week 13- 1

Question 1

biomechanical factors to increase stability

Answer 1

• increase the area of the base of support
• increased distance from the line of COG
• decrease of COM over base of support

Question 2

during quiet standing

Answer 2

maintain antigravity posture

Question 3

during unexpected perturbation

Answer 3

reactive balance

Question 4

during voluntary self-initiated movement

Answer 4

anticipatory postural control

Question 5

reactive balance

Answer 5

• postural control system come into play in response to a destabilizing external force or perturbation
  -utilizes feedback mechanism where the central nervous system responds to info received during and after a movements and attempt to restore stability

Question 6

muscle synergy

Answer 6

particular muscles work together (in synergy) to achieve the task; in the case of reactive balance, it occurs without voluntary control
- muscles involved in the synergy depend on the requirement of the task

Question 7

ankle strategy

Answer 7

involves distal to the proximal sequence of muscles activation
- rotate about ankle only- body stays straight

Question 8

hip strategy

Answer 8

involves proximal to distal activation
- rotate about hip only - legs and torso stay straight

Question 9

suspensory strategy

Answer 9

crouch down- mostly observed on young children (reflective)

Question 10

step strategy

Answer 10

take a step because move outside the limits of stability

Question 11

reactive balance context dependent

Answer 11

• small balance perturbations usually result in the use of an ankle strategy
• as perturbation gets larger, there is a switch to hip strategy and finally stepping strategy

Question 12

if the support surface is changed to a narrow beam

Answer 12

use hip strategy at a smaller perturbation magnitude

Question 13

aging associated with

Answer 13

reduced muscle strength and sensory function
-increased postural sway
—– particularly in fallers

Question 14

response to perturbation are slower with _____ muscle activity

Answer 14

greater

Question 15

hypermetria

Answer 15

condition of the dysfunction in which voluntary muscular movements tend to result in the movement of bodily parts (as the arm and hand) beyond the intended goal

Question 16

sensory contribution to postural control

Answer 16

effective postural control requires more than the ability to generate and apply forces and activate appropriate musculature

Question 17

to know when and how to apply forces or to activate appropriate muscles
the

Answer 17

CNS must have an accurate picture of where the body is in space and what forces are acting on it

Question 18

3 primary sources of peripheral input (to detect body position and movement relative to space and the environment

Answer 18

1. visual system
2. vestibular system
3. somatosensory/ proprioception

Question 19

The contribution of each sensory system is typically assessed by

Answer 19

1. removing or altering/ distorting the sensory information available
2. using patients population where it is absent or distorted

Question 20

Typically assess the involvement in different settings/contexts. Two common methods

Answer 20

(1) Quiet standing (COM or COP)
(2) External perturbations – Re-active

Question 21

vision

Answer 21

• no visual input postural sway increases between 30-40%

Question 22

Physical Perturbation

Answer 22

With eyes closed COM displacement is greater following linear translation of support surface beneath feet

Question 23

Visual Perturbation

Answer 23

Linear vection. E.g., Sitting in a car, car next to you starts to move, and you perceive that your car is actually moving

Question 24

moving room

Answer 24

optic flow important
moving line creates the illusion that person is moving forward shift COM backwards

Question 25

is vision involved in quiet standing

Answer 25

yes

Question 26

how do we know

Answer 26

Remove vision, greater sway, as indicated by greater movement of the COP/COM
Alter optic flow to give the illusion that a person is swaying in one direction, they
will move the COM in the opposite direction