke, cerebral palsy, Parkinson’s)
May be the result of a compensation strategy or loss of inhibition to antagonists
What are the consequences of response coordination?
Delayed onset of distal muscles associated with reduced ankle torque and large shifts of the COP during perturbation recovery
Delayed onset of proximal muscles associated with increased hip/knee motion during perturbation recovery (recall that proximal muscles maintain neutral alignment at these joints)
Co-activation is an inefficient and ineffective balance recovery strategy (more energy, less adaptability)
What is response scaling?
People with neurological conditions commonly demonstrate an impaired ability to adapt the postural control response amplitude to perturbation amplitude (e.g., smaller vs larger or slower vs faster perturbations)
What is Cerebellar degeneration?
excessive postural responses
What is cerebral palsy?
inability to scale response based on perturbation difficulty
What is cerebral palsy?
inability to scale response based on perturbation difficulty
Why is co-activation of agonist-antagonist muscle pairs considered a poor balance recovery strategy?
A. It requires a lot of energy
B. It limits response adaptability
C. It is compensatory
D. Both A and B
D. Both A and B
Many neurological conditions impact anticipatory postural control strategies, for example, cerebral palsy, how?
Cerebral palsy (arm push/pull)
Non-involved side: postural muscle activity -> prime mover activity (normal); Involved side: prime mover activity -> postural muscle activity (abnormal)
Stroke (rapid arm movement)
Non-involved side: postural muscle activity -> prime mover activity (normal); Involved side: prime mover activity + postural muscle activity simultaneous (abnormal)
Many neurological conditions impact anticipatory postural control strategies, for example, cerebral palsy, how?
Cerebral palsy (arm push/pull)
Non-involved side: postural muscle activity -> prime mover activity (normal); Involved side: prime mover activity -> postural muscle activity (abnormal)
Stroke (rapid arm movement)
Non-involved side: postural muscle activity -> prime mover activity (normal); Involved side: prime mover activity + postural muscle activity simultaneous (abnormal)
