Postural Control

Question 1

What are the two goals of orientation and stability

Answer 1

• Postural Orientation
• Postural Stability

Question 2

Postural Orientation

Answer 2

– Ability to maintain appropriate relationship between gravity, body and environment for a specific task
– Need a reference frame: Verticality, Orientation to the task
– Ex: Standing, automobile cart while lying down

Question 3

Postural Orientation relies on what?

Answer 3

Vision
Somatosensory
Vestibular

Question 4

PO- Vision Function

Answer 4

Peripheral & foveal (central) visual information
Position and motion of the head (optic flow) relative to environment
Frame of reference for verticality

Question 5

What is optic flow?

Answer 5

how light passes over the retina
(helps with orientation)

Question 6

____ vision is the most imporatn with position and flow of environment

Answer 6

peripheral

Question 7

PO - Visual Limitations

Answer 7

• Not always accurate for orientation (brain may misinterpret)
• Difficulty with exocentric (object motion) vs egocentric (self motion) motion
• Ex: Two vehicles on the side of you drive forward at the same time, you feel like you are going backward when in reality you are in the same place.

Question 8

PO - Somatosensory Function

Answer 8

• Position and motion information relative to supporting surface (Ex: floor, chair, especially horizontal; lean to left you feel more pressure on the left so it orients you)
• Relationship body segments to one another.

Question 9

PO - Somatosensory Limitations

Answer 9

• With moving surfaces or non horizontal it is less useful for orientation

Question 10

PO - Vestibular Function

Answer 10

• Postiion and movement of head with respect to gravity/inertial forces
• Provides a gravito-inertial frame of reference

Question 11

PO - Vestibular Limitation

Answer 11

• Alone cannot tell a true picture; easily tricked. Requires additional sensory system.
• Tilting head forward and having head in same position from hinging hips could relay the same information from the vestibular system.

Question 12

Postural Stability

Answer 12

• Defined as the ability to control COM relative to BOS
• Body relies on synergies to keep us upright. Brain tells self where to put CoM to keep stable so the muscle adjust to get that.

Question 13

Need to consider what 3 things for postural stability?

Answer 13

• COM position
• COM velocity
• BOS

Question 14

Describe this photo

Answer 14

• COM is from midfoot to toe
• How fast we move and how far will change our COM
• Stability limits are not a fixed entitiy.

Question 15

What are the 7 Factors that contribute to stability?

Answer 15

• Alignment
• Muscle Tone
• Postural Tone
• Anterior-Posterior
• Medial-Lateral
• Multidirectional
• Stepping

Question 16

Alignment - Stability

Answer 16

• Line of Center of Gravity is anterior in the upper body
• COM leads slightly anterior; If you went unconcious would lead to falling forward
• Gastroc/Soleus control the body to remain stable to not fall forward

Example: Bad Postural Alignment - Old lady hunched over, places her near the edge of her BoS. IF she gets slightly nudged will go over the BoS and may fall.

Question 17

Muscle Tone - Stability

Answer 17

• Need inherent regidity to keep us upright
• Free Ca2+ allow for myosin and actin to work
• Stretch Reflex (Spinal Cord): Standing swaying forward puts tension on gastroc and soleus, reflex kicks in activating those muscles to pull you back to be more stable

Question 18

Postural Tone - Stability

Answer 18

• Activity in antigraviry muscles counteract gravity
• Muscles tonically (always firing) active during quiet stance
• Uses synergies to control muscles to keep you upright (Ex: Glute, quadriceps, gastroc/soleus lead to extension)
• Requires sensory input;
  – Cutaneous input: Pressure on the bottom of the feet leads to extensor tone
  – Somatosensory: Tonic Neck Reflexes
  – Vestibular: Head orientation

Question 19

Tonic Neck Reflex

Answer 19

Input from neck and vestibular goes into brain stem and creates certain muscle activation patterns.

Question 20

Head Orientation

Answer 20

• Tells you where you are in space
• Vertical or Horizontal

Question 21

How do people response to balance challenges?

