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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
Electrode size
 Choose size based on desired recording area  Too large = unwanted noise from adjacent muscles  Too small = not enough sampling --> decreased feedback
26
Electrode placement
 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
Inter- electrode distance: closer together
more specific information, but limits the recording area (good to start muscle relaxation programs here and then widen them as the patient progresses)
28
Inter-electrode distance: further apart
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
Purpose of amplifier
1. Increase the amplitude of the signal 2. Units have “gain” (sensitivity) adjustments that range from 0-10 to 0-100 microvolts
30
Differential Amplifiers
- 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
Greater amplification =
greater sensitivity
32
higher sensitivity (high gain) runs in what range?
1-10 microvolts and convey information about small changes in EMG activity
33
Low sensitivity (low gain) run in what rage?
0-100 microvolts and conveys larger changes in EMG activity
34
What does filtering aid in
elimination of unwanted electrical signals (noise)
35
what frequency do movement artifacts occur?
range of < 100 Hz
36
Most electrical noise is found at what frequencies?
- high > 100 Hz
37
What frequency do most EMG signals fall in the range of?
100-1000 Hz - A filter can be used to narrow this range and only read frequencies occurring at 100- 500Hz
38
What is a disadvantage of filtering
loss of some EMG activity
39
Rectification
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
Integration
- 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
What types of feedback are there?
visual and auditory
42
what should you consider when choosing the type of feedback
Patient’s age Preference Type of desired muscle activity Stage of training
43
Time Constraints
- 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
what is the time constant recommendation for muscle recruitment
0.3 seconds
45
Threshold
 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
Skin Impedance
Essential to reduce impedance as much as possible
47
Muscle Recruitment
 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
deciding on nature and frequency of feedback
 Concurrent feedback vs. knowledge of results  May progress from frequent to intermittent feedback  Too much feedback may lead to dependence and limit learning
49
Muscle Inhibition
 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
Documentation should include:
 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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