Transcript Electrical Stimulating Currents Jennifer Doherty-Restrepo, MS, LAT, ATC FIU Entry-Level ATEP

Electrical Stimulating Currents
Jennifer Doherty-Restrepo, MS, LAT, ATC
FIU Entry-Level ATEP
PET 4995: Therapeutic Modalities
Physiologic Response To Electrical
Current
• #1: Creating muscle contraction through
nerve or muscle stimulation
• #2: Stimulating sensory nerves to help
in treating pain
• #3: Creating an electrical field in
biologic tissues to stimulate or alter the
healing process
Physiologic Response To Electrical
Current
• #4: Creating an electrical field on the skin
surface to drive ions beneficial to the healing
process into or through the skin
• The type and extent of physiologic response
dependent on:
– Type of tissue stimulated
– Nature of the electrical current applied
Physiologic Response To Electrical
Current
• As electricity moves through the body's
conductive medium, changes in the
physiologic functioning can occur at
various levels
– Cellular
– Tissue
– Segmental
– Systematic
Effects at Cellular Level
•
•
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•
Excitation of nerve cells
Changes in cell membrane permeability
Protein synthesis
Stimulation of fibroblasts and
osteoblasts
• Modification of microcirculation
Effects at Tissue Level
• Skeletal muscle contraction
• Smooth muscle contraction
• Tissue regeneration
Effects at Segmental Level
• Modification of joint mobility
• Muscle pumping action to change circulation
and lymphatic activity
• Alteration of the microvascular system not
associated with muscle pumping
• Increased movement of charged proteins into
the lymphatic channels
• Transcutaneous electrical stimulation cannot
directly stimulate lymph smooth muscle or the
autonomic nervous system without also
stimulating a motor nerve
Systematic Effects
• Analgesic effects as endongenous pain
suppressors are released and act at
different levels to control pain
• Analgesic effects from the stimulation of
certain neurotransmitters to control
neural activity in the presence of pain
stimuli
Physiologic Response To Electrical
Current
• Effects may be direct or indirect
• Direct effects occur along lines of
current flow and under electrodes
• Indirect effects occur remote to area of
current flow and are usually the result of
stimulating a natural physiologic event
to occur
Muscle and Nerve Responses To
Electrical Current
• Excitability dependent on cell membrane's
voltage sensitive permeability
– Produces unequal distribution of charged ions on
each side of the membrane
• Creates a potential difference between the interior and
exterior of cell
• Potential difference is known as resting
potential
– Cell tries to maintain electrochemical gradient as
its normal homeostatic environment
Muscle and Nerve Responses To
Electrical Current
• Active transport pumps: cell continually
moves Na+ from inside cell to outside and
balances this positive charge movement by
moving K+ to the inside
• Produces an electrical gradient with +
charges outside and - charges inside
Nerve Depolarization
• To create transmission of an impulse in
a nerve, the resting membrane potential
must be reduced below threshold level
• Changes in membrane permeability
may then occur creating an action
potential, which propagates impulse
along nerve in both directions causing
depolarization
Nerve Depolarization
• Stimulus must have adequate intensity and
last long enough to equal, or exceed,
membrane's basic threshold for excitation
• Stimulus must alter the membrane so that a
number of ions are pushed across membrane
exceeding ability of the active transport
pumps to maintain the resting potential, thus
forcing membrane to depolarize resulting in
an action potential
Depolarization Propagation
• Difference in electrical potential between
depolarized region and neighboring inactive
regions causes the electrical current to flow from the
depolarized region to the inactive region
• Forms a complete local circuit and makes the wave
of depolarization “self-propagating”
Depolarization Effects
• As nerve impulse
reaches effector
organ or another
nerve cell, impulse
is transferred
between the two at
a motor end plate or
a synapse
Depolarization Effects
• At the motor end
plate, a
neurotransmitter is
released from nerve
• Neurotransmitter
causes depolarization
of the muscle cell,
resulting in a twitch
muscle contraction
Differs from voluntary muscle contraction
only in rate and synchrony of muscle
fiber contractions!
