Week 7 Flashcards
What is balance?
Dynamic process by which
the body’s position is maintained in equilibrium
When is balance greatest?
Greatest when COM, or COG, is maintained over BOS
What is the center of mass?
The unique point where
the weighted relative position of the distributed mass sums to zero, or the point where if a force is applied causes it to move in direction of force without rotation
What is the center of gravity?
Vertical projection of the center of mass to the ground
Where is the CoG in the anatomical position?
2nd sacral vertebra
What is momentum?
Product of mass times velocity
What is the BoS?
Perimeter of the contact area between the body and its support surface
What alter the BOS and changes a personal postural stability?
Foot placement
What happens for a person not to fall?
If a person maintains their COG within the limits of the BOS, (aka limits of stability), they do not fall
What is the limit of stability?
The sway boundaries in
which an individual can maintain equilibrium without change his or her BOS
The limit of boundaries constant constantly change depending on what?
The task, individuals’s biomechanics, and aspects of
the environment
What is ground reaction force (GRF)?
Force exerted by the ground on a body in contact with it
What is center of pressure?
Location of the vertical projection of the GRF
The center of pressure is equal and opposite to…?
The weighted average of all the downward forces acting on the area in contact with the ground
What are the MSK contributions to balance control?
- Postural alignment
- Musculoskeletal flexibility
- Sensation
What are the components of musculoskeletal flexibility that contributes to the MSK contributions to balance control?
ROM, muscle performance, etc
Balance is ____
Balance is postural stability
What are the two main types of momentum?
- Linear
- Angular
What is linear momentum?
The linear velocity of a body along a straight path
What is angular momentum?
The rotational velocity of the body
What are the components that controls balance?
- MSK system
- Nervous system
- Contextual effects
What are the components of sensation that contributes to the MSK contributions to balance control?
Touch, pressure, vibration,
proprioception
The neuromuscular contributions of balance control is responsible for what?
Sensory processing for perception of body orientation
What are the sensory processing components of balance control?
Visual, vestibular, somatosensory
The neuromuscular contributions to balance control is also responsible for what?
- Sensorimotor integration
- Motor strategies for planning,
programming, and executing
balance response
What are the contextual contributions to balance control?
- Environment
- Support surface
- Lighting
- Task characteristics
What are the 2 types of environments that contribute to balance control?
- Closed
- Open
An open environment is __, while a closed environments is ____
An open environment is *unpredictable with
distractions* while a closed environments is predictable with no distractions
What 3 systems comprise our balance?
Visual System
Somatosensory System
Vestibular System
The visual system provides information regarding…?
- Position of the head relative to the environment
- Orientation of the head to maintain level gaze
- Direction and speed of head movements
The somatosensory system provides information about ___
Position and motion of the body and body parts relative to each other and support surface
What do muscle spindles, golgi tendon, and joint receptors tell us?
What the muscle length and position is at any given time
Muscle spindles, golgi tendon, and joint receptors are sensitive to ___
Muscle spindles, golgi tendon, and joint receptors are sensitive to sensitive to muscle length and stretch
Skin mechanoreceptors are sensitive to ___
Skin mechanoreceptors are sensitive to vibration, light touch, deep pressure, etc.
The vestibular system measures the ___
The vestibular system measures the position and movement of the head with respects to gravity and inertial forces
What do the semicircular canals do?
Detect angular acceleration
What do the otoliths (utricle & saccule) canals do?
Detect linear acceleration
and head position
What is the primary processing region for balance?
Cerebellum
___ system has the fastest response time in regards to balance control
Somatosensory system has the fastest response time in regards to balance control
What are the types of balance control?
- Open Loop Motor Control
- Closed Loop Motor Control
- Anticipatory control
What is open loop motor control used for?
Utilized for movements that occur too fast to rely on sensory feedback (reactive responses) or for anticipatory aspects of postural control
What is closed loop motor control used for?
Utilized when precision movements that require sensory feedback (maintaining balance while sitting on a ball, or standing on tandem beam)
What does anticipatory control involve?
Involves activation of postural
muscles in advance of performing skilled movements
___ balance control is automatic and is carried out with no feedback
Open loop motor control balance control is automatic and is carried out with no feedback
What are the primary motor strategies used by healthy adults to recover balance in response to sudden perturbation?
- Ankle strategy
- Hip strategy
- Stepping strategy
What are the movement systems that each primary motor system uses to regain balance?
- Reflex
Automatic - Voluntary
What is the mediating pathway of the reflex movement system for balance control following perturbation?
Spinal cord
What is the mediating pathway of the automatic movement system for balance control following perturbation?
Brain stem/ subcortical
What is the mediating pathway of the voluntary movement system for balance control following perturbation?
Cortical
What is the mode of activation of the reflex movement system for balance control following perturbation?
External stimulus
What is the mode of activation of the automatic movement system for balance control following perturbation?
