Performance And Motor Control Characteristics Of Functional Skills

Question 1

Centre of mass (COM)

Answer 1

Weighted average of all segments in body, the body’s balance point

Question 2

Centre of pressure (COP)

Answer 2

Point location of the vertical ground reaction force

Question 3

Base of support (BOS)

Answer 3

The area defined by contact with a support surface
Area beneath an object or person that includes every point of contact that makes with supporting surface

Question 4

Margin of stability (MOS)

Answer 4

Distance between the COM position and the edge of the BOS

Question 5

Equation for COM

Answer 5

Com= mi x ri / mi
MiRi = sum of segment masses x distance from reference
Mi= total mass

Question 6

COP equation

Answer 6

COPx = Momentx / FORCEvertical
- average of pressures over the surface in contact with ground

Question 7

What are examples of base of support

Answer 7

Body parts, feet or hands, or crutches, or chair person sitting on

Question 8

To remain standing balance what must happen

Answer 8

COM must remain within the BOS

Question 9

During standing what happens

Answer 9

COP acts to control the COM and keep it within the BOS

Question 10

What happens if the COM moves outside the BOS

Answer 10

BOS must be changes quickly to “catch” the COM or a fall will occur

Question 11

How to maintain dynamic balance (walking balance)

Answer 11

BOS must change to control COM movement

Question 12

Summary of balance control

Answer 12

To prevent fall, COM stays within BOS or projected into a forthcoming BOS
COP helps control the COM

Question 13

How can stability be assessed

Answer 13

Measuring the margin of stability (MOS)

Question 14

What is involved in control of locomotion (gait)

Answer 14

Central pattern generators (CPG) in spinal cord

Question 15

What is CPG in spinal cord provide

Answer 15

Basis for stereotypic rhythmicity of walking and running gait patterns (include arm swing)

Question 16

What else influences gait

Answer 16

Proprioceptive feedback from muscle spindles and GTOS
- timing of locomotive cycle
- size of muscle response

Question 17

How do CPGs work

Answer 17

• Motor signal from higher brain structures to CPG in spinal cord to extensors and flexors
• Proprioception from flexors and extensors to CPG in spinal cord to higher brain structures

Question 18

What is the rhythmic structure of locomotion

Answer 18

• components of a step cycle
• rhythmic relationship between arms and legs
• pelvis and thorax relationship during walking

Question 19

What is the relationship between pelvis and thorax during walking

Answer 19

In at slow speeds
Out at higher speeds

Question 20

What is the practical benefit of analyzing rhythmic structure of gait patterns

Answer 20

Allows for assessment of coordination problems of trunk and legs (ex Parkinson’s disease)

Question 21

What is another important motor control characteristic of locomotion

Answer 21

• head stability
  Vestibular canals and vision both based in head

Question 22

What happens at critical speed

Answer 22

People spontaneously change from walking to running gait and vice versa

Question 23

Why do spontaneous gait transitions occur

Answer 23

Most popular hypothesis: minimize metabolic energy use

Question 24

When walking or running what is vision important for

Answer 24

Enabling us to contact objects and avoiding contact with objects

Question 25

What vision control system is responsible for contacting objects

Answer 25

Tau (time to contact)

Question 26

How does vision help with avoiding contact with objects

Answer 26

- provides advanced info to determine how to avoid contact - step over, dodge - provides body scaled info to determine how to walk through door, to step on a step

Question 27

What is the speed-accuracy trade off

Answer 27

When both speed and accuracy are essential to perform a skill

Question 28

When speed is emphasized

Answer 28

Accuracy is reduced

Question 29

When accuracy is emphasized

Answer 29

Speed is reduced

Question 30

Fitt’s law

Answer 30

Most significant laws associated with human movement Mathematically predict movement time for speed accuracy skills

Question 31

What do we need to know for Fitt’s law

Answer 31

Spatial dimensions of 2 variables Movement distance Target size

Question 32

What else can be calculated base on Fitts law

Answer 32

Index of difficulty

Question 33

What is index of difficulty

Answer 33

Quantitative measure of the difficulty of performing a skill involving both speed and accuracy requirements

Question 34

Speed-accuracy skills: Fitts law

Answer 34

As target size becomes smaller or as distance gets longer, the movement speed will decrease in order for accurate movement

Question 35

Open loop

Answer 35

- does not use feedback - initial speed, direction, accuracy under CNS control - at movement initiation, initial movement instructions are sufficient to move limb to vicinity of target - efferent info only (eg. Basketball freethrow)

Question 36

Closed loop

Answer 36

- does use feedback - control center send only enough info to effectors to initiate movement - relies on feedback to continue and adjust if needed (eg. Dribbling a basketball)

Question 37

What 2 motor control processes underlie performance of speed-accuracy skills

Answer 37

Open loop control Closed loop control

Question 38

Where is accuracy for closed loop control

Answer 38

At termination of movement

Question 39

What does Closed loop feedback need to hit target accurately

Answer 39

From vision and proprioception needed at end of movement to ensure hitting target accurately

Question 40

What is important in closed loop control

Answer 40

Whether person has time to make necessary corrections as limb nears the target

Question 41

What is the third phase proposed

Answer 41

Movement preparation phase

Question 42

Movement prep phase

Answer 42

Person uses vision to determine the regulatory conditions that characterize the environmental context in which action will occur

Question 43

Prehension

Answer 43

Reaching for and grasping an object

Question 44

3 distinct components of prehension

Answer 44

1. Transport 2. Grasp 3. Object manipulation

Question 45

Transport

Answer 45

Movement of hand to object

Question 46

Grasp

Answer 46

Hand taking hold of object

Question 47

Object manipulation

Answer 47

Functional goal of prehension - makes pretensions different from reaching and pointing - influences characteristics of transport and grasp

Question 48

What does prehension demonstrate

Answer 48

Speed accuracy trade-off - during transport phase, arm will accelerate and then decelerate - as object size decreases, length of deceleration phase increases (longer to reach target)

Question 49

Biannual coordination skills

Answer 49

Motor skills that require simultaneous use of two arms

Question 50

What may biannual coordination skills require

Answer 50

Arms to move with same or different spatial and/or temporal characteristics

Question 51

Two types of biannual coordination skills

Answer 51

Symmetrical biannual coordination (clapping, lifting, rowing a boat) Asymmetrical biannual coordination (playing musical instrument, patting head and rubbing stomach)

Question 52

What are motor control characteristics related to biannual coordination

Answer 52

The two arms prefer to perform symmetrically

Question 53

Three phases of catching a moving object

Answer 53

1. Initial positioning of arm and hand 2. Shaping of hand and fingers 3. Grasping the object

Question 54

Two critical time periods in visual contact time needed to catch a moving object

Answer 54

Initial flight Just prior to hand contact

Question 55

What visual contact is needed between the two critical periods

Answer 55

Brief, intermittent visual snapshots sufficient to make contact

Question 56

Ball speed effect

Answer 56

Skilled strikers demonstrate similar bat movement time for all ball speeds

Question 57

What visual contact with moving ball do skilled strikers do

Answer 57

Do not maintain throughout ball flight but visually “jump” from early flight to predicted location in area to strike ball - head stability important