Postural Control In Neuromuscular Disorders Flashcards
What is the relationship between CoM and BoS?
fundamental to maintaining balance and stability in both static and dynamic situations
For a person to maintain balance, the CoM must remain within the BoS
If the CoM shifts outside the BoS, the person will likely lose balance and fall unless corrective actions are taken
in dynamic activities, such as walking or running, the CoM moves relative to the BoS, but stability is maintained through adjustments in posture, gait, and movements
to stay balanced, the body makes postural adjustments to ensure that the CoM remains within the BoS. These adjustments involve shifting weight, altering body posture, or adjusting the BoS (e.g., moving feet or changing stance width)
Center of Mass (CoM):
The point where the mass of an object or body is concentrated. For the human body, it is typically located just anterior to the sacrum in the pelvis
*S2
It is where the gravitational forces act and is central to the body’s balance
Base of Support (BoS):
The area between and including the points of contact with the supporting surface
For a standing person, this is the area defined by the feet. A larger BoS generally provides greater stability
Neuromuscular Control:
The nervous system continuously monitors the CoM relative to the BoS and makes rapid adjustments through muscle activation and coordination to maintain balance.
Feedback Mechanisms:
Sensory feedback from visual, vestibular, and proprioceptive systems helps the body detect shifts in the CoM and initiate corrective actions to maintain stability.
Balance Strategies:
ankle
hip
stepping
Ankle Strategy:
Involves small adjustments using the ankles to maintain CoM within the BoS, useful for minor perturbations.
Hip Strategy:
Involves larger movements at the hips to maintain balance when the CoM is significantly displaced.
Stepping Strategy:
Involves taking a step to enlarge the BoS when the CoM has moved too far outside the BoS to maintain stability.
Center of Pressure (CoP):
The point of application of the resultant ground reaction force acting on the body
It is the average location of the vertical forces exerted by the ground through the base of support (BoS)
It represents the point where the pressure is effectively concentrated during standing or dynamic activities
CoM vs. CoP:
CoM: Represents the point where the body’s mass is concentrated and where gravity acts.
CoP: Represents where the ground reaction forces are applied. In static conditions, the CoP needs to be within the BoS to maintain balance.
The CoP shifts in response to movements and adjustments to keep the CoM within the BoS.
Measuring CoP:
Force Plates: CoP is often measured using force plates, which capture the distribution of forces exerted by the feet and calculate the location of the CoP. This measurement is valuable in assessing balance and postural control.
In clinical settings, CoP measurements can help evaluate balance disorders, the effectiveness of interventions, and the risk of falls.
Resources required for postural stability and orientation:
biomechanical constraints
cognitive processing
control of dynamics
orientation in space
sensory strategies
movement strategies
biomechanical constraints:
degrees of freedom = number of independent ways a system (like a joint or a body segment) can move
strength = ability of muscles to produce force, essential for generating movement and maintaining posture
limits of stability = boundaries within which the body can maintain balance without changing its base of support (like stepping or reaching)
> distance a person can lean or shift their center of mass while maintaining balance
cognitive processing:
attention = Effective postural control requires cognitive resources to monitor and adjust posture. Attention to body position and environmental changes is necessary for balance maintenance
learning = The ability to recall and apply learned strategies for maintaining balance and orientation is essential, especially in novel or challenging situation
control of dynamics:
gait = Gait is a dynamic process that involves the coordination of muscles, joints, and sensory feedback to maintain balance and propel the body forward
proactive = body’s ability to anticipate and prepare for changes in movement based on previous experience or environmental cues
> body uses sensory input (vision, proprioception) to predict obstacles or changes in terrain, and adjusts movements accordingly before encountering them
orientation in space:
perception = involves integrating sensory input from multiple systems, including vision, the vestibular system (inner ear), and proprioception (sensory feedback from muscles and joints)
gravity, surfaces, vision = estibular system, specifically the otolith organs in the inner ear, detects changes in head position relative to gravity
> Proprioceptive feedback from the body and contact with surfaces (such as the ground) informs the brain about how the body interacts with the environment
verticality = perception of uprightness and alignment with respect to gravity
sensory strategies:
