Balance Flashcards
Balance / Postural stability
Describes the dynamic process by which the body’s position is maintained in equilibrium
Equilibrium
Body is either at rest (static equilibrium) or in steady-state motion (dynamic equilibrium)
When is balance the greatest?
When the body’s COM or COG is maintained over its BOS
Postural Orientation
The ability to maintain the appropriate alignment of body segments, and also refers to the body relationship to the environment for a task
Postural Control
The control of the body’s position in space to maintain orientation and stability
Center of Mass (COM)
A point that corresponds to the center of the total body mass and is the point at which the body is in perfect equilibrium
How is COM determined?
By finding the weighted average of the COM of each body segment
Center of Gravity
Vertical projection of the COM to the ground (most adults just anterior to S2)
Momentum
Product of mass times velocity
Linear momentum
Relates to the velocity of the body along a straight path
(sagittal or transverse plane)
Angular momentum
Relates to the rotational velocity of the body
Base of Support (BOS)
Perimeter of the contact area between the body and it’s support surface
What alters the BOS?
Foot placement; changing a person’s postural stability
Limits of Stability
Refers to the sway boundaries in which an individual can maintain equilibrium w/out changing his/her BOS
Ground reaction force
Follows Newton’s law of reaction; the contact between our bodies and the ground due to gravity (action forces) is always accompanied by a reaction from it
Center of Pressure (COP)
The location of vertical projection of the ground reaction force
Equal and opposite to weighted average of all the downward forces acting on the area in contact w/ the ground
What does COP reflect?
The body’s neuromuscular responses to imbalances of the COG
Balance is a complex process that emerges from what?
-Personal factors
-Environmental factors
-Postural control demands of the task
Personal factors
-Physiological systems, cognition, and psychological factors
What are the 3 systems that impact balance control?
-Nervous system (neurological)
-Musculoskeletal system
-Contextual effects
NS provides
-Sensory processing
-Sensorimotor integration
-Motor strategies
-Adaptive mechanisms
-Anticipatory mechanisms
Musculoskeletal contributions
-Postural alignment
-ROM flexibility
-Sensation
-Joint integrity
-Muscle performance
Contextual effects
-Environment
-Support surface
-Gravity
-Lighting
-Task characteristics
Cardiovascular system role
Contributes to balance by maintaining adequate brain perfusion to prevent loss of balance due to orthostatic hypotension or altered consciousness
Visual system Role
1) Position of head relative to environment
2) Orientation of the head to maintain level gaze
3) The direction and speed of head movement because as a person’s head moves, surrounding objects move in opposite direction
When can visual stimuli be used?
To improve a person’s stability when proprioceptive or vestibular inputs are not working properly
Somatosensory system Role
Provides info about the position and motion of the body and body parts relative to each other and the support surface
Muscle proprioceptors
Muscle spindles and GTOs
(sensitive to muscle length and tension)
Joint receptors
Pacinian and Ruffini
(sensitive to joint position, movement, and stress(
Skin Mechanoreceptors
(sensitive to vibration, light touch, deep pressure, and skin stretch)
What is the primary role of joint receptors?
To assist gamma motor system in regulating muscle tone and stiffness to provide anticipatory postural adjustments and counteract unexpected balance disturbances
Vestibular system Role
Provides info about the position and movement of the head with respect to gravity and inertial forces