Lecture 7: Coordination and balance Flashcards
motor control
Motor control: ability of the central nervous system to control or direct the neuromotor system in purposeful movement and postural adjustment by selective allocation of muscle tension across appropriate joint segments
Components of motor control
Normal muscle tone and postural response mechanisms
Selective movements
coordination
Coordination
ability to execute smooth, accurate, controlled movement
Essence is the sequencing, timing, and grading of the activation of multiple muscle groups
Dexterity
Skillful use of the fingers during fine motor tasks
Agility
The ability to rapidly and smoothly initiate, stop, or modify movements while maintaining postural control
balance
Balance: The condition in which all the forces acting on the body are balanced such that the center of mass (COM) is within the stability limits, the boundaries of the base of support (BOS)
centre of mass
Centre of mass: uniquepoint at any given time where the weighted relative position of a distributed mass sums to zero. The midpoint of body mass in erect standing posture; the COM is located at the level of the second sacral segment
base of support
Base of support: Refers to the area beneath a person that includes every point of contact that the person makes with the supporting surface
Sensory systems for postural control
Sensory Systems for Postural Control
Vision
Somatosensory
Vestibular
Focal vision
Focal vision: cognitive/explicit vision; what you are looking at directly .
plays a role in localizing features in the environment in our conscious reaction to visual events
Ambient vision
Ambient vision: sensorimotor/implicit vision; Utilizes the entire visual field to provide information on the localizing features about the environment and to guide movements using largely unconscious awareness.
What is the pathology associated with impaired ambient vision
Optic ataxia: The patient can recognize an object using focal vision but cannot use visual information to accurately guide the hand to the object (impaired ambient vision).
What is the pathology associated with impaired focal vision
Visual agnosia: patient cannot recognize common objects, but can use the ambient visual system to reach and grasp an object or navigate an environment (impaired focal vision)
vestibular system:
- function
- components
- stabilizes gaze during head movements via the vestibulocular reflex (VOR); assist with postural tone and postural muscle activation via the vestibulospinal reflex (VSR)
- semicircular canals and otolith organs
semicircular canals
Semicircular Canals (SCCs): inner ear apparatus that detects angular acceleration. supports person in maintaining upright posture and balance.
otolith organs
Otolith Organs: inner ear organ that detect linear acceleration and orientation of the head with reference to gravity. assists with balance and posture.
What is the primary function of cerebellum
primary function of the cerebellum is regulation of movement, postural control, and muscle tone
rate,range and force of movement
Compares the commands for the intended movement transmitted from the motor cortex with the actual motor performance of the body segment
cerebellar pathology
- Many of these impairments either directly or indirectly influence the patient’s ability to execute accurate, smooth, controlled movements
The motor deficits identified emphasize the crucial influence of the cerebellum on equilibrium, posture, muscle tone, and initiation and force of movement
Basal ganglia 3 main nuclei
caudate nucleus
putamen
globus pallidus
basal ganglia pathology
Patients with lesions of the basal ganglia typically demonstrate several characteristic motor deficits
1. Slowness of movement 2. Involuntary, extraneous movement 3. Alterations in posture and muscle tone
Dorsal Column-Medial Lemniscal function
mediates sensations critical to coordinated movement such as proprioception, kinesthesia, and discriminative touch
Dorsal Column-Medial Lemniscal Pathology
- Lack of joint position sense and awareness of movement, and impaired localized touch sensation
- Gait pattern is usually wide-based and swaying, with uneven step lengths and excessive lateral displacement
- Dysmetria
- Coordination and/or balance problems will be exaggerated when vision is occluded or when the patient’s eyes are closed
Why does proprioception become poorer as a person gets older?
deterioration of the muscle spindles
Why does the vestibulo-ocular reflex and vestibulospinal reflex deteriorate as a person gets older?
deterioration to the calcium carbonate crystals of the otolith
reduction in the number of hair cells in the inner ear
Is there a relationship between changes in strength and ROM with measures of balance?
There is a correlation with strength and ROM with measures of stability
eversion range of motion and plantarflexor strength is related to balance
Is there a relationship between changes in ankle strength and ROM and risk of falls?
What is the difference between non fallers and fallers
- Non fallers have greater ankle flexibility
- Non fallers have less hallux valgus severity
- Non fallers have more sensation in the first joint?
Define: PAT
compare PAT between younger and older adults
proprioceptive acuity thresholds: degrees of joint changes that a person can recognize
There is a larger proprioceptive acuity threshold in older adults
Older adults are less able to reproduce a joint position
Dysdiadochokinesia
An impaired ability to perform rapid alternating movements
This deficit is observed in movements such as rapid alternation between pronation and supination of the forearm
Hypotonia
A decrease in muscle tone
It is believed to be related to the disruption of afferent input from stretch receptors and/or lack of the cerebellum’s efferent influence on the fusimotor system
Dysmetria
An inability to judge the distance or range of a movement
It may be manifested by an overestimation (hypermetria) or an underestimation (hypometria) of the required range needed to reach an object or goal
Dyssynergia
Describes a movement performed in a sequence of component parts rather than as a single, smooth activity
For example, when asked to touch the index finger to the nose, the patient might first flex the elbow, and then adjust the position of the wrist and fingers, further flex the elbow, and finally flex the shoulder
Rebound phenomenon
The loss of the check reflex or check factor, which functions to halt forceful active movements when resistance is eliminated
When application of resistance to an isometric contraction is suddenly removed, the limb will remain in approximately the same position by action of the opposing muscles
Tremor
An involuntary oscillatory movement resulting from contractions of opposing muscles
Intention tremor
An intention tremor occurs during voluntary motion of a limb and tends to increase as the limb nears its intended goal or speed is increased
Postural (static) tremor
Postural (static) tremor may be evident by back-and-forth oscillatory movements of the body while the patient maintains a standing posture
Describe the finger to finger and nose to nose test
objective:
methodology
what a positive sign is
objective: examine cerebellar function
methodology
Patient attempts to touch the index finger of the examiner with an outstretched arm. Requires the subject to fully extend arm and then flex elbow to bring finger back to their own nose.
