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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
SURFACE or indwelling: cannot measure deep muscles
surface
26
SURFACE or indwelling: can record deep muscles
indwelling
27
explain the placement, invasion, isolation and measurement of the surface electrode method
1) placed on the skin 2) non invasive and easy to apply 3) harder to isolate individial muscles 4) cannot measure deep muscles
28
explain the placement, invasion, isolation and measurement of the indwelling electrode method
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
which has a. smaller recording area, surface or indwelling
indwelling
30
true or false: the emg record potential difference between electrodes
true
31
what are the 4 things you can determine from EMG
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
how can we measure when a muscle is active during an emg
equipment registers a change in voltage
33
what spefically can we determine about when a muscle is active
timing of activation duration
34
how can we compare muscle activation during differen tasks using EMG
compare the amplitudes between recordings
35
how can we determine when muscles are /arent working together
by comparing the EMG traces of multiple muscles
36
how can we determine how hard (relative to a maximal contraction) a muscle is working
by normalizing the EMG traces to a maximum voluntary isometric contraction
37
what does MVIC stand for
maximum voluntary isometric contraction
38
what is maximum voluntary isometric contraction
the maximum force a subject can deliberatly generate during a static (isometric) cotnraction
39
what is a common and population method of amplitude normalizing EMG data
maximum voluntary isometric contraction (MVIC)
40
MVIC is assumed equatable to what
maximum innervation
41
how do youcalculate percent MVIC
get MVIC (from isometric contraction in mV) get max mV during activity %MVIC =Max activty/MVIC * 100
42
what are the 3 functions of amplitude normalization
to format in a standardized manner to make consistent to place in a comparable context
43
what are the benefits of amplitude normalization
eliminate influence of detection condition (impedence to signal, electrode location) provide a scale for data
44
what are the critisism of amplitude normalization
can the patient actially contact to 100% what type of exercise (is it relevant to activity)
45
what are the 3 things EMG cannot determine
1) which muscle (of two) is working harder 2) amount of force a muscle produces 3) number of active motor units
46
CAN or cannot determine: number of active motor units
cannot
47
CAN or cannot determine: amount of force a muscle produces
cannot
48
CAN or cannot determine: which muscle (of two) is working harder
cannot
49
CAN or cannot determine: when is muscle is active
can
50
CAN or cannot determine: compare muscle activation during different tasks
can
51
CAN or cannot determine: when muscles are (or arent) working together
can
52
CAN or cannot determine: how hard (relative to a maximum contraction) a muscle is working
can
53
why can we not determine which muscle (of two) is working harder
because muscles vary in size and function (greater activtiy does not necerailly mean greater force)
54
true or false: (greater activtiy does not necerailly mean greater force)
true
55
explain why we cannot determine the amount of force a muscle produced from EMG
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
does Emg measure force?
no it measures level of activity, not force
57
what are the too many unknown variables that make it so that you cannot measure the force a muscle produces
1) no way of knowing # of activated fibers 2) how much force a fiber contributes 3) not necesarily measuring all active fibers
58
why can we not determine the number of active motor units
some active fibers are not accessible to equipment (too deep)
59
what are the 2 EMG limitations
signal amplitude is inversly proportional to distance crosstalk
60
explain crosstalk
electrodes over an adjacent muscle pick-up a signal via skin conduction
61
what reduces amplitude that is not distance,
incrased body fat
62
true or false and explain: difficult to record deep fibers/muscles
true because signal amplitude is inversely proportional to distance
63
what are the 4 guidelines for skin preperation
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
true or false: the electrodue is positioned parallel or perpendicular to muscle fibers
parallel
65
the electrode should be placed along what midline
longitudinal midline
66
true or false and why: the electrode can be placed at midline or muscle edge
false, do not place at muscle edge because it may pick up adjacent muscle signal
67
why can you not place the electrode near the tendon
thinner and fewer fibers

POTH 225: BIOMECHANICS (15 decks)

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