Chapter 7 Flashcards
What is the clinical definition of a fall?
An even that results in a person coming to rest inadvertently on the ground (unplanned or unexpected)
What is the research definition of a fall?
Movement of the COM outside of the BOS
What are the 6 main strategies to maintain balance?
1) Controlling body sway
2) Feedback control
3) Feedforward control
4) Anteroposterior stability
5) Lateral stability
6) Multidirectional stability
How does our body control body sway?
The COP works to control the COM moving the body backward and forward
What is feedback control?
Postural control that occurs in response to sensory feedback from an unexpected perturbation
What is feedforward control?
Postural responses made in anticipation of a voluntary movement potentially destabilizing in order to maintain stability during movement
What is a synergy?
Functional coupling of groups of muscles that are constrained to act together as a unit
What muscles contract during ankle strategy?
Forward = POST (paraspinals, hamstrings, gastroc) Backward = ANT (abdominals, quads, tibialis anterior)
What order do the muscles activate during ankle strategy?
Distal to proximal
When is ankle strategy useful?
In small perturbations
What muscles contract during hip strategy?
Forward = large ANT (abdominals, quads) Backward = large POST (paraspinals, hamstrings)
What order do the muscles activate during hip strategy?
Proximal to distal
When is hip strategy useful?
Large, fast disturbances
What 3 strategies are included within anteroposterior stability?
Ankle strategy
Hip strategy
Stepping strategy
What occurs during stepping strategy?
When ankle and hip strategies aren’t enough to maintain balance, a step will restore COM
T/F Hip and ankle strategies cannot be combined.
False, they are combined in a continuous way
What is lateral stability?
An alternative strategy to recover stability in the ML direction
What muscles are used in lateral stability, and in what order?
Muscles at the hip and trunk
Proximal to distal
What is multidirectional stability?
A continuum of response patterns that control stability in the 360 degree continuum of possible perturbation directions
T/F Muscles can belong to more than one pattern of movement or synergy in multidirectional stability.
True
According the Dynamic Systems Model, what factors make up postural control?
- Musculoskeletal components
- Internal representations
- Adaptive mechanisms
- Anticipatory mechanisms
- Sensory strategies
- Individual sensory systems
- Neuromuscular synergies
What is the cerebellum’s role in postural stability?
Controls adaptation, the ability to modify postural muscle amplitude in response to changing tasks and environmental conditions
What is the basal ganglia’s role in postural stability?
Controls postural set, the ability to quickly change muscle patterns in response to changing tasks and environmental conditions
What is the brainstem’s role in postural stability?
Controls level of postural tone in combination with the cerebellum. Circuits for autonomic postural synergies. Vestibular contributions
What occurs in the spinal preparation area?
Ground reaction forces for orientation present, though diminished
Tonically active extensor muscle for antigravity support for postural orientation
No lateral stability
Somatosensory contributions
Why are perceptual systems needed in postural control?
In order for the body to know when and how to apply restoring forces, the CNS must have an accurate picture of where the body is in space and whether the body is stationary or in motion.
What are the 3 sensory inputs that contribute to postural control?
Visual
Somatosensory
Vestibular
Why are visual inputs necessary?
The give the relationship of our body to objects in the environment
What do visual inputs help position?
Position and move the head with respect to the surrounding objects (direction and speed)
Why are somatosensory inputs important?
The provide a surface of support
What do somatosensory inputs help to position?
Position and movement about the body with reference to BOS, relationship of body segments to one another
Why are vestibublar inputs important?
They help provide a sense of gravity
What do vestibular inputs help to position?
Postion and movement of the head with respect to gravity and inertial forces (angular acceleration)
What happens when one of the sensory systems is less reliable?
Input to the CNS from the system is weighted less heavily, and inputs from other systems are weighed more heavily
Alignment
Relationship of body segments to one another, as well as to the position of the body with reference to gravity and the base of support
COM
Point at center of total body mass
COG
Vertical projection of the center of mass
COP
Center of distribution of total force applied to supporting surface
Posture
the biomechanical alignment of the body and the orientation of the body in the environment.
Postural Control
Control of the body’s position in space for orientation and stability
Postural Tone
Activity increases in antigravity muscle, which keeps the body from collapsing in response to the pull of gravity during quiet stance.
Postural Orientation
Ability to maintain an appropriate relationship between body segments, and between the body and the environment for a specific task
Postural Stability/Balance
Ability to control the center of mass in relationship to the base of support
