Response Programming

What is an open loop?

The output has no influence on the control action (no time for feedback)

When is an open loop used?

During rapid movements

What is a closed loop?

An open loop system which contains feedback loops

When are closed loops used?

Slow, time consuming tasks

What does the open loop control involve?

Stimulus identification > Response selection > Response programming

The executive (brain) sends a signal to the effector (muscles) which carries out the movement

What is a motor programme?

An abstract that when initiated results in the production of a coordinated movement sequence

What is the order of a motor programme?

Motor programme > Motor neuron > Muscle

What are the 3 pieces of evidence for motor programmes?

• Reaction times

• Deafferentation studies

• EMG studies

How does reaction times support the motor programme theory?

As a task gets more complex, reaction times are slower

More steps > More preparation > Slower reaction time

How does deafferentation studies support the motor programme theory?

When efferent nerves are removed, movement can still be produced

This proves that the motor programme is stored and feedback isn’t required

Explain the cat deafferentation study?

Cats had a mid-brain cut and they put it on a treadmill. The cats legs drag across the treadmill

However when the spine is electrically stimulated the cats legs start to walk, proving that the cats spine has pattern generators which once turned on will switch on and off different circuits to carry out the movement, e.g. walking

How does EMG studies support the motor programme theory (Elbow extension study)?

• During an antagonistic muscle pair study, the antagonist will show electrical movement towards the end as it acts as a break

• When the antagonist was blocked, the reading still ahd electrical movement. This shows it’s a pre-programmed movement sent in advance to the muscle

• However these tests were done under rapid movement. When done under slow movement the athlete had time to override the motor programme

When must a stop signal be provided for a task?

The EMG elbow extension study found that the stop signal must be around 100m/s after the go signal for the whole motor programme to not be completed

What are problems with motor programmes?

Storage = the brain would need a seperate motor programme for every movement

Novelty = the brain doesn’t have a motor programme for new movements

Degrees of freedom = many muscles can move in multiple ways to achieve the same goal

What is a Generalised Motor Programme (GMP)?

A motor programme whose expressions can be varied depending on the choice of parameters

What are the 3 invariant features of a GMP?

• Order of events

• Relative timing

• Relative force

Explain the order of events of a GMP

A modified programme will still have the same order of the sequence that the skill usually has

Explain the relative timing of a GMP

• A study asked for a taekwondo kick as quick as possible and at 80%

• When the timings were overlayed, the parts of the skill were sped up proportionately rather than certain parts of the skill

Explain the relative force of a GMP

When a force is needed to increase, all the muscles will increase at a proportionate level, not just certain muscles

What are the 3 changeable factors of a GMP?

• Overall duration

• Overall force

• Muscle selection

Explain the overall duration of a GMP

The GMP will have constant order of events and relative timing, but the duration of the skill can be sped up or slowed down

Explain the overall force of a GMP

The relative force of a GMP is constant, but the overall force will adjust to the demands of the task

E.g. throwing a 5kg ball will require a larger overall force than a normal basketball

Explain muscle selection for a GMP

The athlete must decide the appropriate muscles to use for a motor programme

E.g. using a different muscle for different bowls in cricket

Explain the closed loop control diagram

• Reference of correctness = predicting what the movement should feel like

• Feedback = this is received from the motor programme. this will be compared to the reference of correctness

What is feedforward?

• Athlete predicts the movement and selects the correct GMP before acting.

• Executes the action without waiting for feedback.

• Compares expected feeling of the movement to the actual sensory feedback afterwards to evaluate performance.

What is the reflexive closed loop control study?

• A study on keeping elbow flexion at 90 degrees

• A person will only produce a certain force level for this.

• However when an unexpected increase in weight occurs the person will drop their arm because the force produced was insufficient.

• Then the participant will return their arm to 90 degrees by increasing their force output

Explain the monosynaptic stretch reflex 1 (M1)

• After 30 ms of the weight being added there is a small muscular activity

• This is due to muscle fibres in the bicep stretching

• Muscle spindles then send signals to the spinal cord which activates the bicep motor neurons

• This causes the muscle to contract automatically

Explain the triggered/long loop response reflex (M2)

• After 50-80 ms of the weight being added, the muscle spindles send information up the spine into the brain

• This triggers a pre-programmed response

• This is still an unconscious process

t

Explain the voluntary reflex (M3)

• After 120 ms of the weight being added

• Information has entered the stages of information processing