posture and balance Flashcards
what is balance
quiet standing - involving keeping the centre of mass within the base of support
what allows the body to stand in the inverted pendulum model of human standing
using torque provided by active calf muscles
what is the equation for inverted pendulum stance
F= MG
force= mass x gravitational constant
center of gravity or mass is what
a point the mean position of the matter in a body or system
what is the centre of pressure
a point on a surface through the resultant force applies total pressure force
Centre of pressure oscillates forward and back to maintain…
centre of mass - sway can be quantified by com
standing is a what control process
sensorimotor
what are the 3 things for why we sway
sensory estimation
motor output
external and internal perturbations - b
what 5 things keep us upright
vision
proprioception
vestibular apparatus
touch
efference copy of motor command and prediction
2 different frequency control .. are…
slow / low frequency - visual control
fast/ high frequency for vestibular input
removing visual information cause’s the body to..
sway
quality of visual input can also effect
sway
distant visual information is useless for balance - t or f and why
t - no retinal motion
what is motion parallax
objects appear to move relative to each other
depending on focus point
objects appear to move relative to each other when we sway bc it
provides more information
the largest reduction is observed when foreground and background scenery are .
present together and furthest apart
what is perturbing visual input- visual vection
a false sense of motion induced by a false scene
what is this an example of
watching an adjacent train depart the station
visual vection
visual vection may impact what
sway and standing control / posture
subjects sway in the direction of
visual scene movement
the brain interprets forward scene motion as … and creates …..
backward body motion ….a compensatory forward response
effect of predictability on visual response
experimental triggers motion unexpectantly what response
big sway
ankle creates torque around calf to help prevent the body doing what
toppling forward
changes in muscle stiffness represent changes in what
muscle reflexes
removal of sensory information effects what
posture
muscle stiffness and balance is reduced with less
sensory information (visual and no vestibular)
ankle torque increases as the angle of ankle …
increases
the stiffness in the ankle is too low to permit
passive standing - standing without active modulation of emg
balance involves keeping com within
base of support
sway occurs mostly at which joint
ankle
sway arises from
lack of sensory information