sensory integration = brain’s ability to combine information from different sensory systems—vision, vestibular (inner ear), and somatosensory (proprioception and touch)—to form a coherent understanding of the body’s position and movement in space
sensory reweighting = body’s ability to adjust the relative importance of different sensory inputs based on the situation or the reliability of the available information
> when walking in the dark, visual input becomes unreliable, so the brain “reweights” the sensory inputs, relying more on proprioception and vestibular information
movement strategies:
reactive = automatic responses that occur after a disturbance or loss of balance
> ankle, hip, stepping
anticipatory = pre-programmed movements that occur before a voluntary action or an expected disturbance, allowing the body to prepare for potential challenges to balance
> important for smooth, coordinated movement and preventing falls during tasks that require planning, like reaching for something on a high shel
voluntary = conscious, intentional movements aimed at accomplishing a specific task, such as walking, reaching, or changing posture
> controlled by higher brain centers and are goal-directed, allowing flexibility and adaptability in complex environments
Postural control- involves multiple systems = postural control system
1) Sensory Systems:
-vision’
-vestibular
-proprioception
-exteroception
2) Sensory Integration and Weighting
3) Brain Areas Involved in Postural Control
- Pre-frontal Cortex
- Primary Motor Cortex
- Frontal and Pre-motor Cortex
- Cerebellum
- Brainstem
4) Pathways
- Dorsal
- Ventral
5) Motor response = body generates a motor response (e.g., adjusting posture or movement) to maintain stability
Ventral pathway =
“WHAT” Pathway
involved in object identification and recognition, helping us understand what we are looking at
processes information related to the form, color, and details of objects
starts in the occipital lobe (where visual information first arrives) and travels to the temporal lobe, an area associated with recognition of objects, faces, and scenes
It answers questions like:
“What is this object?”
“Is this familiar to me?”
“What are the object’s characteristics (color, texture, shape)?”
Dorsal pathway =
“WHERE” Pathway
involved in spatial awareness, helping us determine where objects are in relation to ourselves and guiding our movements
starts in the occipital lobe and moves towards the parietal lobe, an area involved in processing spatial location and motion
It answers questions like:
“Where is this object located?”
“Is it moving? In what direction?”
“How can I interact with it (e.g., reaching, grasping)?”
Dorsal Pathway to Posterior Parietal Cortex:
Supports spatial awareness and attention, allowing the body to understand “where” it is in space
Ventral Pathway to Inferotemporal Cortex:
Involved in object recognition and identification, processing “what” is in the environment
Vision:
Provides visual input about the environment, helping the body understand its position relative to objects and surroundings
Vestibular System:
Located in the inner ear, it helps detect changes in head position, motion, and orientation relative to gravity
Proprioception:
Involves the sensory feedback from muscles, joints, and tendons, giving the body awareness of its position in space
Exteroception:
Provides information from external sensory receptors in the skin, contributing to the awareness of environmental contact (such as pressure or texture from the ground)
Pre-frontal Cortex:
Involved in decision-making and planning movements
Primary Motor Cortex:
Responsible for the execution of voluntary motor movements
Frontal and Pre-motor Cortex:
Involved in the planning and initiation of movement
Cerebellum:
Coordinates timing and precision of movements and fine-tunes motor responses
Brainstem:
Regulates automatic postural responses and integrates sensory and motor signals
Sensory Signals:
Sources: Visual, vestibular, auditory, proprioception, touch, and visceral systems provide sensory feedback to the brain about the body’s position and movement relative to its environment.
Proprioceptive and Skin Afferents: These signals convey information from the body’s joints, muscles, and skin, helping the central nervous system understand its spatial orientation and posture.
Basal Ganglia:
Central to motor control, the basal ganglia play a major role in initiating and regulating voluntary movements. It processes sensory input and sends signals to the cerebral cortex and other brain areas to refine motor actions. Dopamine from the basal ganglia affects movement regulation.
Cerebral Cortex:
The cognitive reference is represented by the cerebral cortex, which governs voluntary movements and cognitive processes involved in postural adjustments. The cortex integrates sensory feedback and decision-making processes, which are essential for initiating and modifying movements.
Thalamus:
Serves as a relay station, transmitting sensory signals (e.g., proprioceptive feedback) to the cortex for processing and integrating them with motor commands.
Limbic System:
The emotional reference is represented by the limbic system, which influences emotional motor behavior. Emotional states can directly affect posture and movement, integrating emotional responses with motor control.
