What are some anticipatory postural adjustments?
What do they do?
Recorded the electrical activity in the muscles
- What order do muscles come on
- Found that muscles in legs are activated before the muscles in your arms
- This happens to brace the body for electrical activity(prevents us from pulling ourselves onto the table)
- Stabilises the body
- Stabilising muscles come on first before agonist muscles(creates anticipatory postural adjustments)
What were the differences found in the reaction tests for:
- pushing up
- pushing down
Pushing up:
- A proximal to distal muscle sequencing
- Stabilise body first then carry out the movement
Pushing Down:
- No proximal to distal sequencing
- Arm was on table(no need to stabilise the shoulder and elbow joints)
Define coordination
“Coordination involves bringing together the degrees of freedom at each level (e.g. motor units, muscles, segment, joints) into proper relations” van Emmerick et al. quoting Turvey (1990)
Describe the graphs shown by single joint movements
Most joint actions follow a sigmoid curve
- Tend to move out joints in a rotational nature
- S-shaped - we can work out how quickly it is happening
- Differentiate in respect to time(we can figure out how quickly - velocity - the movement happens)
- Differentiate again - we know when the movement accelerates/decelerates
Describe the triphasic movement pattern(agonist/antagonist)
At what point does the joint physically move
Triphasic patterns(agonist/antagonist) patterns of movement
- This is in isolated joint movement
- Takes time for the muscle to produce enough force
- We are going to get some movement when the antagonist is starting to generate movement
If the ball is heavy that is thrown how does the bicep activity differ?
Bicep activity is nearly lost, as not required
- Coordinated with the activity
- If not required we DO NOT program it
Define:
variability
coordination
- Variability - “Every time we replicate the same movement, a certain amount of change may be recorded between its subsequent repetitions” Preatoni et al. (2012)
- Coordination - “The organisation of the different elements of a complex body or activity so as to enable them to work together” (Oxford dictionary)
What are the 2 types of variability?
- Increasing the degrees of freedom
- Kinematic movement variations
○ Noise from the motor system
○ Feedback corrections (i.e. not noise)
○ Planning errors
What is the difference between outcome variability and execution variability?
- Outcome variability = variability in the result - when it has a positive effect = functional role
- Execution variability = kinematic variability
E.g.: hammer example- Outcome variability can be low despite execution variability
- Therefore not all execution error can be noise or detrimental to performance
- variation in trajectory but not end point
What are the 2 different perspective on movement variability?
Why can variation be helpful?
How does this differ in previously injured people?
Traditional perspective: variation is noise (unwanted)
Dynamical systems: variation has a functional role
* Not all variation is detrimental, but not all is functional - based on observed effect on task - variation is good, those not injured had more variation in their pattern of running ○ Perhaps previously injured people were forced to carry out a certain type of movement to prevent pain - constraint based motor learning
Describe the high bar example of kinematic variation
A novice is likely to have more variation
An expert would have a lower level of variability - more consistent at repeating
SD - in respect to time, and size on hip angle
More expert the person is, the more consistent the gymnast is at recreating the same movement pattern
- When timing is important, experts are better at recreating these movements with less variation
* Mechanically important phases: low variability, 12ms that inputs energy into system --> at bottom * Feedback control adjustments: higher variability, 90 ms much higher than at bottom - At top, gymnast is changing what they are doing in the rotation to control their angular velocity - correcting their technique in each trial (looks wrong in multiple trials) * Moving from novices to experts makes their hand movements more accurate, timing is important to control end angular velocity
Why do experts usually have more variation in their movement pattern?
As you find the correct movement pattern and become more expert, you expect the variation to drop
- Variability increases in experts as they know how to adapt to changes - Technique is more robust to cope with changes in the motor system to create the perfect outcome
Summarise variability
- Outcome variability
- Movement variability
- Dependent on task
- Functional role
Describe what is meant by kinematic variability
- Every time we replicate the same movement there may be variation as we do not have fine-tuned movements
- There is also variation when we are not moving
- There is variation over a small period of time, not able to hold fixed positions
- This is because there is noise within our system