Strength - Duration Curves
• Represents the
threshold for
depolarization of a
nerve fiber
• Muscle and nerve
respond in an all-ornone fashion and
there is no gradation
of response
Strength - Duration Curves
• Shape of the curve
• Relates intensity of
electrical stimulus
(strength) and length
of time (duration)
necessary to cause
depolarization of
muscle tissue
Strength - Duration Curves
• Rheobase
• Describes minimum
current intensity
necessary to cause
tissue excitation when
applied for a
maximum duration
Strength - Duration Curves
• Chronaxie
• Describes length of
time (duration)
required for a current
of twice the intensity
of the rheobase
current to produce
tissue excitation
Manufacturers select preset pulse durations in the area of chronaxie!
Strength - Duration Curves



Aß sensory, motor, A
sensory, and C pain
nerve fibers
Durations of several
electrical stimulators
are indicated along the
lower axis
Corresponding
intensities would be
necessary to create a
depolarizing stimulus
for any of the nerve
fibers
Microcurrent intensity is so low that
nerve fibers will not depolarize
Nonexcitable Tissue and Cells
Response To Electrical Current
• Cell function may speed up
• Cell movement may occur
• Stimulation of extra-cellular protein
synthesis
• Increase release of cellular secretions
Nonexcitable Tissue and Cells
Response To Electrical Current
• Gap junctions unit neighboring cells
– Allow direct communication between
adjacent cells (forms electrical circuit)
• Cells connected by gap junctions can
act together when one cell receives an
extracellular message
– The tissue can be coordinated in its
response by the gap junction’s internal
message system
Nonexcitable Tissue and Cells
Response To Electrical Current
• All structures within the cell, membrane,
and microtubes are dipoles
– Molecules whose ends carry opposite
charge
• Therefore, all cell structures carry a
permanent charge and are capable of…
– Piezoelectric activity
– Electropiezo activity
Nonexcitable Tissue and Cells
Response To Electrical Current
• Piezoelectric activity
– Mechanical deformation of the structure
causes a change in surface electrical
charge
• Electropeizo activity
– Change in surface electrical charge causes
the structure to change shape
• Important concepts regarding the effects
electrical stimulation has on growth and
healing
Nonexcitable Tissue and Cells
Response To Electrical Current
• As a structure changes shape, strainrelated potentials (SRP) develop
– Results due to tension or distraction on the
surface of the structure
• Compression = negative SRPs
• Tension = positive SRPs
Strain-Related Potentials (SRP)
• Bone (Wolff’s Law)
– Stimulates osteoblast, osteocyte, and osteoclast
activity to assist in bone growth and healing
• Skin Wounds
– Normal Biolelectric Field: skin is negatively
charged relative to dermis
– Current of Injury: skin will change to positive
charge producing a bioelectric current
• Stimulates growth and healing
– At the conclusion of the healing process, the
Normal Bioelectric Field will be re-established
Nonexcitable Tissue and Cells
Response To Electrical Current
• Based on THEORY rather than wellproven, researched outcomes
• More research is needed on the effects
of electrical current on nonexcitable
tissue and cells
Effects of Changing Current
Parameters
•
•
•
•
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•
•
•
Alternating versus Direct current
Tissue impedance
Current density
Frequency of wave or pulse
Intensity of wave or pulse
Duration of wave or pulse
Polarity of electrodes
Electrode placement
Alternating vs. Direct Current
• Nerve doesn’t know
the difference
between AC and DC
• With continuous DC,
a muscle contraction
occurs only when the
current intensity
reaches threshold for
the motor unit
DC current influence on a motor unit
Alternating vs. Direct Current
• Once the membrane
of the motor unit
repolarizes, another
change in the current
intensity would be
needed to force
another depolarization
to elicit a muscle
contraction
DC current influence on a motor unit
Alternating vs. Direct Current
• Biggest difference between the effects
of AC and DC is the ability of DC to
cause chemical changes
• Chemical effects usually occur only
when continuous DC is applied over a
period of time
Tissue Impedance
• Impedance = resistance of tissue to the
passage of electrical current.
