Posture

Question 1

static posture

Answer 1

• body and segments are aligned and maintained in certain positions
• standing, sitting, lying, kneeling

Question 2

dynamic posture

Answer 2

• body/segments are moving

- walking, running, jumping, throwing, lifting

Question 3

base of support (BoS)

Answer 3

area bounded posteriorly by the tips of the heels and anteriorly by a line jointing the tips of the toes

Question 4

postural control

Answer 4

maintenance of center of mass (CoM) over BoS to control body’s orientation in space and stabilize head with respect to vertical to orient gaze

Question 5

afferent inputs for postural control

Answer 5

• proprioceptive
• vestibular
• visual

Question 6

efferent inputs for postural control

Answer 6

muscular contraction

Question 7

primary goal of postural control

Answer 7

stabilize the head

Question 8

reactive (compensatory) responses

Answer 8

responses occur as reactions to external forces that displace the body’s CoM

Question 9

proactive (anticipatory) responses

Answer 9

responses occur in anticipation of internally generated destabilizing forces

Question 10

altered or absent inputs

Answer 10

• posture may be altered
• stability may be compromised
• example: decreased sensation of LEs or post-injury

Question 11

alterations in ____ can compromise posture

Answer 11

outputs

Question 12

example of altered output

Answer 12

inability of muscles to respond appropriately to signals from CNS due to a neuromuscular disorder

Question 13

maintenance of standing posture is the result of ____ controls

Answer 13

dynamic

Question 14

sensory perturbation

Answer 14

may be caused by altering visual input

Question 15

mechanical perturbation

Answer 15

displacement causing changes in the relationship of the body’s CoM to BoS

Question 16

fixed support synergies/strategies

Answer 16

centrally organized patterns of muscle activity that occur in response to perturbations of standing postures

Question 17

ankle synergy

Answer 17

discrete bursts of muscle activity that occur in a distal-to-proximal pattern

Question 18

hip synergy

Answer 18

discrete bursts of muscle activity that occur in a proximal-to-distal pattern

Question 19

when would an ankle synergy be helpful for maintaining standing posture?

Answer 19

• minor perturbations

- small changes in terrain

Question 20

when would a hip synergy be helpful for maintaining standing posture?

Answer 20

fast perturbation

Question 21

muscles activated in ankle strategy during forward sway

Answer 21

• gastroc
• hamstrings
• paraspinals

Question 22

muscles activated in ankle strategy during backward sway

Answer 22

• tib anterior
• quads
• abdominals

Question 23

muscles activated in hip strategy during forward sway

Answer 23

• abdominals

- quads

Question 24

muscles activated in hip strategy during backward sway

Answer 24

• paraspinals

- hamstrings

Question 25

change-in-support strategies

Answer 25

- stepping and grasping strategies | - can move or enlarge the body's BoS so it remains under the CoM

Question 26

stepping strategies

Answer 26

- take a step to widen BoS | - forward, backward, or sideways

Question 27

grasping strategies

Answer 27

using one's hands to grab a fixed surface

Question 28

what is the only strategy that is successful with a large perturbation?

Answer 28

change-in-support strategies (stepping and grasping)

Question 29

differences between young and old individuals in stepping strategies

Answer 29

young people usually only take one step whereas older individuals more commonly take multiple, shorter steps

Question 30

what produces internal forces?

Answer 30

- muscle activity | - passive tension in ligaments, tendons, and joint capsules

Question 31

external forces include...

Answer 31

- inertia - gravity - ground reaction forces

Question 32

equilibrium = sum of ____ and ____ forces equal to ____

Answer 32

- internal - external - zero

Question 33

postural sway

Answer 33

constant swaying motion due to inertial and gravitational forces

Question 34

ground reaction force (GRF)

Answer 34

- force of ground pushing back on the body in standing | - represents magnitude and direction of loading applied to one or both feet

Question 35

line of gravity (LoG)

Answer 35

line extending from center of gravity to BoS

Question 36

center of pressure (CoP)

Answer 36

- point of application of the GRF | - located b/w the feet in BL stance

Question 37

what happens when LoG passes directly through joint axis?

Answer 37

no torque is created around the joint

Question 38

what happens when LoG passes at a distance from the joint axis?

Answer 38

- external gravitation moment | - results in rotation around the joint axis unless opposed by a counterbalancing internal moment or muscle contraction

Question 39

magnitude of external moment ____ as the distance between LoG and joint axis increases

Answer 39

increases

Question 40

direction of rotation depends on the ____ of the LoG in relation to the joint axis

Answer 40

location

Question 41

if LoG is anterior to joint axis, external moment will cause ____ motion of the ____ segment supported by that joint

Answer 41

- anterior | - proximal

Question 42

when LoG is anterior to ankle, gravity creates a ____ moment and the ____ muscles contract to counteract this moment

Answer 42

- dorsiflexion (tibia moves forward) | - gastroc and soleus

Question 43

more distance b/w LoG and AOR = ____ counteracting muscle contraction

Answer 43

stronger

Question 44

LoG passes ____ to all joint axes, minimizing ____ moments

Answer 44

- through or very close | - external

Question 45

what types of internal moments will balance external moments?

Answer 45

- passive capsular and ligamentous tension - passive muscle tension - small, continuous amount of muscle activity

Question 46

large deviations in the location of LoG relative to the joint axis result in...

Answer 46

- excessive strain on passive structures | - increased muscular activity

Question 47

long-term deviation in the location of LoG relative to the joint axis results in...

Answer 47

structural changes