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POTH 225: BIOMECHANICS > lab 7: EMG > Flashcards

lab 7: EMG Flashcards

1
Q

what does EMG stand for

A

electromyography

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2
Q

what does EMG
measure

A

measuring elecrtical signals from muscles

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3
Q

what are the 4 reasons EMG is used

A

1) studying the effects of faitgue and work stress on muscle function

2) analyzing how muscle activation changes with different movement parametes, disease or treatments

3) diagnosing muscle dysfunction or neuromuscular disorders

4) understanding CNS organization in coordinated movement

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4
Q

true or false: the voltage gradient across the muscle fiber membrane is about what mV

A

90 mV

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5
Q

why is there a voltage gradient across the muscle fiber gradient

A

due to distrubition of sodium, potassium and chloride

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6
Q

the voltage graidne tis due to a distribution of what 3 ions

A

sodium
potassium
chloride

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7
Q

when is action potential generated for muscle physiology

A

when muscle fiber depolarized by 10 mv

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8
Q

action potentioal is generated when muscle fiber depolarized by BLANK

A

10 mv

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9
Q

WHERE does action potential begin

A

at neuromuscular junction

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10
Q

action potential is due to exchange of what

A

sodium and potassium ions

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11
Q

true or false: action potential proceeds along the muscle fiber in only 1 directino

A

false, in both directions

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12
Q

what is a motor unit

A

single motor neuron and all the muscle fibers it innervates

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13
Q

EMG consists of the sum of electrical activity from what

A

numerous motor units within the detection region

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14
Q

do EMG constic of the sum of electrical activtiy from numerous or a single motor unit within the detection region

A

numerous

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15
Q

true or false: motor neurons closer to skin surface hve a stronger signal

A

true

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16
Q

motor neurons closer or further to skin surface hve a stronger signal

A

closer

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17
Q

what are the basic system components of instrumentation of EMG

A

differential electrodes
ground electrode
amplifier and analogy to digital converted
strorage/display unit

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18
Q

SURFACE or indwelling: placed on the skin

A

surface

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19
Q

SURFACE or indwelling: inserted thru skin into muscle

A

indwelling

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20
Q

SURFACE or indwelling: non invasive, easy to apply

A

surface

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21
Q

SURFACE or indwelling: invasive (sterile) requires more skill

A

indwelling

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22
Q

SURFACE or indwelling: harder to isolate individual muscles

A

surface

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23
Q

SURFACE or indwelling: can isolate individual muscles/motor units -small recording area

A

indwelling

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24
Q

SURFACE or indwelling: cannot measure deep muscles

A

surface

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25
Q

SURFACE or indwelling: cannot measure deep muscles

A

surface

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26
Q

SURFACE or indwelling: can record deep muscles

A

indwelling

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27
Q

explain the placement, invasion, isolation and measurement of the surface electrode method

A

1) placed on the skin
2) non invasive and easy to apply
3) harder to isolate individial muscles
4) cannot measure deep muscles

28
Q

explain the placement, invasion, isolation and measurement of the indwelling electrode method

A

1) inserted thorugh skin into muscle
2) invasive, requires more skinn
3) can isolate indivudal muscles/motor units (small recording area)
4) can record deep muscles

29
Q

which has a. smaller recording area, surface or indwelling

A

indwelling

30
Q

true or false: the emg record potential difference between electrodes

A

true

31
Q

what are the 4 things you can determine from EMG

A

1) when a muscle is active
2) compare muscle activation during different tasks
3) when muscles are (or arent) working together
4) how hard (relative to a maximal contaction) a muscle is working

32
Q

how can we measure when a muscle is active during an emg

A

equipment registers a change in voltage

33
Q

what spefically can we determine about when a muscle is active

A

timing of activation
duration

34
Q

how can we compare muscle activation during differen tasks using EMG

A

compare the amplitudes between recordings

35
Q

how can we determine when muscles are /arent working together

A

by comparing the EMG traces of multiple muscles

36
Q

how can we determine how hard (relative to a maximal contraction) a muscle is working

A

by normalizing the EMG traces to a maximum voluntary isometric contraction

37
Q

what does MVIC stand for

A

maximum voluntary isometric contraction

38
Q

what is maximum voluntary isometric contraction

A

the maximum force a subject can deliberatly generate during a static (isometric) cotnraction

39
Q

what is a common and population method of amplitude normalizing EMG data

A

maximum voluntary isometric contraction (MVIC)

40
Q

MVIC is assumed equatable to what

A

maximum innervation

41
Q

how do youcalculate percent MVIC

A

get MVIC (from isometric contraction in mV)
get max mV during activity

%MVIC =Max activty/MVIC
* 100

42
Q

what are the 3 functions of amplitude normalization

A

to format in a standardized manner
to make consistent
to place in a comparable context

43
Q

what are the benefits of amplitude normalization

A

eliminate influence of detection condition (impedence to signal, electrode location)
provide a scale for data

44
Q

what are the critisism of amplitude normalization

A

can the patient actially contact to 100%
what type of exercise (is it relevant to activity)

45
Q

what are the 3 things EMG cannot determine

A

1) which muscle (of two) is working harder
2) amount of force a muscle produces
3) number of active motor units

46
Q

CAN or cannot determine: number of active motor units

A

cannot

47
Q

CAN or cannot determine: amount of force a muscle produces

A

cannot

48
Q

CAN or cannot determine: which muscle (of two) is working harder

A

cannot

49
Q

CAN or cannot determine: when is muscle is active

A

can

50
Q

CAN or cannot determine: compare muscle activation during different tasks

A

can

51
Q

CAN or cannot determine: when muscles are (or arent) working together

A

can

52
Q

CAN or cannot determine: how hard (relative to a maximum contraction) a muscle is working

A

can

53
Q

why can we not determine which muscle (of two) is working harder

A

because muscles vary in size and function
(greater activtiy does not necerailly mean greater force)

54
Q

true or false: (greater activtiy does not necerailly mean greater force)

A

true

55
Q

explain why we cannot determine the amount of force a muscle produced from EMG

A

too many unknown variables
1) no way of knowing # of activated fibers
2) how much force a fiber contributes
3) not necesarily measuring all active fibers

56
Q

does Emg measure force?

A

no it measures level of activity, not force

57
Q

what are the too many unknown variables that make it so that you cannot measure the force a muscle produces

A

1) no way of knowing # of activated fibers
2) how much force a fiber contributes
3) not necesarily measuring all active fibers

58
Q

why can we not determine the number of active motor units

A

some active fibers are not accessible to equipment (too deep)

59
Q

what are the 2 EMG limitations

A

signal amplitude is inversly proportional to distance
crosstalk

60
Q

explain crosstalk

A

electrodes over an adjacent muscle pick-up a signal via skin conduction

61
Q

what reduces amplitude that is not distance,

A

incrased body fat

62
Q

true or false and explain: difficult to record deep fibers/muscles

A

true because signal amplitude is inversely proportional to distance

63
Q

what are the 4 guidelines for skin preperation

A

1) mark the location of the electrode
2) shave the area over the muscle
3) clean the area with rubbing alcohol
4) apply the electrode only after the alcohol evaporates

64
Q

true or false: the electrodue is positioned parallel or perpendicular to muscle fibers

A

parallel

65
Q

the electrode should be placed along what midline

A

longitudinal midline

66
Q

true or false and why: the electrode can be placed at midline or muscle edge

A

false, do not place at muscle edge because it may pick up adjacent muscle signal

67
Q

why can you not place the electrode near the tendon

A

thinner and fewer fibers

POTH 225: BIOMECHANICS (15 decks)

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