Contributing factors to motor control
Task Factors
-stability= req when sitting or standing static
-mobility= req when moving BoS
-Task may be manipulated to increase demand
Eg: lifting load, accuracy for task, task certainty and complexity, body orientation
Environmental factors
- Regulatory features= influence mvmt so must conform to those features eg uneven surfaces
- Non-regulatory features= may affect mvmt performance but mvmt does not have to conform to them eg. Background noise
Individual Factors
- Perception= discernment of sensory info+ high level interpretation
- Cognition= attention, planning, problem solving, motivation, engagement, emotion
- Action= how certain activity is accomplished
Define postural control
Control of body’s position for orientation and balance
- Orientation=controlling relationship between body segments, task, environment
- Balance= controlling CoM in relation to BoS
Describe Stationary BoS
Maintained control of orientation and balance when not moving
SUSTAIN= hold a posture eg sit or stand still
MAINTAIN= maintain control over stationary BoS when performing a movement eg Reaching
RETAIN= retain control when responding to perturbation
eg. push or sneeze
Describe Changing BoS
Maintained control of orientation and balance when
PROJECT= project body up and down from position eg hop or jump
PROPEL= propel body towards new position eg stand up, sit down
PROTECT= protect body in response to external perturbation eg. take a step to prevent falling
Strategies used in Postural Control
Neuromuscular Synergies Adaptive Mechanism Anticipatory Mechanisms Individual Sensory system Sensory strategies Musculoskeletal components internal representations
Describe NM Synergies
-set number of strategies used by CNS= prevent loss of balance by correcting displacement of COM+ to keep it within BoS in event unpredictable perturbation
E.g Ankle, hip and stepping strategies
-Combo of strategies used
Describe Adaptive mechanism
- use feedback from sensory and motor system –> more variable corrective component than NM synergies
- Used after both unexpected and expected perturbations
- Development of direction specific patterns + fine tuning –> req to develop head control, sitting, standing
Describe Anticipatory Mechanism
-FF system of PC- pre tuning sensory and motor systems prior to mvmt
-based on predictions made by the CNS
-Diagram:
Anticipatory reaction= presents in FF manner, either before or simultaneously to prime mover
Adaptive reaction= presents after prime move, correction to disturbance
Time separating anticip+ reactionary at 50ms after onset of prime mover activity–> this is time req for sensory feedback + second motor output to be generated
-Development of anticipatory mech
Describe Individual sensory system
Tactile, visual, somatosensory, vestibular
-provides info to CNS of body’s position and mvmt
Describe Sensory strategies
-How info is organised + interpreted from individual sensory system contributes to PC
-Tactile= orients body to stim
Vestib= central reference for other systems
Prop= relative position of body parts, orient to support surface, joint pos sense, muscle length
VIsion= motivates to move, orient to visual surrounds by 6months
Describe development of sensors
Utero
-Tactile by 3wks
Newborn
-Tactile= primary sense after birth
-Vision= preterm infant can follow but not focus until term. Drives exploratory behaviour + mvmt
-Prop= present at/soon after birth
-Vestibular= drives head response initially (3-6 months), then vision takes over as system matures
2-3 years
-vision dominates, prop + vestibular contribute
4-6 years
- very variable
- tactile largely mature by 4y
7-8+ years
- prop from feet
- vision- less important unless leaning new skill
- vestib mature by 6y
Describe Musculoskeletal components
- PC affected by growth, body alignment, muscle and postural tone, muscle strength, joint ROM
- Growth= changes in shape and height- head vs body size, limb length, trunk length, growth of organs, soft tissue (CoG infants=T12, adults L5)
- Body alignment= flexor position initially, 3-6 months dev Cx curve, 8months dev Lx curve
Describe internal representations
Provide postural frame of reference–> related to sensory input to develop maps or internal rep of body schema
Deficits in PC shown in children with Neurological disorders
CP Developmental co-ord disorder Spina Bifida Down Syndrome Autism Premature birth Sensorineural Hearing loss
6 elements of postural control
Sensory orientaiton Anticipatory postural adjustments Reactive postural responses Stability limits/verticality Stability in gait Biomechanical constraints
Tests for Biomechanical constraints
MSK- components
- BoS
- COM alignment
- Ankle strength with ROM
- Hip/Trunk lateral strength
- Sit on floor+ stand up
Tests for Reactive Postural Responses
NM synergies, adaptive mech
- in place response forward + bid
- compensatory stepping correction- fwd, bad, lat
- attempts to elicit responses of ankle+ hip strategies
Test for Anticipatory postural adj
Anticipatory mech
- sit to stand
- rise to toes
- Stand on one leg
- alternate stair touch
- standing arm raise
Tests for Sensory orientation
Sensory strategies, individual sensory system
- Sensory integration for balance ( modified CTSIB)
- Incline - EC
Tests for stability limits/verticality
Internal represent
- sitting verticality and lateral lean (L and R)
- Functional reach forward
- Functional reach lateral
Tests for stability in gait
All
- Gait on level surface
- Change in gait speed
- Walk with horizontal head turns
- Walk with pivot turns
- step over obstacles
- Timed up and go test
- Timed up and go w/dual task
Vertical head righting
Ability: orient head to gravity when trunk is displaced away from vertical orientation no loss of head position when body moves underneath
- Uses sensory perception of movement (away from vertical), optical head righting, vestibular head righting
Typical Performance = Normal absence in newborns emerges at 3mo remains throughout life
Atypical= partial/full loss of head orientation, head movement causes increase or decrease in muscle tone
Horizontal head righting
Ability: orient head to gravity when trunk is displaced away from vertical orientation no loss of head position when body moves underneath
Typical performance = normal absence in newborns emerges 4-5mo remains throughout life
Atypical= loss of head orientation, abnormal tone
Horizontal head right/landau
Ability: orient head, trunk, LL to gravity when positioned in prone suspension via Cx, trunk, hip and knee ext, PF in prone
Typical = normal absence in newborns emerges 4-5mo w/ Cx ext rest occurs at 6mo and remains through life Atypical = partial/delayed response, abnormal tone