Answer 21

• Ankle Strategy (Syngery)
• Hip Strategy (Synergy)
• ML Hip Strategy (Synergy)
• Multidirectional
• Stepping

Question 22

Ankle Strategy

Answer 22

• Distal to proximal muscle activation
• Low velocity, small pertibations and firm surfaces

Question 23

Hip Strategy

Answer 23

• Larger, faster pertibations, compliant surfaces and small BOS

Question 24

What type of populations are more likely to use a hip strategy and why?

Answer 24

• Older Adults; Lose ankle mobility which leads them to transition away from ankle into hip strategies; Higher fall risk
• Hx of Ankle Sprain; Lose ankle mobility and leads to hip strategies

Question 25

ML Hip Strategy

Answer 25

* Primarily lateral movement of the pelvis * Synergistic activation in ML sway (hip ABDuctors: Glute Med and TFL; Hip ADDuctors) * Proximal to distal (head to hip to ankle) **Note: Gluteus medius weakness is a common finding and plays a large role in balance**

Question 26

Multidirectional

Answer 26

* More complex stratergy synergies than AP or ML but is a blend of both of them * **Important to work with patients in multiple directions**

Question 27

Stepping

Answer 27

* All strategies failed and COM has gone outside of BOS or COM moved too fast

Question 28

How do we provide interventions to help promote the strategies we want for balance?

Answer 28

* Give repeated exposure * Provide different environments * Remove one of the senses forcing them to recruit others. - Promote A-P postural sway strategies **Inability to constantly refine and optimize sensory information will result in loss of ability**

Question 29

More sway =

Answer 29

Less control

Question 30

Of somatosensory, vestibular and vision, what do older adults, children and **early learning/initial recovery** all rely on? | Quiet Stance

Answer 30

* Vision! Loss/decrease in vision leads to more sway * They may struggle with the ability to swtich between sensory mechanisms

Question 31

How is does an abscense of somatosensory affect quiet stance?

Answer 31

In the absense of stance results in more sway. Alterations in the feet, eye muscle, SCM, tib ant, etc effected.

Question 32

Is the vestibular system retrainable if lost?

Answer 32

Significant loss will be extremely difficult to recover from. Need to switch and need to amplify other senses.

Question 33

What is "reweighting" senses?

Answer 33

All for the heightening of some as one as been damaged. Adults are able to reweight quicker than kids and older adults as they are not as vision dominant

Question 34

During a pertibation, what is the primary sense used and why? What pt populations are affected?

Answer 34

* Somatosensory for horizontal! Vestibular for surface rotations (Ex: Wave on a boat) * It is the fastest * Diabetes Mellitus, ligaments injuries and ankle sprains

Question 35

What is a sensory orientation test like?

Answer 35

Six different conditions that mess with different sensory conditions.

Question 36

What is feedforward control - Posture | Anticipatory Postural Control

Answer 36

Feedforward control – postural muscle activity before a planned movement begins; body learns and knows hwo to change CoM to keep yourself balanced. Two phases: * Preparatory Phase (pre-planned burst of activity) * Compensatory Phase (refining based on feedback)

Question 37

How do we restore anticipatory postural control after an injury?

Answer 37

* **PRACTICE** * Facilitate **fast movements, heavier loads, arm raises, pushing and pulling for LE anticapatory reactions** (Use a metronome to get people moving quicker) * Slowly move them off ADs

Question 38

True or False: Focusing on an external target will allow for someone to have less sway

Answer 38

True

Question 39

Brainstem Nuclei - Postural Control

Answer 39

* Influence coordination of synergies * Influence postural tone * Integrate sensory information for posure and balance * Contributes to anticipatory control accompanying voluntary movements

Question 40

Cerebellum and Basal Ganglia have roles in ____ and ____ control

Answer 40

* Anticipatory * Feedback * **CBM** influences **postural muscle response amplitude** to changing task and environment * **BG** influences **muscle patterns** in response to task and environment

Question 41

Cortex - Posture

Answer 41

* Visual integration * High level planning