Lecture 14

Question 1

Center of Gravity

Answer 1

refers to vertical projection of COM to the ground

located about the level of S2
approx 55% of person’s height
men = higher, wider shoulders
women = lower, wider pelvis

Question 2

Base of support

Answer 2

perimeter of the contact area between the body and its support surface

Question 3

Balance is greatest when

Answer 3

body’s COV is maintained over its BOS

Question 4

Limits of stability

Answer 4

the sway boundaries in which postural equilibrium is maintained without a change in the BOS

Question 5

Anteroposterior sway limit

Answer 5

12” from post to anterior

Question 6

Lateral sway limit

Answer 6

16” from side to side

Question 7

Balance

Answer 7

not particular position, but it is a space.

determined by size of support base, limitations of joint range, muscle strength, sensory info

Question 8

Balance is made up of

Answer 8

cognitive processing
biomechanical constraints
movement strategies
sensory strategies
orientation in space
control of dynamics

Question 9

Postural control

Answer 9

complex motor skill derived from the interaction of multiple sensorimotor processes

Question 10

Strategies for balance control

Answer 10

ankle
hip
stepping
suspension

Question 11

Ankle strategy

Answer 11

used when displacements of COG are small
displaces COG by creating rotation about ankle joint
used on firm surfaces
muscle contractions begin distal, progress to proximal

Question 12

Hip strategy

Answer 12

rapid hip flexion or extension to move the COG within BOS
used when ankle motion is impaired or ankle cannot compensate
surface is narrow or compliant
surface doesn’t allow ankle torque
muscles are activated proximal to distal

Question 13

Stepping strategy

Answer 13

if displacement is large enough, a forward, backward, or lateral step is used to regain postural control

people at risk of falling have a preferential use of stepping

Question 14

Suspension Strategy

Answer 14

rapid lowering of body by flexing knees
results in hip and ankle flexion
COG is lowered to maintain balance

Question 15

Environment/Contextual Factors w/balance

Answer 15

Environment, can be open or closed
support surfaces (lighting, gravity)
task characteristics

Question 16

musculoskeletal system contributions to postural control

Answer 16

joint ROM
joint integrity
muscle strength, power, endurance
flexibility

if any are impaired, it will be difficult to modify COG and put it back over BOS

Question 17

Nervous system contributions to balance

Answer 17

sensory = visual, vestibular, somatosensory
sensorimotor = link to motor sensations
motor strategies = planning, programming, executing

Question 18

Visual system

Answer 18

provides info regarding the position of the head relative to the environment

orientation of the head to maintain level gaze

direction and speed of head movements

Question 19

Vestibular system

Answer 19

provides info regarding orientation of the head with respect to gravity and inertia

receptors in ears responds to movements

cannot differentiate between nodding head and bending forward

Question 20

Somatosensory system

Answer 20

provides info about position and motion of the body and body parts relative to each other and the support surface

free nerve endings, mechanoreceptors, joint receptors, golgi tendon organs, muscle spindles

Question 21

How the body combines all its systems

Answer 21

Somatosensory = 70%
Vision = 10%
Vestibular = 20%

increased use of vision and vestibular when on unstable surface

Question 22

Push and release test

Answer 22

on a scale of 0 to 4, used on parkinson patients. Tests balance non-vestibular.

Question 23

Balance Error Scoring System

Answer 23

Double leg stance
single leg stance
tandem stance

you change the surface, from firm to foam surfaces
count the number of errors in each trial to obtain a score