balance and posture

Question 1

what is balance ?

Answer 1

keeping the centre of mass within the base support

Question 2

what happens if the COM moves outside the BOS?

Answer 2

we fall / compensatory step

Question 3

what force is create din our ankle joint when me lean forward ?

Answer 3

torque which helps with balance though active calf muscles

centre of pressure in our toes when we lean forward

Question 4

what is the relevancy of centre of pressure?

Answer 4

helps keep centre of mass within the boundaries

oscillates forward/back to maintain COM

Question 5

what are the 3 reasons why we sway ?

Answer 5

sensory estimation

motor output

external/internal perturbations

Question 6

how does sensory estimation effect swaying ?

Answer 6

sensor noise for movement can create inaccuracy

smooth movement is more useful not rough

Question 7

how does external/internal perturbations effect swaying ?

Answer 7

things like the wind or being pushed can create variability in our stability and swaying

Question 8

what 5 things help us stay upright ?

Answer 8

vision

touch/ tactile info

proprioception

vestibular system

efferent copy of motor command + prediction

Question 9

what control is best for slow control of sway ?

Answer 9

visual

Question 10

at control is best for bast control of sway ?

Answer 10

vestibular

Question 11

what happens to our sway if we remove vision and why?

Answer 11

increases sway

reducing acuity - increase

blocking part of visual field - increase

Question 12

how doe sth equality of visual info effect balance ?

Answer 12

closer objects are more useful

further away objects produce no retinal motion

Question 13

what is motion parallax ?

Answer 13

objects appear to move relative to each other depending on the focus point

more cluttered environment increases sway

Question 14

what is visual vection?

Answer 14

false sense of motion induced by a. moving scenes

e.g. seeing train move, thinking your own train is moving

Question 15

if a room is moved to the right which way do we fall ?

Answer 15

left

we sway the opposite direction to compensate

Question 16

how does habituation to a moving room effect our sway ? (3)

Answer 16

repeated exposure makes ups more aware and prepared

allows visual responses to be ignored

swaying can be overridden by cognitive control

Question 17

what are the characteristics of visual perturbation?

Answer 17

initial sway - in direction of visual field movement 1s after onset

corrective sway- swaying in opp direction after 2-3s

Question 18

what happens when the visual field motion is ambiguous during visual perturbation?

Answer 18

brain must interpret each visual stimulus and distinguish between each object

involves expectation and prior knowledge

Question 19

what did research into sensory removal on postural responses reveal ? (3)

Answer 19

standing is possible with only proprioceptive input

BUT

balance reflexes are more effective with all senses available

balance reflexes can be tuned by intention

Question 20

what are the assumptions about passive ankle stiffness? (2)

Answer 20

assumes ankle is stuff enough to prevent falling

torque and angle are directly proportional in the Ankle

Question 21

what did research int passive ankle stiffness find ? (3)

Answer 21

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