Fast response is encouraged as the examiner’s arm is moved horizontally
Positive sign:
- Delay in movement initiation
- Terminal tremor – due to alternating contractions of agonist and antagonist
- Dysmetria – inaccurate amplitude, impaired timing of muscle force
Describe the heel to shin test
objective:
methodology
what a positive sign is
objective: assess cerebellar function via coordination
Procedure:
- Patient supine and places heel on the shin of other leg near the knee
- Slide the heel down the shin towards the foot
Positive sign
- Dysmetria – difficulty placing the heel (inaccurate amplitude)
- Dyssynergia - method of getting the heal to shin (flexing the hip and knee in sequence rather than in one synergistic movement
Describe the rebound test
objective:
methodology
what a positive sign is
Procedure:
- Patient performs an isometric contraction of the elbow flexors
- Examiner initially resists force, then releases
Positive
- Patient cannot stop movement once resistance is removed
- Rebound phenomenon – problem with braking of movement
Describe the rapid alternating movements test
objective:
methodology
what a positive sign is
objective: rule out or observe indications of a cerebellar pathology
Procedure
- Patient pats hand on a firm surface
- Patient alternates between palm up and palm down (supination/pronation)
Positive
- Movement is performed slowly and with exaggerated supination and pronation
- Disdiadochokinesia – difficulty performing rapid alternating movements
What are the two movement strategies to control the COM over the BOS?
fixed support strategies:
- ankle strategies and hip strategies
change in support strategies
- stepping strategy
Describe the ankle movement strategy
what
when used
fixed support strategy for small forces that perturb your balance
With forward sway, gastrocnemius is activated first, followed by hamstrings, then paraspinal muscles
With backward sway, the anterior tibialis is activated first, followed by quadriceps, then abdominals
The ankle strategy is a commonly used strategy when sway frequencies are low and disturbances of the COM are small and well within the limits of stability .
Muscles are activated in a distal-to-proximal sequence
Describe the hip movement strategy
what
when used
fixed support strategy used for unanticipated situations where larger forces are applied (ex: person bumps into you while walking, bus turns a corner fast). The hip strategy is typically recruited with faster sway frequencies and larger disturbances of the COM or when the support surface is small
With forward sway abdominals are activated first, followed by quadriceps
With backward sway, paraspinal muscles are activated first, followed by hamstrings. Hip strategies provide primary control for mediolateral stability
Hip muscles (abductors and adductors) are activated to control lateral sway
It has a proximal pattern of muscle activation before distal activation
Describe the stepping strategy
what
when used
Realigns the BOS under the COM by using rapid steps or hops in the direction of the displacing force, for example, forward or backward steps
In instances of lateral destabilization, the individual takes a side step or a cross step to bring the BOS back under the COM
The stepping strategies are typically recruited in response to fast, large postural perturbations when ankle and hip strategies are not adequate to recover balance
What are the common strategies for balance perturbations when sitting?
grasping (ex: edge of seat)
or hooking the lower extremity around the legs of furniture
What are the common strategies for balance perturbations when standing?
ankle/hip strategies or stepping strategies. depends on the weakness and limited ROM in ankle or hips
Describe anticipatory postural control.
How to test it?
Anticipatory postural control, the ability to activate postural adjustments in advance of destabilizing voluntary movements, should be examined
For example, the therapist asks the patient while standing or sitting to raise both arms overhead or catch a weighted ball
Dual task control
how to test?
Dual task control: This is the ability to perform a secondary task (motor or cognitive) while maintaining standing or seated control
For example, while standing the patient is asked to count backward from 100 by 7 (simultaneous verbal-cognitive task) or pour water into a glass (secondary motor task)
Describe the romberg test
objective
methodology
+ or negative findings
Objective: assess dorsal column medial leminiscus tract for lesions by assessing person’s proprioception and vestibular function
methodology: During the test, the patient is instructed to stand with feet together, eyes open (EO) unaided for 20 to 30 seconds
If the patient demonstrates significant sway or instability with EO, the test is over. The patient is then asked to stand with eyes closed (EC)
Test is positive if sway is significantly worse or person loses balance with eyes closed compared to eyes open.
Describe the functional reach test
objective
methodology
describe the relationship between functional reach test scores and risk of falls?
objective: measure the limits of stability of individuals while reaching forward in a standing position
Functional reach is the maximal distance one can reach forward beyond arm’s length while maintaining a fixed base of support in the standing position
no relationship between risk of falling
Describe the Berg balance test
objective:
methodology
14-item scale that quantitatively assesses balance and risk for falls
objective: designed to quantitatively assess balance in older adults
It can also be used with patients post-stroke
methodology: Items are scored from 0 to 4, with a score of 0 representing an inability to complete the task and a score of 4 representing independent item completion
The greater the score, the better the balance.
Components:
- Sit to stand
- standing unsupported
- standing to sitting
- standing unsupported with eyes closed
- turning 360 degrees
- standing on one leg
Is the berg balance score a reliable outcome measure?
Can the BBS be used to predict falls in older adults?
high interrater reliability; high inter rater reliability
The evidence to support the use of BBS to predict falls is insufficient