– Bone and Fat = high-impedance
– Nerve and Muscle = low-impedance
• If a low-impedance tissue is located
under a large amount of highimpedance tissue, the intensity of the
electrical current will not be sufficient to
cause depolarization
Current Density
• Current density refers to the volume of
current in the tissues
• Current density is highest at the surface and
diminishes in deeper tissue
Altering Current Density
• Change the spacing of electrodes
• Moving electrodes further apart increases
current density in deeper tissues
Altering Current Density
• Changing the size of the electrode
• Active electrode is the smaller electrode
– Current density is greater
• Dispersive electrode is the larger electrode
– Current density is less
Frequency
• Effects the type of muscle contraction
• Effects the mechanism of pain modulation
Frequency
• Frequency of the electrical current impacts…
– Amount of shortening in the muscle fiber
– Recovery time allowed the muscle fiber
• Summation: shortening of myofilaments
caused by increasing the frequency of
membrane depolarization
• Tetanization: individual muscle-twitch
responses are no longer distinguishable,
results in maximum shortening of the muscle
fiber
– Dependent on frequency of electrical current, not
intensity of the electrical current!
Frequency
• Voluntary muscle contraction elicits
asynchronous firing of motor units
– Prolongs onset of fatigue due to recruitment of
inactive motor units
• Electrically induced muscle contraction
elicits synchronous firing of motor units
– Same motor unit is stimulated; therefore, onset
of fatigue is rapid
Intensity
• Increasing the
intensity of the
electrical stimulus
causes the current
to reach deeper into
the tissue
Recruitment of Nerve Fibers
• An electrical stimulus
pulse at a duration
intensity just above
threshold will excite
the closest and
largest fibers
• Each electrical pulse
at the same intensity
at the same location
will cause the same
fibers to fire
Recruitment of Nerve Fibers
• Increasing the
intensity will excite
smaller fibers and
fibers farther away
• Increasing the
duration will also
excite smaller fibers
and fibers farther
away
Duration
• More nerve fibers will
be stimulated at a
given intensity by
increasing the duration
(length of time) that an
adequate stimulus is
available to depolarize
the membranes
• Duration is typically
adjustable on lowvoltage stimulators
Polarity
• Anode
– Positive electrode
– Lowest concentration of electrons
• Cathode
– Negative electrode
– Greatest concentration of electrons
• AC: electrodes change polarity with each
current cycle
• DC: polarity switch designates one electrode
as positive and one as negative
Polarity
• With AC and Interrupted DC, polarity is not
critical
• Negative polarity used for muscle contraction
– Facilitates membrane depolarization
– Usually considered more comfortable
• Negative electrode is usually positioned
distally
Polarity With Continuous DC
• Important consideration when using iontophoresis
• Positive Pole
–
–
–
–
Attracts (-) ions
Acidic reaction
Hardening of tissues
Decreased nerve
irritability
• Negative Pole
–
–
–
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Attracts (+) ions
Alkaline reaction
Softening of tissues
Increased nerve
irritability
Electrode Placement
• On or around the painful area
• Over specific dermatomes, myotomes,
or sclerotomes that correspond to the
painful area
• Close to spinal cord segment that
innervates an area that is painful
• Over sites where peripheral nerves that
innervate the painful area becomes
superficial and can be easily stimulated
Electrode Placement
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Over superficial vascular structures
Over trigger point locations
Over acupuncture points
In a criss-cross pattern surrounding the
treatment area
• If treatment is not working, change
electrode placement
Therapeutic Uses of Electrically
Induced Muscle Contraction
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Muscle re-education
Muscle pump contractions
Retardation of atrophy
Muscle strengthening
Increasing range of motion
Reducing Edema