Automatic Processes:
Midbrain, Pons, Medulla: These areas are involved in automatic postural adjustments and reflexive movements. The cerebellum fine-tunes movements and coordinates balance.
Spinal Cord & Central Pattern Generators (CPGs): The spinal cord houses CPGs, which control rhythmic movements such as walking. These generators help maintain automatic locomotion without conscious effort, regulated by sensory feedback and brain input.
Spinal Locomotor Network:
Involved in automatic and rhythmic movements, the spinal locomotor network is essential for walking and maintaining posture, allowing for dynamic adjustments based on proprioceptive and sensory feedback.
Motor Outputs:
Automatic Movements: Controlled by subcortical structures (brainstem, cerebellum, spinal cord), these involve reflexive and rhythmic activities, like maintaining posture while standing or walking.
Voluntary Movements: Controlled by the cerebral cortex and basal ganglia, voluntary actions are goal-directed and consciously initiated, such as deciding to change posture or walking toward an object.
Postural control in Stroke
83% of pts. 2-4 wks post stroke -> balance disability
Motor control impairments (caused by reduction in # and firing rate of motor units): slow movements, weakness, fatigue, incoordination, decreased force production, co-contractions
Reduction in the Number and Firing Rate of Motor Units:
Damage to the brain affects the recruitment and activation of motor units, which are responsible for muscle contraction.
Slow Movements (Bradykinesia):
Movements become slower due to a reduced ability to activate muscles rapidly. This can limit the speed and efficiency of postural adjustments.
Weakness (Paresis):
Muscle weakness is a hallmark of stroke, particularly on one side of the body (hemiparesis), and is associated with reduced muscle strength and endurance, contributing to postural instability.
Fatigue:
Stroke patients often experience physical and mental fatigue, which further impairs their ability to maintain posture, particularly during prolonged activities.
Incoordination:
Loss of motor coordination results in jerky or uncoordinated movements, impairing the ability to execute smooth postural adjustments and movements.
Decreased Force Production:
Muscles affected by the stroke produce less force, making it difficult to perform actions that require strength, such as standing, walking, or reaching.
Co-contractions:
In some cases, there is excessive co-activation of antagonist muscles, resulting in stiff and inefficient movements, which hinder smooth postural adjustments.
Postural Control Challenges Post-Stroke:
Asymmetry in Weight Distribution
Delayed Postural Responses
Impaired Anticipatory Postural Adjustments (APAs)
Sensory Deficits
Poor Coordination of Balance Strategies
Asymmetry in Weight Distribution:
Stroke patients often exhibit uneven weight-bearing, with a tendency to shift weight towards the non-affected side. This asymmetry affects balance and stability.
Delayed Postural Responses:
Normally, the body reacts quickly to maintain balance when perturbed, but stroke patients often exhibit delayed and weaker postural responses, increasing the risk of falls.
Impaired Anticipatory Postural Adjustments (APAs):
Stroke can affect the ability to prepare the body for upcoming movements, such as shifting weight before stepping. This impairment can lead to instability and falls during voluntary actions.
Sensory Deficits:
Stroke may impair proprioception and other sensory feedback mechanisms, making it difficult for patients to detect changes in body position and adjust accordingly.
Poor Coordination of Balance Strategies:
Stroke affects the ability to utilize balance strategies effectively, such as ankle, hip, and stepping strategies that help maintain upright posture in response to perturbations.
what leads to the decrease in speed?
decrease number of FT MUs and increase atrophy of type 2 fibers -> slower muscle contractile properties
what leads to the decrease in strength?
decrease supraspinal drive and increase recurrent inhibition -> slower MU firing rates
what leads to the decrease in precision?
