KIN4070 Week 5 (Postural Control Continued)

What can be said about steady state balance?

• Body alignment can minimize the effect of gravitational forces

• Muscle tone keeps the body from collapsing in response to the gravity

  • Low muscle tone and high muscle tone can affect balance

    • Intrinsic stiffness of muscles

    • Background muscle tone

    • Postural Tone

What are the movement strategies for steady state balance?

• Stability limits: point at which a person will change the configuration of BOS to achieve stability

• Not fixed boundaries; change according to task

• Affected by position and velocity of COM

Hip strategy: to maintain COM within the base of support

Recover: by taking a step

What are the clinical applications of research in Steady State Balance?

• Berg Balance Scale

  • Picking up an object, standing on one foot

    • No reactive control tests

• Observing alignment of body segments

• Observing stability

• Observe how much COM move relative to BOS

Variance and variability: important to practice in different speeds.

What happens in reactive balance control?

• Motor patterns: ankle, hip, step and reach to grasp strategies

  • Ankle + hip: moving subway/ and having to stay ready

    • Fixed support

  • Reach to grasp + step: use this to catch themselves if falling

    • Change in support

• Fixed support versus change in support

• Synergy: functional coupling of groups of muscles constrained to act together as a unit

What is anterioposterior stability in reactive control?

• The stability gained by moving forward and backward

  • Ankle and Hip strategies, change in support strategies

What is mediolateral (ML) and multidirectional stability in reactive control?

• alignment of body segments and muscles requires activations of forces at different joints and in different directions to recover stability

• in all different planes

How are synergies of muscles refined in reactive balance control?

• Postural synergies not fixed, stereotypical reactions

• They are refined and tuned in response to changing demands in task and environment

• Adaptation: refining and tuning movements in response to task demands

The Cerebellum:

• expected sensory updates

• If anything happens to the structure, we should expect delays

What is reactive balance control in sitting like?

• Recovery of stability in the seated position controlled similarly to that in stance

• Individual muscles change their relative activation depending on the direction of instability

What are clinical applications of research in reactive balance control?

• Reactive balance: response to unexpected perturbation to stability

• Clinical tests of reactive balance

• Important not to limit training to activation of a single synergy

What is the input and output from the vestibulocerebellum?

• Input from vestibular apparatus

• Output to vestibular nuclei

• Output reaches LMN via vestibulospinal tracts and tracts that coordinate eye and head movements

What is the input and output from the spinocerebellum?

Input from spinal cord (trunk), vestibular nuclei, auditory and vestibular info (via brainstem nuclei) 

• output goes to vestibular and reticular nuclei and motor cortex (via thalamus)

• Output reaches LMN via vestibulospinal, reticulospinal and medial corticospinal tracts

What is the input and output from the spinocerebellum (paravermal section)?

• Input goes to spinal cord (from limbs)

• Output goes to red nucleus, motor cortex (via thalamus)

• Reaches LMN via Rubrospinal and lateral corticospinal tract

What is the input and output from the cerebrocerebellum (Lateral Cerebral Hemispheres)?

• input from cerebral cortex (via pontine nuclei)

• Output to motor and premotor cortex (via dentate nucleus and motor thalamus), red nucleus

• Reaches LMN by lateral corticospinal and corticobrainstem tracts, rubrospinal tract