Postural Balance

Question 1

What is balance?

Answer 1

Ability to maintain gravity line of body within base of support with minimal postural sway

Question 2

What is sway?

Answer 2

Movement of CoM in the transverse plane, even when standing still

Question 3

How does human body behave in the quiet stance?

Answer 3

Acts as a inverted pendulum

Question 4

What are the 3 main categories of determinant factors for postural control?

Answer 4

Subject
Environmental Context
Task

Question 5

What are the expended determinant factors for postural control?

Answer 5

Adaptive mechanism
Anticipatory mechanisms
Sensory strategies
Individual sensory systems
Neuromuscular synergies
Musculoskeletal components
Internal representations

Question 6

What are the 3 sensory input systems involved in postural control?

Answer 6

Visual System

Vestibular System

Somatosensory System

Question 7

What are the pathways in postural control?

Answer 7

Visual, Vestibular & Somatosensory > CNS integration in (brain) > motor command and CNS integration in (body) > body carries out movements > constraints information carried back to 3 sensory systems

Question 8

How is sway measured?

Answer 8

COM: Motion capture system
CoP: Force platform

Question 9

What is the difference between CoM and CoP in measuring postural sway?

Answer 9

CoM excursion is gold standard truly represents,

CoP is measure of activity of motor system in moving CoP > neuromuscular response to CoM displacement (not true record of body sway)

Question 10

What happens during quiet standing and body is acting like an inverted pendulum?

Answer 10

If Wg > Rp, body will have clockwise angular acceleration (forward sway)

Subject will increase CoP to correct it (plantarflexion activation)

Now Rp > Wg, backward sway

Decreasing of CoP > decrease plantarflexion activation

COP range > CoM range

Question 11

What are the parameters measured in postural sway measurement?

Answer 11

Time domain: Excursion, range, speed, standard deviation, root mean square, 95 CI eclipse area

Nonlinear: Fractal dimension, entropy

Frequency: Fourier analysis

Question 12

What is the protocol for a postural sway test?

Answer 12

Barefoot

Standing in the upright position as still as possible

Upper limbs relaxed at the side of the body

Natural support area: approximately 3-5 cm between the heels and 20-25 cm
between the toes (variation: single-leg & tandem stances)

Duration: 20 to 30 seconds each trial (variation: up to 60s)

3 to 5 trials eyes open (EO condition); 3 to 5 trials eyes close (EC condition)

Data collected at 50Hz (variation: 100 to 200Hz)

Question 13

In a one leg stance test, how is the dominant leg determined?

Answer 13

Ball kick test

Step up test

Balance recovery test

At least 2/3 of 3 tests

Question 14

What are automatic postural responses?

Answer 14

Reactive movements to maintain one’s balance after perturbation

Question 15

What are 3 strategies of maintaining balance?

Answer 15

Ankle, hip, stepping

Question 16

When is ankle strategy used? How is it used?

Answer 16

Quiet stance or secondary to small perturbations

Normal support surface

Muscle activity (distal to proximal) initiated at ankle, radiating to thigh and abdominal muscles > producing torque in ankle

Question 17

When is hip strategy used?

Answer 17

Moderate perturbation OR support surface narrow relative to base of support, OR direct perturbation to pelvis

Ankle strat not effective because support surface too small

Muscles activated proximal to distal direction

Question 18

When is stepping strategy used?

Answer 18

When lower limb and torso cannot maintain CoM within base of support

Step increases base of support or realigns it

Question 19

Describe the mixed strategy of maintaining balance (automatic postural responses)

Answer 19

Sensory information measured by Multi Sensory Signals (3 sensory inputs) > sent to CNS process > Estimated body kinematics > appropriate control plans selected > motor commands produced as joint torques

Question 20

Describe the control mechanism: anterior posterior (ankle muscle control)

Answer 20

Difference between COP and COM is proportional to horizontal acceleration of COM

Question 21

Describe the control mechanism: medial-lateral (load/unload mechanism)

Answer 21

COPc (ankle mech) and COPv (load mech) are independent of each other

Question 22

What are the conditions that increase body sway?

Answer 22

Aging, 
neurological diseases (parkinsons)
fatigue
Muscle-skeletal conditions (osteoperosis)
Dementia diseases (alzeihmer's disease)
Poor physical fitness
Poor vision

Question 23

What did systematic review and meta analysis of Balance training reveal?

Answer 23

There’s a dose-response relationship.

BT > effective means to improve steady state and proactive balance

Duration: 11-12 weeks
Training frequency: 3x/week
Duration: 10-15 min / session
Amt of exercises: 4ex / session, 2 sets / exercise, 20-40s /exercise

Question 24

What are the findings in terms of balance training to unlearned balance task?

Answer 24

Balance training is task specific

Slackline training intervention > flamingo and slackline balance task pre and post training > flamingo & slackline standing time increased significantly

BUT effect size 3x larger in slackline & body balance improvement pre v post only in slackline task