increase co-contraction and decrease coordination -> reduced net force
fast twitch =
type 2 fibers
slow twitch =
type 1 fibers
EMG recordings during a single squat in a subject 1-month post-stroke (right) and a healthy age- and sex-matched control (left)
Delayed activation in terms of anticipatory of key muscles in healthy adults - delayed timing and reduced activation of other muscles
Stroke: quite different acceleration pattern - anterior tip fires before the squat - to set up firing before you go - non paretic leg overshoots - paretic doesn’t go
Deceleration phase -less amplitude and delayed firing
Healthy: pretty symmetrical acceleration pattern
Deceleration phase - both quads and hamstrings fire at similar time
Postural control in Stroke
3 global impairments in balance:
sensation (to detect or anticipate postural disturbance)
neural processing (to select appropriate feedback/feedforward postural control)
effective motor output
sensation:
Impairment: Stroke can affect sensory pathways, leading to reduced ability to detect or anticipate postural disturbances
This can include deficits in proprioception (awareness of body position), vestibular function (sense of spatial orientation), and somatosensation (sense of touch and pressure)
Difficulty in perceiving shifts in body position or external forces can impair the ability to make timely adjustments to maintain balance
Neural Processing:
Impairment: Stroke can disrupt the brain’s ability to process sensory information and select appropriate feedback or feedforward mechanisms for postural control
This includes issues with integrating sensory inputs and generating appropriate motor responses
Ineffective neural processing can result in poor decision-making regarding postural adjustments, leading to unstable or inappropriate responses to balance challenges
Effective Motor Output:
Impairment: Motor output can be compromised due to weakened or impaired muscle activation and coordination
This affects the ability to execute and adjust motor responses required for maintaining balance
Reduced strength, coordination, and control over movement can lead to difficulties in maintaining posture and responding to perturbations, increasing the risk of falls
Impairment to the timing, magnitude and sequencing of muscle activation:
Timing of Muscle Activation: disrupt the neural pathways responsible for coordinating the precise timing of muscle contractions
> can result in delayed or premature muscle activation during movements
Magnitude of Muscle Activation: can affect the ability to generate sufficient force in the muscles
> due to weakened muscle strength or reduced motor control
Sequencing of Muscle Activation: involves the correct order of muscle activation for coordinated movements
> disrupt this sequence = leading to improper muscle activation patterns
Delayed muscle activation can lead to:
difficulty in responding quickly to balance disturbances or changes in posture
Premature activation might cause instability or excessive muscle tension, both of which can affect overall balance and movement efficiency
Inadequate muscle activation magnitude can result in:
insufficient support for maintaining posture or performing movements
can make it challenging to maintain balance, especially during dynamic tasks or when faced with unexpected perturbations
Incorrect sequencing can lead to:
inefficient or uncoordinated movements
might cause a person to rely excessively on certain muscle groups while neglecting others, leading to poor balance and increased risk of falls
Rehabilitation Strategies:
timing
Use exercises that focus on improving the timing of muscle activation
This might include tasks that require rapid adjustments to changing conditions or feedback-based training to help the patient react more promptly to balance challenges.
Rehabilitation Strategies:
magnitude
Implement resistance training and functional exercises to increase muscle strength and improve the ability to generate adequate force
Tailor exercises to address specific muscle groups that are weakened or underperforming.
Rehabilitation Strategies:
sequencing
Incorporate coordination and motor control exercises that emphasize proper sequencing of muscle activation
Use tasks that mimic functional movements and gradually increase complexity to enhance sequencing accuracy.
Postural control in PD
As Parkinson’s disease advances, there is a progressive loss of postural stability, which contributes to an increased risk of falls = motor and sensory system impairments affecting the ability to maintain and adjust posture
Gait abnormalities such as shuffling, reduced arm swing, and difficulty initiating or stopping movement are common = gait dysfunction
Postural instability less responsive to drug therapy
Up to 68% falls in later stages of ds
Lack of balance reaction, flexed posture, decreased trunk rotation, difficulty executing simultaneous movements/sequential movements
Forward-Flexed Posture in Parkinson’s Disease:
shifts the body’s center of gravity forward
shift makes it more challenging to maintain balance, particularly during dynamic movements or when responding to external perturbations
Basal Ganglia =
controlling the flexibility of postural tone
scaling up the magnitude of postural movements = regulating how much muscle activation is needed to maintain or correct posture
selecting postural strategies for environmental context
automatizing postural responses and gait = more deliberate, effortful, and less fluid movements
