Quiz 3.5

Question 1

Balance

Answer 1

Keeping your body upright and stable
Dynamic OR static

Question 2

Static Balance

Answer 2

Maintaining upright posture while being ‘still’
Ex: Standing

Question 3

Dynamic balance

Answer 3

Maintaining upright posture while moving
Ex: walking

Question 4

What does balance do for us

Answer 4

Allows us to maintain upright alignment, efficient movement patterns, load joints symmetrically

Question 5

“good posture”

Answer 5

Least amount of energy expended

Question 6

Center of mass

Answer 6

Point around which the mass is considered to be concentrated, represents total mass
Can reference whole body or segments
Location determines response to external forces

Question 7

Center of gravity

Answer 7

Vertical projection of the COM on the ground

Question 8

Center of Pressure

Answer 8

Point representative of the location of the average vertical ground reaction force vector (where COG is on ground)
Location depends on muscular contributions and # of points of contact
Moves A/P and M/L

Question 9

Are A/P and M/L sway independent

Answer 9

No, they come in combo
Evert/invertors are also plantar/dorsiflexors (both planes)
Narrow foot means hip ab/add must assist to avoid loss of balance

Question 10

Inverted pendulum

Answer 10

Axis as feet, body as pendulum
This is how standing is characterized because of the sway

Question 11

Strategy to maintain upright posture

Answer 11

Vision providing us with reference points

Question 12

Base of Support

Answer 12

Comprised of the outermost edge of points of contact with the ground

Question 13

Key to balance

Answer 13

Keep your Com/COG within your base of support

Question 14

Perturbation

Answer 14

Application of external torque

Question 15

Strategies to maintain balance

Answer 15

Ankle, hip, stepping, suspensory
Automatic and happen 85-90 msec after instability is recognized

Question 16

Ankle strategy

Answer 16

Slow, low amplitude perturbation
Contact surface is wide and longer than foot
Muscles recruited distal –> proximal
Head in-phase with hips
SEE graph of muscles

Question 17

Hip Strategy

Answer 17

Fast, large amplitude perturbation
Surface is unstable or shorter than feet
Muscle recruited proximal–>distal
Head out-of-phase with hips (opp. direction)
SEE graph of muscles

Question 18

Stepping strategy

Answer 18

Used to prevent fall (magnitude of force too large or fast and/or other strategies fail)
BOS moves to catch up with COM

Question 19

Suspensory Strategy

Answer 19

Associated with large magnitude force
Forward bend of trunk (knee/hip flexion) progress into squat
COG lowered
Lower Cog means less ramifications if fall

Question 20

Factors that influence stability

Answer 20

BOS
Vertical displacement of COM (COG)
Location of COG relative to BOS

Question 21

When do we have greatest stability

Answer 21

COG close to the midline of BOS
Think athletic position

Question 22

What muscles control A/P sway

Answer 22

Flexor and extensor muscles

Question 23

What muscles control M/L sway

Answer 23

At ankle: invert/evertors
At hip: Ab/Adductors

Question 24

Feed forward

Answer 24

The feedback that muscles use for stability
Activation after perturbation is applied is too late

Question 25

Why is athletic stance popular (triple threat)

Answer 25

Increase BOS
Lower COM
Increase stability and places lower extremity joints flexed in active positions

Question 26

How do we help people who can’t use athletic position

Answer 26

Canes, crutches, walkers
These change the BOS and add contact point

Question 27

What is the key to life

Answer 27

Balance