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Electromyographic
Biofeedback
Chapter 18
© 2004
Purpose
To measure, process,
and feedback biophysical
information
Biofeedback does not
monitor the actual
response itself
It monitors conditions
associated with the
response
© 2004
Types of Biofeedback Units
Electromyographic

Measures electrical activity
in skeletal muscle
Photophlethysmography

Peripheral Temperature



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Measures temperature
changes in distal extremities
Increased temperature
indicates a relaxed state
Decreased temperature
indicates stress, fear, or
anxiety
Measures the amount of light
reflected by subcutaneous
tissue based on the amount of
blood flow
Galvanic skin response


Measures electrical resistance
in the skin
Moist skin conducts a current
better than dry skin
EMG
Detects the amount of electrical activity
associated with a muscle contraction


converts it to visual and/or auditory feedback
promotes strength of the muscular
contraction or facilitates relaxation
Can be used to create a game-like,
competitive atmosphere to motivate
rehabilitation
© 2004
Biophysical Processes and
Electrical Integration
EMG biofeedback measurements vary
between brands
Electrical activity within the muscle increases as
more motor units are recruited
These signals are picked up by electrodes, amplified,
and converted into visual or auditory signals
Electrode placement, superficial vs. deep muscles,
electromagnetic noise, and tissue variability cause
variability in the signals produced
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Electrodes
“Active” Electrodes
Detect electrical signal
“Reference” Electrode
Filters nonmeaningful information
Basic units have one channel composed
of three surface electrodes on a selfadhesive electrode
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The Process
Identify Signal
Get the eletromyographic signal from the
body
Amplify Signal
Filter out background noise
Similar to a volume control on a radio,
enhance the strength of the signal to
meaningful levels
Rectify Signal
Make all values “positive”
Integrate Signal
Group the data into meaningful
clusters
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Indications
Facilitate muscle contractions
Regain neuromuscular control
Decrease muscle spasm
Promote relaxation
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Effects
Purpose: reestablish
sensory-motor loops
‘forgotten’ by patient
Used to facilitate increased
or decreased levels of
motor unit activation
Sound/visual cues
stimulate brain along with
watching the muscle
contract assists in
reopening a neural loop
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Neuromuscular Effects
The cognitive process attempts to inhibit
pathways for relaxation
The goal is to decrease the number of
motor impulses being relayed to the
muscle in spasm
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Pain Reduction
Purpose: restore normal function of the
body part
Facilitating reduction of muscle spasm
reduces the amount of mechanical
pressure placed on nociceptors
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Contraindications
General Rule: If the patient is prohibited
from moving the joint or isometric
contractions, then EMG should NOT be
used
Unhealed tendon grafts
Avulsed tendons
Third degree tears of muscle fibers
Unstable fracture
Injury to joint structure, ligaments, capsule,
or articulating surface
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Clinical Application
Biofeedback units vary greatly
Consult the user’s manual for specific
instructions
© 2004