Progression of PD
mobility -> bradykinesia and rigidity
kinesthesia problems -> freezing
decline in executive function -> inflexible set
non-motor symptoms:
cognitive processing
- attention
-learning
rigidity:
biomechanical constraints:
- degrees of freedom
- strength
- limits of stability
bradykinesia:
control of dynamics
- gait
- proactive
movement strategies
- reactive
- anticipatory
- voluntary
sensory strategies
- sensory integration
- sensory reweighting
proprioception deficits:
control of dynamics
- gait
- proactive
Healthy adults stand up on force plate and PD pts:
Diff direction perturbations
Solid black line - healthy adults = cone of stability - big
Stooped posture - decreased stability margin especially with backward stability area
PD - especially small stability margin - especially backward
PD patients on force plate - look at COP trajectory and postural sway (resting)
a good way of sway - instability front to back
> On DBS - it reduces postural sway
> On L DOPA - NOT ALWAYS - but in general doesn’t help postural control
> On DBS and LDOPA - decreases some but still isn’t great
Postural control in mTBI
Balance disorders- one of the most common symptom
23-81% report dizziness
Postural instability due to dysfunction in sensory integration
Deficits in cognition -> attention affects postural control
In mild traumatic brain injury (mTBI), also known as a concussion, postural control can be significantly affected
balance issues such as dizziness, unsteadiness, and difficulty maintaining equilibrium = result from disruptions in the vestibular, visual, or proprioceptive systems
ability to process sensory information from the environment and the body = lead to difficulties in integrating visual, vestibular, and proprioceptive inputs necessary for maintaining balance
ability to coordinate and execute postural adjustments may be compromised
may experience slower reaction times, affecting their ability to respond quickly to sudden changes in posture or balance
concussion:
traumatic brain injury that changes the way your brain functions
brain is made up of soft tissue and is protected by blood and spinal fluid - when skull is jolted too fast or is impacted by something - brain shifts and hits against the skull
can lead to bruising and swelling of brain, tearing of blood vessels and injury to nerves, causing concussion
most concussions are mild and can be treated with appropriate care - but left untreated, it can be deadly
Reaction time affects postural stability and righting reactions =
Reaction time affects postural stability and righting reactions
*those with TBI or concussion = slower reaction time
delayed response to sudden shifts or disturbances in their posture
challenging to adapt to changing conditions quickly, leading to instability
Righting reactions = automatic adjustments to maintain an upright position, can be delayed
> impacting the individual’s ability to recover from perturbations and maintain an upright posture
Postural control in MS
Due to extensive damage to CNS
Demyelination -> sensorimotor cortex, basal ganglia, cerebellum, spinal pathways
Motor learning preserved in early phase of MS -> capacity dependent on severity
While motor learning—especially the ability to adapt and acquire new motor skills—may remain preserved in the early stages of MS, the capacity for motor recovery and learning is highly dependent on the severity of CNS damage
MS disease progresses =
postural control can become increasingly impaired, potentially leading to issues such as unsteady gait, increased risk of falls, and difficulty in performing coordinated movements
Capacity to improve postural control depends on severity of disease
Critical deficit: slowed spinal SS conduction ->
delayed postural latencies and increased postural sway
Postural sway - good with eyes open - not closed
*with MS
*exacerbated swaying with eyes closed
Not switching to the lead - still lagging
*not kicking in optimally
*demyelination - nerves cant carry info fast
Patients often demonstrate better stability with their eyes open, but closing the eyes exacerbates swaying because they rely more heavily on the remaining sensory systems (like vision) to compensate for impaired proprioception and vestibular input
delayed response, or the inability to “switch to the lead,” occurs because demyelinated nerves cannot carry information quickly enough. As a result, the body’s postural adjustments lag, leading to less optimal balance control
Postural Control in SCI
Aberrant (or absent) synapse formation leads to inappropriate muscle recruitment and poor coordination
Changes in excitability of spinal locomotor networks render some synapses hyperexcitable and some hypoexcitable
Chronic SCI -> progressive deterioration of muscle properties diminishes the ability to generate movements
No consistent superspinal drive
Lots of muscle changes
*Further diminishes the ability
of muscles to generate moment
study by Jorgensen et al., published in Spinal Cord, focuses on assessing unsupported sitting in patients with spinal cord injury (SCI):
assessment of unsupported sitting in SCI patients was reliable and valid when modified from stroke-specific scales
individuals with incomplete spinal cord injury (SCI) were found to have better unsupported sitting balance compared to those with complete SCI
Higher scores = better sitting balance
*lower injuries = more core muscle control to be able to sit
ASIA A L1 - good balance
T10 ASIA C
Could look very diff.
