Chapters 7 & 9 Flashcards
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
Alignment
Center of Mass
point at center of the total body mass
Center of Gravity
vertical projection of the center of mass
Center of Pressure
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 or balance
ability to control the center of mass in relationship to the base of support
Clinical definition of fall
an event that results in a person coming to rest inadvertently on the ground (unplanned or unexpected contact with a supporting surface)
Research definition of fall
movement of the CoM outside of the base of support (including stepping to recover stability)
How is the body controlled during quiet stance?
The CoP works to control the CoM moving the body backward and forward.
Feedback Control
postural control that occurs in response to sensory feedback (somatosensory, visual or vestibular) from an unexpected perturbation
Feedforward Control:
postural responses that are made in anticipation of a voluntary movement potentially destabilizing in order to maintain stability during movement
Synergy:
the functional coupling of groups of muscles that are constrained to ACT TEGETHER as a unit
Ankle Strategy, Forward sway:
to prevent falling on face, use posterior muscles to restore CoM
Ankle Strategy, Backward Sway:
to prevent falling on back, use anterior muscles to restore CoM
What is the timing of activation in the ankle strategy?
from distal to proximal muscles
What is the ankle strategy used for?
smaller perturbations
Hip strategy, forward sway:
to prevent falling on face, use large anterior muscles
Hip strategy, backward sway:
to prevent falling on back, use large posterior muscles
What is the timing activation in hip strategy?
from proximal to distal muscles
What is the hip strategy used for?
Useful for fast and large disturbance
Stepping strategy:
When the ankle and hip strategies are not enough to maintain the balance, a step will restore the CoM.
Lateral stability:
Mainly, muscles at the hip and trunk are used.
Muscle patterns are organized in a proximal-to-distal direction.
What is the cerebellum in control of?
adaptation – the ability to modify postural muscle amplitude in response to changing tasks and environmental conditions
What is the basal ganglia in control of?
postural set – the ability to quickly change muscle patterns in response to changing tasks and environmental conditions
Factors contributing to aging:
primary or genetic
secondary or experiential
Primary or genetic factors
contribute to the loss of neuronal function within a system over which we have LITTLE control
Secondary or experiential factors
such as environment, nutrition, and lifestyle, affect our nervous system function over which we have MORE control
When perturbation size and velocity increase, stable order adults:
showed increased amplitude of response as compared to young adults
When perturbation size and velocity increase, unstable order adults
exhibited much more increased amplitude of response
What is balance performance correlated with:
sensory/motor system function,
muscle weakness,
impaired synergy of muscle coordination and response to instability,
and limitation to adapt movement in reaction to changing tasks
Compensatory step take in stepping reaction:
forward or backward stepping with one or more lateral
Compensatory step take in reaching reaction:
initiation of arm movement, reach-to-grasp movement
Sensory Weighting Hypothesis
When one sensory system is less reliable, the input to the CNS from that system is weighted less heavily, and inputs from other systems will be weighted more heavily
With age, vibratory sensation threshold:
increases
With age, tactile sensitivity
decreases
With age, visual threshold
increases
With age, visual acuity
decreases