External stimulus
What is the mode of activation of the voluntary movement system for balance control following perturbation?
External or self stimulus
What is the comparative latency of response of the reflex movement system for balance control following perturbation in regards to the other systems?
Fastest
What is the comparative latency of response of the automatic movement system for balance control following perturbation in regards to the other systems?
Intermediate
What is the comparative latency of response of the voluntary movement system for balance control following perturbation in regards to the other systems?
Slowest
What is the response of the reflex movement system for balance control following perturbation?
Localized to point of stimulus and highly stererotyped
What is the response of the automatic movement system for balance control following perturbation?
Coordinated among leg and trunk muscles; stereotypical but adaptable
What is the response of the voluntary movement system for balance control following perturbation?
Coordinated and highly variable
What is the role in balance of the reflex movement system for balance control following perturbation?
Muscle force regulation
What is the role in balance of the automatic movement system for balance control following perturbation?
Resist disturbances
What is the role in balance of the voluntary movement system for balance control following perturbation?
Generate purposeful movements
What are the factors modifying the response of the reflex movement system for balance control following perturbation?
MSK or neurological abnormalities
What are the factors modifying the response of the automatic movement system for balance control following perturbation?
MSK or neurological abnormalities; configuration of support; prior experience
What are the factors modifying the response of the voluntary movement system for balance control following perturbation?
MSK or neurological abnormalities; conscious effort; prior experience; task complexity
____ movement system for balance control following perturbation is the 1st system to respond to a fall
Automatic movement system for balance control following perturbation is the 1st system to respond to a fall
Movements at the ankle act to restore a person’s ____
Movements at the ankle act to restore a person’s CoM to a stable position
For small external perturbations that cause a loss of balance in a forward reaction, muscle activation usually proceeds in a ___ to ___ sequence
For small external perturbations that cause a loss of balance in a forward reaction, muscle activation usually proceeds in a distal to proximal sequence
In what order do muscles in the ankle strategy responds in a distal to proximal sequence in a forward reaction?
Gastroc 1st, then hamstrings, then paraspinals
In what order do muscles in the ankle strategy responds in a distal to proximal sequence in a backward reaction?
Tibialis anterior 1st, then quads and abdominals
What strategy does the body use with a rapid or large perturbation?
Hip strategy
What does the hip strategy do?
Uses rapid hip flexion or extension to move the CoM within the BoS
In what sequence are muscles activated in response to a forward/backwards body sway in the hip strategy?
Proximal to distal sequence
What muscles are activated in response to a forward body sway in the hip strategy?
Abdominals followed by the quads
What muscles are activated in response to a backwards body sway in the hip strategy?
Paraspinals followed by the hamstring
The step strategy is used to ___
The step strategy is used to prevent a fall
When do we use the step strategy?
When perturbations are fast, are large amplitude, or when other strategies fail
What is the lateral plane movement strategy?
Weight shift strategy
What does the weight shift strategy do?
Shift weight from one leg to the other
What is the key control point of the weight shift strategy?
Hips
When is the suspension strategy utilized?
When a person quickly lowers their CoM, by flexing the knees ankles and hips
The suspension strategy can be combined with___ to enhance the effectiveness of balance and control
The suspension strategy can be combined with weight shift to enhance the effectiveness of balance and control
What causes impaired balance?
Anything that affects the components of information processing
What are the components of information processing?
- Sensory input
- Sensorimotor integration
- Motor output
What are the sensory input impairments?
- Proprioceptive deficits
- Reduced somatosensation
- Visual loss
- Vestibular damage
Individuals with a reduced somatosensation tend to rely more on the ___ strategy to maintain their balance
Individuals with a reduced somatosensation tend to rely more on the hip strategy to maintain their balance
Sensorimotor integration impairments usually stems from ___
Sensorimotor impairments usually stems from *damage to
the basal ganglia, cerebellum, or supplementary motor area*
Sensorimotor integration impairments results in an ___
Sensorimotor integration impairments results in an over-reliance on one particular sense
What can cause deficits in the motor output balance?
MSK or NM issues
___ common and major cause of morbidity, mortality,
reduced function, and premature nursing home admission in the older population
Falls common and major cause of morbidity, mortality,
reduced function, and premature nursing home admission in the older population
What are the intrinsic fall risk factors in the elderly?
- Advanced age
- Previous falls
- Muscle weakness
- Gait and balance problems
- Poor vision
- Postural hypotension
- Chronic conditions including arthritis, diabetes, stroke, parkinson’s, incontinence, dementia
- Fear of falling
What are the extrinsic fall risk factors in the elderly?
- Lack of stair handrails
- Poor stair design
- Lack of bathroom grab bars
- Dim lighting or glare
- Obstacles and tripping hazards
- Slippery or uneven surfaces
- Psychoactive medications
- Improper use of ADs