Lots of variability in incomplete ASIA cases
Greater total sway and postural sway than those without SCI
Vestibular system roles:
Perception of body position and self-motion = helps sense movement and orientation in space
Orientation of trunk to vertical = ensures that the body is aligned with gravity
Controls COM (postural reactions) = triggers postural reactions to maintain stability
Stabilize head in space = keeps the head stable in space, especially during movement, aiding in clear vision and balance
Acute onset of vestibular symptoms = can be huge
often indicate sudden dysfunction in the vestibular system
severe dizziness, vertigo, imbalance, nausea, or difficulty stabilizing vision can lead to major disruptions in daily activities and postural control
may be related to various causes, such as vestibular neuritis, labyrinthitis, or even more serious conditions like strokes
postural control in patients with bilateral vestibular failure (BVF)
BVF patients exhibit significant postural instability, especially when deprived of visual or proprioceptive feedback
Postural sway is increased in BVF patients, especially with eyes closed - Visual feedback helps compensate for vestibular loss, making sway comparable to healthy controls when eyes are open
When proprioceptive feedback is reduced (e.g., standing on foam), BVF patients show greater instability, even with visual input
Vestibular input loss destabilizes BVF patients, especially during head movements, but cognitive tasks didn’t significantly worsen their balance compared to controls
Balance Evaluation: Outcome tools: Stroke*
Berg Balance Scale: MDC = 2.5-8.1
Dynamic Gait Index: MDC = 2.6-4
Functional Reach Test: MDC = 2.3-6.79
Timed “Up & Go”: MDC = 2.9s
*Highly recommended
Other Outcome tools: Stroke
6 min walk test
10 meter walk test
Fugl-Meyer (LE)
Functional Independence Measure
Goal Attainment Scale
Motor Activity Log
Orpington Prognostic Scale
Stroke Impact Scale
Stroke Rehabilitation Assessment of Movement—Limb Subscales (STREAM)
Balance Evaluation: Outcome tools: PD*
Berg Balance Scale: MDC = 5
Dynamic Gait Index: MDC = 2.9
Functional Gait Assessment: MDC = 4
MiniBesTest: MDC = 5.52
Timed “Up & Go”: MDC = 3.5-11s
*Highly recommended
Other Outcome tools: PD
6 min walk test
10 meter walk test
MDS-UPDRS revision
Mini Mental Status Exam
Montreal Cognitive Assessment
PDQ-39
PDQ-8
Timed Sit to Stand, 5 times
Balance Evaluation: Outcome tools: mTBI
High Level Mobility Assessment (HiMAT)- MDC = 4 points or decrease of 2 points
*Good for concussion - looks at balance - more high functioning people with TBI
*No highly recommended
Other Outcome tools: mTBI
mTBI (concussion) EDGE currently under development at ANPT
TBI EDGE* available
Coma Recovery Scale- Revised
Moss Attention Rating Scale
“Recommended” balance measures include: 6 min walk test, 10 meter walk test, BBS, Community Balance and Mobility Scale
Balance Evaluation: Outcome tools: MS*
Berg Balance Scale- MDC =not available
Dizziness Handicap Inventory- MDC= 22.50
TUG w/Cognitive & Manual- MDC =not available (dual tasking hard with this population)
*Highly recommended
Other Outcome tools: MS
12-Item MS Walking scale
6 min walk test
9-hole peg test
MS Functional Composite
MS Impact Scale-29
MS- QoL 54
Timed 25 ft walk
Balance Evaluation: Outcome tools: SCI*
TUG- MDC= 10.8 seconds
*Highly recommended
Other Outcome tools: SCI
6 min walk test
10 meter walk test
ASIA Impairment Scale
Hand-Held Myometry
Walking Index for SCI II
Numeric Pain Rating Scale
WHO QoL- BREF
Balance Evaluation: Outcome tools: Vestibular Disorders*
Dynamic Gait Index- MDC= 3.2 points
Dizziness Handicap Inventory- MDC= 17.18
Functional Gait Assessment- MDC=- 6points
*Highly recommended
Other Outcome tools: Vestibular Disorders
New call for EDGE task force for revisions
Dix-Hallpike
Postural Control- Interventions Balance Rehabilitation
Study to measure pre and post intervention stuff
Rate of falls improved after intervention - in intervention group
*activating muscles Sooners - reduce rate of falls
*didn’t change in control group
Latency kicked in sooner to the task after the training = what we want - training anticipatory postural adjustments
Healthy older adults:
good evidence
dose-response relationships of ”balance training” parameters
training period of 11-12 wks
frequency of 3x/week
31-45 minutes per session
36-40 total # of sessions
Variety of training modalities (commonly multimodal exercise-based balance training)
Chronic stroke:
good evidence
balance/wt. shifting and gait training effective
balance/wt. shifting and gait training effective
improve proprioceptive feedback, which is crucial for maintaining balance and coordinating movements
Gait training helps improve walking speed, stride length, and overall gait mechanics
Parkinson’s Disease:
good evidence
exercise interventions probably reduce rate of falls
