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Physical Agents II > Biofeedback > Flashcards

Biofeedback Flashcards

1
Q

What is electromyographic feedback?

A

A training technique that enables an individual to gain some element of voluntary control over muscular or autonomic nervous system functions using a device that produces an auditory or visual stimuli

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2
Q

what is the functional unit of a muscle

A

motor unit

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3
Q

what is a motor unit comprised of

A

a single alpha motor neuron and all of the fibers it innervates

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4
Q

when do muscle fibers contract

A

when the action potential of the motor nerve which supplies them reaches a depolarization threshold

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5
Q

what does depolarization generate?

A

an electromagnetic field and the potential can be measured as microvolts

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6
Q

How does all of that tell the measuring device what is happening?

A
  • The depolarization, which spreads along the membrane of the muscle, is the muscle action potential (AP).
  • The MUAP is the summation of the individual muscle APs for all of the fibers of a single MU
  • Therefore, the EMG signal is the algebraic summation of the MUAPs within the “pick-up” area of the electrode being used. These signals are picked up, amplified, and translated into audible-visible-or both readings
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7
Q

Which units are picked up first

A

smaller units first, larger units if we need them

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8
Q

can you read more with a larger or smaller contraction?

A

larger because we can only read what is directly under the electrode field

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9
Q

Does EMG measure force output?

A

no no no
- just because you are getting higher feedback it does not mean that you are stronger

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10
Q

what might reconditioned individuals display?

A
  • higher levels of EMG activity to exert the same amount of force as exerted by non- deconditioned individuals
  • people who are trained are more efficient in using the MUs
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11
Q

What can affect an EMG signal?

A

fatigue

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12
Q

muscle comprised of predominately one fiber type may have….

A
  • more of a linear relationship under isometric non-fatiguing condition
  • Mixed fiber types are more curvilinear
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13
Q

EMG amplitudes are greater for which type of contractions?

A
  • concentric amplitudes are greater than eccentric contractions when lifting or letting down the same load (length- tension issues and force velocity issues)
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14
Q

is EMG/Biofeedback a monitor or a measure?

A

monitor
* Most devices use some type of analog meter to demonstrate activity. Some meters have objective numbers and others do not

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15
Q

Why is EMG information difficult to compare session to session?

A
  • Electrode placement
  • Skin impedance
  • Extraneous noise
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16
Q

how can you “normalize” EMG activity to compare performance between sessions?

A
  • by looking at the % of change within each session
  • Some elite devices will do this for you
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17
Q

Indications for use of biofeedback

A
  • Decrease unwanted muscle contraction
  • Promote muscle contractions
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18
Q

what should biofeedback be?

A

TASK SPECIFIC

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19
Q

Goals of intervention

A
  • Improve muscle performance
  • Reduce pain
  • Increase ability to perform functional tasks
  • Improve joint integrity and mobility
  • Reduce complications of injury
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20
Q

Active Electrode

A

has built in amplifiers

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21
Q

what are passive electrodes made of

A
  • silver silver chloride
  • gold based
22
Q

what do passive electrodes utilize

A

bipolar electrode placement where there is a pair of recording electrodes and a reference (or ground) electrode

23
Q

Since there is no built in amplifier with passive electrodes, what do you gotta do

A

reduce skin resistance as much as possible before recording

24
Q

ground electrode

A

 Helps the EMG unit discriminate the muscle activity under the recording electrodes from the noise or extraneous activity

25
Q

Electrode size

A

 Choose size based on desired recording area
 Too large = unwanted noise from adjacent muscles
 Too small = not enough sampling –> decreased feedback

26
Q

Electrode placement

A

 Ground electrode should be on a bony prominence if available (some differing information on this)
 Recording electrodes need to run parallel to the muscle fibers

27
Q

Inter- electrode distance: closer together

A

more specific information, but limits the recording area (good to start muscle relaxation programs here and then widen them as the patient progresses)

28
Q

Inter-electrode distance: further apart

A

gather more data, but may have increased noise from adjacent muscles (good to begin muscle recruitment program here and then narrow them as the patient progresses)

29
Q

Purpose of amplifier

A
  1. Increase the amplitude of the signal
  2. Units have “gain” (sensitivity) adjustments that range from 0-10 to 0-100 microvolts
30
Q

Differential Amplifiers

A
  • Determine what is noise by looking
    at what is common between the two recording electrodes
  • It discounts the noise and enhances the signals that are different
31
Q

Greater amplification =

A

greater sensitivity

32
Q

higher sensitivity (high gain) runs in what range?

A

1-10 microvolts and convey information about small changes in EMG activity

33
Q

Low sensitivity (low gain) run in what rage?

A

0-100 microvolts and conveys larger changes in EMG activity

34
Q

What does filtering aid in

A

elimination of unwanted electrical signals (noise)

35
Q

what frequency do movement artifacts occur?

A

range of < 100 Hz

36
Q

Most electrical noise is found at what frequencies?

A
  • high
    > 100 Hz
37
Q

What frequency do most EMG signals fall in the range of?

A

100-1000 Hz
- A filter can be used to narrow this range and only read frequencies occurring at 100- 500Hz

38
Q

What is a disadvantage of filtering

A

loss of some EMG activity

39
Q

Rectification

A

is taking the positive and negative values of a signal and making them all positive (full-wave rectification) or just eliminating all of the negative values (half-wave rectification)

40
Q

Integration

A
  • An averaging of the signal
  • Rather than displaying every point of a rectified signal an average of every 6 data points of sEMG
    activity is plotted
  • This gives you a “smoother” line
41
Q

What types of feedback are there?

A

visual and auditory

42
Q

what should you consider when choosing the type of feedback

A

Patient’s age
Preference
Type of desired muscle activity
Stage of training

43
Q

Time Constraints

A
  • pick up how much integration you are doing
  • the time the resistor compact circuit takes to discharge stored signal
  • the shorter the time constant the more info you pick up
44
Q

what is the time constant recommendation for muscle recruitment

A

0.3 seconds

45
Q

Threshold

A

 Set threshold level based on desired activity
 When the EMG signal reaches this threshold, a threshold detector will either turn on or turn off the feedback
 Also consider the intensity of the feedback (how loud, etc.)

46
Q

Skin Impedance

A

Essential to reduce impedance as much as possible

47
Q

Muscle Recruitment

A

 Patient must have some (minimal) ability to perform a voluntary contraction.
 Electrode size to suit the size of the muscle
 Begin with a wider placement progressing to a narrower placement if needed
 Begin with a high sensitivity level and progress to a lower sensitivity level
 Preferable time constant around 0.3 seconds
 Set threshold just above level of resting activity (baseline) and progress up
 Decide on nature and frequency of feedback

48
Q

deciding on nature and frequency of feedback

A

 Concurrent feedback vs. knowledge of results
 May progress from frequent to intermittent feedback
 Too much feedback may lead to dependence and limit learning

49
Q

Muscle Inhibition

A

 Select electrode size appropriate for size of muscle being targeted
 Inter-electrode distance should begin small and widen with progress
 Initiate sensitivity appropriate to level of activity
 Longer time constant initially
 Set threshold just below baseline level of activity and progress by lowering it

50
Q

Documentation should include:

A

 Nature of Rx (muscle recruitment vs. inhibition)  Activities performed (remember to make it functional)
 Muscle(s) targeted
 Electrode type and size
 Electrode placement including inter-electrode distance
 Unit settings (sensitivity, threshold)
 Feedback type
 Duration or number of repetitions

Physical Agents II (8 decks)

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