Theories of Motor Control Flashcards
Define Motor Control
- The study of the nature and cause of movement (healthy) and movement abnormalities
- Time frame = milliseconds (ms) or seconds (s) (unless repeated, continuous movements)
Theory #1 or Version #1: Systems-Based Task-Oriented Model —per Shumway-Cook and Wollacott
- The goal of motor control is to accomplish a motor task
- Movement is organized around a behavioral goal
- Patients must work on functional tasks [MAIN GOAL]
- -Encourages the body to engage in motor activity
- Interaction between the individual, task and environment
Systems-Based Task-Oriented Model:
Example-Apply to POSTURE
Individual:
Typical (“normal”) postural movement strategies - what should they be?
Observe this patient’s abnormal balance strategies
Does this client have any musculoskeletal, sensory, etc. constraints that should be considered?
Task:
What are the goals of this task? (feedback or feed-forward balance? Static, dynamic or protective balance?)
Environment:
List the types of environment that this client should have experience with in the clinic in order to enhance success in the home environment?
Theory #2 or Version #2: Systems Model
Horak
- Movements are organized around a behavior or goal
- Movements arise out of an interaction between
1. Normal movement strategies (Typical) [Individual]
2. Compensatory strategies [Individual]
3. Musculoskeletal constraints [Individual]
4. Central set/predictive control [Individual]
5. Environmental adaptation
6. Behavioral goals
Neuromuscular synergies
Standing Posture - ankle, hip and stepping strategies
Neuromuscular synergies - Standing
-Ankle strategy***: surface is firm perturbations are small -Hip strategy: softer or less firm surface [foam] larger perturbations -Stepping strategy: very pliable surface perturbations move COM beyond BOS
-Important: normally one can shift easily between the three strategies
Healthy adults can use an ankle strategy to recover from as much as …
8-10 dg of forward sway and 4-5 dg of backward sway
Ankle strategy: Muscle recruitment order
-Distal to Proximal
-20-40 ms delays between ankle, thigh & trunk muscles
-Forward sway: turn on posterior mm
GS -> HS ->Paraspinal/back mm
-Backward sway: turn on anterior mm to prevent falling backwards
Tib Ant -> Quads -> Abs
Systems Model (Horak): Compensatory Strategies (Individual)
- Individuals with neurological impairments have found the most appropriate, efficient and effective compensatory strategy given the constraints imposed by their damaged neuromusculoskeletal systems
- If you take away their compensatory strategy, you are responsible to help the patient replace it with a “typical” or other movement strategy
- Example: CVA patient with stiff ankle or AFO; re-learn gait pattern or ankle strategy with “free” ankle movement
Compensatory versus Recovery Focus
- Early after injury or trauma -> Focus on Recovery interventions
- Later, if recovery is limited -> Focus on Compensation interventions?
Compensatory versus Recovery Focus
Other Path…
- Early after injury or trauma -> Focus on Compensation interventions just so patient is functional at home (also teach family how to assist patient)?
- Next phase after injury or trauma -> Focus on Recovery interventions?
- Later, if recovery is limited -> Focus on Compensation interventions?
Systems Model (Horak): Musculoskeletal Constraints (Individual)
- How much of the movement problem is due to musculoskeletal problems rather than neural constraints?
- “Neuro” therapists are obligated to be experts in musculoskeletal examination, evaluation and intervention
- Treat the musculoskeletal complaint and then re-exam the movement pattern
Example: Musculoskeletal Component as applied to Posture and Balance
(Horak)
- Lower extremity loss of joint PROM & AROM
- Ankle contracture = limited ability to utilize ankle strategy > rather, use “early” hip or stepping strategy
- Treat the ankle contracture or underlying system or impairment and then re-assess balance ankle strategy
- Don’t treat a system in isolation
Systems Model
(Horak):
Central Set and Predictive Control (Individual)
- Central Set: An internal model of one’s body dynamics and the dynamics of the external world
- -Example: Predict that the trunk must accommodate for an upcoming UE movement (Feed-forward)
- Predictive Control: Knowing both your internal model (body) and the effects of the external world well enough to predict accommodations to future events
- -Example: Predict the weight of a full cup of water
Anticipatory Mechanisms (Hoark application to balance)
Feed-forward balance (Anticipatory):
- Anticipatory postural control
- Postural responses are made prior to voluntary movement that is potentially destabilizing in order to maintain stability during the movement
- Example: trunk reactions before reach
As compared to Feedback balance (Reactive):
- Compensatory or reactive postural responses
- Sensory feedback from unexpected external perturbations triggers postural responses
We need to be able to do BOTH
Systems Model (Horak): Behavioral Goals (Task)
- Therapists need to appreciate the powerful organizing influence of goals/tasks and use them to their advantage
- Example: Pick up a glass to fill it with water versus pick a glass to put it in the dishwasher
Systems Model (Horak): Environmental Adaptation (Environment)
The environment places constraints on movement strategies by determining the physical conditions under which movements are carried out
-Therapist’s responsibility to teach patients the process of successful adaptation
Individual Sensory Systems & Strategies (Horak added this to Balance/Posture Systems model)
- Vision: ability to maintain balance in…well lite environments, in the dark and in the presence of stationary and moving objects
- Sensory: ankle proprioception and surface sensation
Sensory Strategies (Horak)
- When a sense is not providing optimal or accurate information, less “weight” is given to that sense and greater “weight” is given to the more accurate senses
- Ex: walking in the dark rely less on vision and more on sensation on bottom of foot and ankle.foot proprioception
- -pt with decreased tactile acuity and proprioception due to diabetes relies more on vision
Test the 3 Sensory Systems
- Foam and Dome
- Balance Master
- Equitest
Clinical Test for Sensory Interaction in Balance (CTSIB)
- Vision
- Proprioception/sensation
- Vestibular
Foam and Dome
(CTSIB)
Test
Test: Vision, Sensation of the feet/ankles, and Vestibular
Clinical version of Equitest
Look at postural sway
Foam-diminish ankle proprioception and feet sensation
Manipulate vision and sensation
Balance Master
Can be used as an eval tool
Follows COP on force plate – see how skewed it is
Equitest
Visual cover moves with platform , so entire visual field is moving
For Eval
Rules for testing the sensory system
- Pts need to actively explore the movement possibilities through trial and error
- Initial performance may be quite poor as pts explore and find their own movement solutions
- PTs need to stress the importance of generating multiple movement solutions to any given task