mod intensity PRE
2-3x/wk over 8-10 wks
variety of exercise types, including resistance training, balance exercises, and aerobic activities, have been shown to improve balance and mobility, thereby reducing fall risk
Multiple Sclerosis:
medium evidence
balance interventions have a medium effect on outcomes
high intensity* & task-specific interventions are associated with better outcomes
interventions include balance training exercises, stability and coordination drills, and exercises targeting specific balance deficits
high-intensity interventions often result in greater improvements in strength and endurance compared to moderate or low-intensity exercises
Vestibular disorders:
medium evidence
moderate evidence for improved postural stability following vestibular rehab exercises
mTBI:
weak evidence
weak evidence for vestibular rehab exercises, subthreshold aerobic exercise
Concussion - weak evidence for subthreshold aerobic exercise in terms of improving BALANCE only
*not a lot of RCT on balance training specificily
Incomplete SCI:
weak evidence
weak evidence for BWST (+ stimulation – FES or tDCS), small scale studies on VR-based balance training show promise
Incomplete SCI - weak evidence
-FCS to muscle or tDCS to brain
*Reminder: Key Components of Postural Control
1) biomechanical constraints
2) stability limits/verticality
3) anticipatory postural adjustments
4) postural responses
5) sensory orientation
6) stability in gait
biomechanical issue example:
ankle strength/ROM
Weakness in the muscles surrounding the ankle, particularly the dorsiflexors (muscles that lift the foot) and plantarflexors (muscles that point the toes)
poor control of foot movement, increased risk of tripping or falling, difficulty with activities like walking uphill or climbing stairs, and general instability
stability limits example:
reaching
When reaching, the body’s center of mass shifts towards the direction of the reach. This shift can challenge balance and stability.
area within which the body’s weight is supported by the contact with the ground (e.g., feet). As one reaches, the base of support effectively becomes narrower, increasing the risk of losing balance
Reaching further requires greater control and stability
anticipatory postural adjustments example:
planned change of position
Before the person begins to stand, muscles are activated to stabilize the body and prepare for the shift in weight. This includes activating the muscles of the trunk (e.g., abdominal muscles and erector spinae) and lower extremities (e.g., quadriceps and gluteals
pre-activation helps to counteract the forward shift of the center of mass that occurs when moving from a seated to a standing position
person may lean slightly forward or shift their body weight towards their feet before initiating the standing motion. This movement helps to align the center of mass over the base of support (the feet) to prepare for the lifting action
Reactive responses example:
unplanned response - step
person perceives the loss of balance, often through sensory feedback from their feet and proprioceptors, indicating that they are tilting or shifting unexpectedly
Early detection of the disturbance allows for a faster and more effective reactive response
person quickly initiates a step to regain balance. This step is typically a rapid and unplanned movement designed to adjust the base of support and realign the center of mass over the feet
By stepping in the direction of the disturbance, the individual expands their base of support and shifts their center of mass back within a stable zone
By stepping in the direction of the disturbance, the individual expands their base of support and shifts their center of mass back within a stable zone
sensory orientation example: impact of vision/vestibular system
In a busy environment, visual input helps the person navigate around obstacles and maintain awareness of their surroundings
vestibular system works to stabilize the visual field by adjusting head and eye movements. In dynamic environments, it helps maintain balance by sensing changes in head position and motion
If a person with impaired vision (e.g., due to cataracts or blurred vision) tries to walk down the street, they may struggle to detect moving objects or judge distances correctly, increasing the risk of collisions or falls
gait example: change gait speed or direction or cognitive load
Walking at an increased pace requires the person to take quicker steps and increase stride frequency = Faster gait speed challenges balance control and requires greater coordination and muscle strength
Walking at a reduced pace involves longer steps and a slower cadence = Slower gait speed can improve stability and reduce the risk of falls but might be associated with reduced momentum and difficulty in navigating certain obstacles
