Posture Flashcards

1
Q

static posture

A
  • body and segments are aligned and maintained in certain positions
  • standing, sitting, lying, kneeling
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2
Q

dynamic posture

A
  • body/segments are moving

- walking, running, jumping, throwing, lifting

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3
Q

base of support (BoS)

A

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

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4
Q

postural control

A

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

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5
Q

afferent inputs for postural control

A
  • proprioceptive
  • vestibular
  • visual
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6
Q

efferent inputs for postural control

A

muscular contraction

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7
Q

primary goal of postural control

A

stabilize the head

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8
Q

reactive (compensatory) responses

A

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

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9
Q

proactive (anticipatory) responses

A

responses occur in anticipation of internally generated destabilizing forces

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10
Q

altered or absent inputs

A
  • posture may be altered
  • stability may be compromised
  • example: decreased sensation of LEs or post-injury
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11
Q

alterations in ____ can compromise posture

A

outputs

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12
Q

example of altered output

A

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

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13
Q

maintenance of standing posture is the result of ____ controls

A

dynamic

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14
Q

sensory perturbation

A

may be caused by altering visual input

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15
Q

mechanical perturbation

A

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

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16
Q

fixed support synergies/strategies

A

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

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17
Q

ankle synergy

A

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

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18
Q

hip synergy

A

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

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19
Q

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

A
  • minor perturbations

- small changes in terrain

20
Q

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

A

fast perturbation

21
Q

muscles activated in ankle strategy during forward sway

A
  • gastroc
  • hamstrings
  • paraspinals
22
Q

muscles activated in ankle strategy during backward sway

A
  • tib anterior
  • quads
  • abdominals
23
Q

muscles activated in hip strategy during forward sway

A
  • abdominals

- quads

24
Q

muscles activated in hip strategy during backward sway

A
  • paraspinals

- hamstrings

25
Q

change-in-support strategies

A
  • stepping and grasping strategies

- can move or enlarge the body’s BoS so it remains under the CoM

26
Q

stepping strategies

A
  • take a step to widen BoS

- forward, backward, or sideways

27
Q

grasping strategies

A

using one’s hands to grab a fixed surface

28
Q

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

A

change-in-support strategies (stepping and grasping)

29
Q

differences between young and old individuals in stepping strategies

A

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

30
Q

what produces internal forces?

A
  • muscle activity

- passive tension in ligaments, tendons, and joint capsules

31
Q

external forces include…

A
  • inertia
  • gravity
  • ground reaction forces
32
Q

equilibrium = sum of ____ and ____ forces equal to ____

A
  • internal
  • external
  • zero
33
Q

postural sway

A

constant swaying motion due to inertial and gravitational forces

34
Q

ground reaction force (GRF)

A
  • force of ground pushing back on the body in standing

- represents magnitude and direction of loading applied to one or both feet

35
Q

line of gravity (LoG)

A

line extending from center of gravity to BoS

36
Q

center of pressure (CoP)

A
  • point of application of the GRF

- located b/w the feet in BL stance

37
Q

what happens when LoG passes directly through joint axis?

A

no torque is created around the joint

38
Q

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

A
  • external gravitation moment

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

39
Q

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

A

increases

40
Q

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

A

location

41
Q

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

A
  • anterior

- proximal

42
Q

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

A
  • dorsiflexion (tibia moves forward)

- gastroc and soleus

43
Q

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

A

stronger

44
Q

LoG passes ____ to all joint axes, minimizing ____ moments

A
  • through or very close

- external

45
Q

what types of internal moments will balance external moments?

A
  • passive capsular and ligamentous tension
  • passive muscle tension
  • small, continuous amount of muscle activity
46
Q

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

A
  • excessive strain on passive structures

- increased muscular activity

47
Q

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

A

structural changes