Coordinaiton S2W5

Question 1

definition of coordination (Oxford English Dictionary)

Answer 1

“The organisation of the different elements of a complex body or activity so as to enable them to work together effectively”

Question 2

definition of coordination (van Emmerick et al. quoting Turvey, 1990)

Answer 2

“Coordination involves bringing together the degrees of freedom at each level (e.g. motor units, muscles, segment, joints) into proper relations”

Question 3

initiating movement: pulling on desk

Answer 3

• leg muscles (gastrocnemius( switches on first to fixate the body - need solid base to pull against
• biceps can’t work effectively unless we coordinate the legs to create a stable base

Question 4

anticipatory postural adjustments

Answer 4

• putting the body in a good position to be able to carry out the task

Question 5

reaction time tests to look at anticipatory postural adjustments

Answer 5

Method:
- various reaction time tests whilst measuring EMG in muscles involved

Results

• we have a proximal to distal sequencing of the muscles switching on - due to transmission time of the signal but goes beyond this
• but when we don’t need to stabilise the joints (e.g. sensor we have to press and arm are resting on table), we don’t see the proximal to distal sequencing

Question 6

angle during single joint movement

Answer 6

• joint angles changing follow an S-shaped curve

- initially not moving, then quick movement, then not moving again

Question 7

velocity during single joint movement

Answer 7

• velocity is the speed of an object in a particular direction
• if starting still, initial velocity = 0, and velocity = 0 at the end, but speed up and slow down in the middle
• steepest part of curve = highest velocity

Question 8

acceleration during single joint movement

Answer 8

• acceleration is the rate of change of velocity
• acceleration = force x mass
• force = mass x acceleration so forces we are producing will follow a similar pattern
• acceleration to speed arm up (+) and deceleration to slow the arm down (-)

Question 9

agonist-antagonist patterning with elbow extension

Answer 9

• triceps (agonist) switch on to move the arm
• then biceps (antagonist) switch on to slow the arm down
• then some combination of the two at the end
• this is called a triphasic pattern of activity
• remember EMG patterns show when muscles switch on and how active they are - takes time to produce force

Question 10

agonist-antagonist patterning when throwing a heavy medicine ball

Answer 10

• when throwing a light ball arm moves fast so would need lots of biceps activity to slow arm down
• medicine ball is heavy so arm moving slowly so only need small amount of biceps activity to slow arm down

Question 11

(Chowdhary and Challis, 1999) study on release time: Method

Answer 11

• task: throw tents ball at 20cm target 8m away
• arm resting on table so can only extend elbow and wrist
• they created the simulation model which is a mathematical representation of two segments: mass and inertia, and a segment for the wrist
• at each joint had a torque generator
• can determine when to turn elbow on and off and same for wrist
• can look at timing required between those two events and when you need to release ball to still hit target
• carried out twice: 1. to determine fastest and most accurate throw and 2. to determine most robust to 4ms errors (still hits target despite not being timed perfectly)
• trying to determine optimum release time

Question 12

(Chowdhary and Challis, 1999) study on release time: Results

Answer 12

• there was a 49ms delay from switching on elbow to switching on wrist (56ms when robust)
• release time 84.3ms (89.4ms when robust)
• release window - time where ball could have been released and still hit target = 1.2 ms (2.4 ms when robust)
• very small window to be successful

Question 13

define robustness

Answer 13

measurement of tolerance to change in parameters

Question 14

tapping study

Answer 14

Method

• a pressure sensor under each index finger
• 3 conditions:
• left and right simultaneous
• left then right (smallest time we can get between the two?)
• right then left
• 3 groups:
• control
• practice group
• instructed practice

Results

• when we think we’re touching sensors simultaneously there is a mean inter-tapping interval of 5ms
• left then right, best group managed just over 10ms
• right then left best score was 7ms
• can’t time movements very precisely

Question 15

bimanual coordination

Answer 15

brain must simultaneously control multiple movements, such as when we use our two hands to perform a task

Question 16

bimanual coordination task - 2 pens

Answer 16

• 2 pens on table, 1 close, 1 further away
• say go and pick up as fast as possible
• speed-accuracy trade off - if we have to move limb further it will take more time to pick the pen up

based on Fitt’s law:

• pen far away has largest index of difficulty
• pen far away should have largest movement time
• when you try to pick up both pens at the same time the closer hand slows down
• typically when the two arms are working together, they don’t have exactly the same movement pattern (pens may not be picked up at exactly the same time) but the time at which both hands reach their peak height is coordinated

Question 17

explain how bimanual coordination can be an advantage

Answer 17

• motor equivalence - e.g. when writing forwards with dominant hand and mirroring with other hand, it makes writing with other hand easier due to bimanual coordination
• bimanual coordination makes some tasks easier so can be an advantage

Question 18

explain how bimanual coordination can be a disadvantage

Answer 18

• e.g. moving foot clockwise and then with hand write number 6 in air
• foot then starts moving anti-clockwise
• easier to move them in the same way
• bimanual coordination is a disadvantage for some tasks when you want to move each limb independently e.g. drumming

Question 19

define variability

Answer 19

“Every time we replicate the same movement, a certain amount of change may be recorded between its subsequent repetitions” (Preatoni et al., 2012)

Question 20

variability - noise - writing name example

Answer 20

• if you write your name
• then put pen back on paper exactly where you started, and write name again
• do this 10 times
• there won’t be a single one that lies exactly on top of the others
• always going to be a small deviation as there is noise in the signals we produce in the motor system

Question 21

two types of variability: 1) increasing the degrees of freedom

Answer 21

• beginner –> freeze the degrees of freedom to simplify it and control the movement with one joint
• expert –> unfreeze the joint = more variability in movement

Question 22

two types of variability: 2) kinematic movement variations

Answer 22

• If we’ve got a certain technique we use and do lots of trials we find none of those trials look identical - always some variation which can be due to these things:
• there is always some noise from the motor system
• conscious feedback corrections
• planning error - sometimes our movements look different because we plan them slightly differently