balance and posture Flashcards
what is balance ?
keeping the centre of mass within the base support
what happens if the COM moves outside the BOS?
we fall / compensatory step
what force is create din our ankle joint when me lean forward ?
torque which helps with balance though active calf muscles
centre of pressure in our toes when we lean forward
what is the relevancy of centre of pressure?
helps keep centre of mass within the boundaries
oscillates forward/back to maintain COM
what are the 3 reasons why we sway ?
sensory estimation
motor output
external/internal perturbations
how does sensory estimation effect swaying ?
sensor noise for movement can create inaccuracy
smooth movement is more useful not rough
how does external/internal perturbations effect swaying ?
things like the wind or being pushed can create variability in our stability and swaying
what 5 things help us stay upright ?
vision
touch/ tactile info
proprioception
vestibular system
efferent copy of motor command + prediction
what control is best for slow control of sway ?
visual
at control is best for bast control of sway ?
vestibular
what happens to our sway if we remove vision and why?
increases sway
reducing acuity - increase
blocking part of visual field - increase
how doe sth equality of visual info effect balance ?
closer objects are more useful
further away objects produce no retinal motion
what is motion parallax ?
objects appear to move relative to each other depending on the focus point
more cluttered environment increases sway
what is visual vection?
false sense of motion induced by a. moving scenes
e.g. seeing train move, thinking your own train is moving
if a room is moved to the right which way do we fall ?
left
we sway the opposite direction to compensate
how does habituation to a moving room effect our sway ? (3)
repeated exposure makes ups more aware and prepared
allows visual responses to be ignored
swaying can be overridden by cognitive control
what are the characteristics of visual perturbation?
initial sway - in direction of visual field movement 1s after onset
corrective sway- swaying in opp direction after 2-3s
what happens when the visual field motion is ambiguous during visual perturbation?
brain must interpret each visual stimulus and distinguish between each object
involves expectation and prior knowledge
what did research into sensory removal on postural responses reveal ? (3)
standing is possible with only proprioceptive input
BUT
balance reflexes are more effective with all senses available
balance reflexes can be tuned by intention
what are the assumptions about passive ankle stiffness? (2)
assumes ankle is stuff enough to prevent falling
torque and angle are directly proportional in the Ankle
what did research int passive ankle stiffness find ? (3)
stiffness is too low to permit passive standing
limiting factor in stiffness is the tendon and soft tissues of the foot
stiffness not changed by intention or sensation
