Transcript Overview of Balance System

Overview Of Balance
Laura Morris, P.T.
University of Pittsburgh Medical Center
SESSION OBJECTIVES
 Describe
the important
terminology used in the study of
balance and mobility
 Identify the multiple systems that
contribute to postural stability
 Describe the major age-related
changes in balance and mobility
Subcomponents of Postural Stability
Flexibility Tone
Joint Range
Temporal Pattern
Morphology
Spatial
Biomechanics
Strength
Detection
of Instability
Motor
Coordination
Multiple Tasking
Sensory
Organization
Motion
Perception
Verticality
Adaptation
Predictive
Central Set
Sensory Strategies
Limits of Stability
Horak, 1997
Systems Contributing to
Control of Balance
 Sensory
peripheral and central
 Motor
including musculoskeletal
 Cognitive/Attention
Important Terminology
Balance
•
A process by which we control the body’s Center
of Mass (COM) with respect to the base of
support (BOS), whether it is stationary or
moving. (standing quietly, leaning in space,
walking)
Mobility
•
The ability to independently and safely move
oneself from one place to another.
(transfers, climbing stairs, walking, running)
Important Terminology
 Anticipatory
Postural Control
• Actions that can be planned in advance
(negotiating obstacles, moving over uneven terrain
in good lighting)
 Reactive
Postural Control
• Actions cannot be planned in advance. Occur
in response to a set of environmental
conditions
(stepping in a hole, being unexpectedly
bumped)
Important Terminology
Stability Limits
• The maximum distance leaned in any
direction without changing the BOS
• Boundaries will vary based on
individual’s abilities, task being
performed, and environmental
constraints.
Postural Control Strategies
Ankle
• Used to control sway when standing
quietly or swaying over small distance in
forward-backward direction
• Requires adequate Range Of Motion
(ROM) and strength in muscles
surrounding ankle joint.
• Sufficient level of sensation in feet and
ankles also important.
Postural Control Strategies
Hip
• Used when surface below feet is narrow
or compliant or, when swaying closer to
stability limits.
• Requires adequate level of strength and
ROM in hip region.
Postural Control Strategies
Step
• Used when the boundaries of stability are
exceeded
• Requires sufficient level of lower body
strength and power, adequate ROM in
hip.
• Adequate level of function in sensory and
motor systems
Age-Related
Changes in the
Older Adult
Commonly Observed
Impairments
Peripheral
Sensory
Central Sensory
Central Motor
Peripheral Motor
Peripheral Sensory
Impairments
 Reduced
Vision
• Acuity
• Contrast sensitivity
• Depth perception
 Effect
on Motor Behavior?
• Ability to accurately perceive and/or
anticipate changes in surface and obstacles
• Navigation in low or changing light
Common Eye Diseases
Courtesy of the National Eye Institute, National Institute of Health
Peripheral Sensory Impairments
Reduced and/or slowed sensation in
touch receptors
• Increase in vibration threshold
• Decreased proprioception
Effect on Motor Behavior?
• Ability to feel quality of contact with
support surface
• Static and changing position of limbs in
space.
Peripheral Sensory Impairments
 Reduced
Vestibular Function
• Loss of hair cells
• Reduction in Vestibulo-ocular reflex (VOR)

Effect on Motor Behavior?
• Head position and/or movement of head in space
• Resolution of sensory conflict
• Balance when vision and somatosensation
absent or distorted.
Central Sensory Impairments
Visually dependent
 Poor integration of sensory inputs
 Distorted perception of true vertical
and/or horizontal
 Slowed processing of sensory
feedback

Central Motor Impairments





Increased planning time
Increased movement times
Strategy selection problems
Increased variation in temporal
sequencing of muscles
Loss of anticipatory control
Effect on Motor Behavior?
 Slower
to initiate and execute
movements, particularly in complex
sensory environments
 Inappropriate choice of movement
strategies
 Slowed gait speed, hesitation during
obstacle negotiation.
 Overall quality of motor coordination
Peripheral Motor
Impairments




Decreased joint range of motion
Decreased strength and power
in lower body muscle groups
Decreased strength in upper
body muscle groups
Decreased muscular endurance
Effect on Motor Behavior?
 Performance
of basic, intermediate,
and advanced activities of daily living
(ADLs).
 Slowed and/or ineffective responses to
sudden loss of balance
 Quality of motor performance
 Increased fatigue
Cognitive Impairment
 Reduction
in Working Memory
 Reduced attentional abilities
Multiple Tasks
Certain sensory environments
 Reduction
in fluid intelligence
Cognitive Impairment
 Fluid
Intelligence:
• Thinking “on the fly” (problem solving)
 Crystallized
Intelligence:
• What you know (vocabulary)
Seated
Moving
Single
Task Demands Multiple
Surface
Type
Cognition
Strength
Environment
Lighting
Standing
Visual
Flow
Individual
Capabilities
ROM
Sensory Loss
Individual Capabilities: Nellie

Strength/Motor control mildly impaired in
both lower extremities

Sensation is within normal limits (WNL)
for her age but vision is impaired

Safety judgment and cognition poor- Not
capable of running down stairs, but
routinely attempts it anyway
Task Demands
 Research
Evidence:
• Attentional demands for postural
stability increase in older adults
• Inability to divide attention between
tasks and postural stability is a
contributing factor to falls (e.g.,
carrying groceries while chatting with
friend)
Task Demands: Judy
 Unable
to climb or descend stairs
without effort and fear
 Experiences
difficulty talking with her
husband as she does the dishes
 No
longer works in the garden
Environmental Constraints
To limit or not to limit, that is the
question…
 Decreased environmental hazards Less
engaging in activities in community  short
term reduced exposure  less falls
 HOWEVER, long term reduced exposure
 deconditioning, less self confidence 
MORE FALLS!

Environmental Constraints:
Billie
 Widowed
one year ago
 Gave dog away as she didn’t feel safe
walking her
 Had to give up volunteer positions
when husband fell ill, has not returned
 Doesn’t feel safe walking outside
anymore, won’t go out at night
Can Age-Related Changes be
reversed?
YES, if:
 Intervention
targets source(s) of
balance-related problems
 Repeatedly exposes older adults to
changing task demands and
environmental constraints