Therapeutic Uses of Electrically
Induced Muscle Contraction
• Muscle fatigue must be considered
• Variables that influence muscle fatigue:
– Intensity
– Frequency
– On-time
– Off-time
Muscle Re-Education
• Primary indication = muscular inhibition
after surgery or injury
• A muscle contraction usually can be
forced by electrically stimulating the
muscle
• Patient feels the muscle contract, sees
the muscle contract, and can attempt to
duplicate the muscle contraction
Muscle Re-Education Protocol
• Intensity: must be adequate for muscle
contraction
– Patient comfort must be considered
• Pulse Duration: must be set as close as
possible to chronaxie for motor neurons
– 300 μsec - 600 μsec
• Frequency: should be high enough to give a
tetanic contraction
– 35 to 55 pps
– Muscle fatigue must be considered
Muscle Re-Education Protocol
• On/Off Cycles: dependent on patient
– On-time should be 1 - 2 seconds
– Off-time may be 1:1, 1:4, or 1:5 contraction
to recovery ratio
• Current: interrupted or surged current
• Treatment Time: should be about 15
minutes
– May be repeated several times daily
Muscle Re-Education Protocol
• Instruct patient to allow the electricity to
make the muscle contract, feeling and
seeing the response desired
• Next, patient should alternate voluntary
muscle contractions with electrically
induced contractions
Muscle Pump Contractions
• Used to duplicate voluntary muscle
contractions that help stimulate
circulation
– Pump fluid and blood through venous and
lymphatic channels back to the heart
• Helps re-establish proper circulatory
pattern while protecting the injured area
Muscle Pump Contractions Protocol
• Intensity: must be high enough to provide a
strong, comfortable muscle contraction
• Pulse Duration: must be set as close as
possible to chronaxie for motor neurons
– 300 μsec - 600 μsec
• Frequency: should be at beginning of tetany
range
– 35 to 50 pps
Muscle Pump Contractions Protocol
• Current: interrupted or surged current
• On/Off Cycles:
– On-time should be 5 to 10 seconds
– Off-time should be 5 to 10 seconds
• Patient Position: part to be treated should be
elevated
• Treatment Time: should be 20 to 30 minutes
– May be repeated 2-5 times daily
Muscle Pump Contractions Protocol
• Instruct patient to allow electrically
induced muscle contractions
– AROM may be encouraged at the same
time if it is not contraindicated
• Use this protocol in addition to R.I.C.E.
for best results
Retardation of Atrophy
• Electrically induced muscle contractions
stimulate the physical and chemical
events associated with normal voluntary
muscle contractions
• Used to….
– Maintain normal muscle function
– Prevent or reduce atrophy
Retardation of Atrophy Protocol
• Intensity: should be as high as can be
tolerated by the patient
– Should be capable of moving the limb
through the antigravity range
– Should achieve 25% or more of the normal
maximum voluntary isometric contraction
(MVIC) torque for the muscle
• May be increased during the treatment
as sensory accommodation occurs
Retardation of Atrophy Protocol
• Pulse Duration: must be set as close
as possible to chronaxie for motor
neurons
– 300 μsec - 600 μsec
• Frequency: should be in the tetany
range
– 50 to 85 pps
• Current: interrupted or surged current
– Medium-frequency AC stimulator is the
machine of choice
Retardation of Atrophy Protocol
• On/Off Cycles:
– On-time should be between 6 -15 seconds
– Off-time should be at least 1 minute
• Treatment Time: should be 15 to 20
minutes or enough time to allow a
minimum of 10 contractions
– May be repeated 2 times daily
Retardation of Atrophy Protocol
• Should provide resistance
– May be provided by gravity, weights, or
fixing the joint so that the contraction
becomes isometric
• Instruct the patient to work with the
electrically induced contraction
– But, voluntary muscle contractions is not
necessary
Muscle Strengthening
• Electrically induced muscle contractions
may be helpful in treating athletes with
muscle weakness or denervation of a
muscle group
• More research is needed
Muscle Strengthening Protocol
• Intensity: should be enough to make
muscle develop 60% of torque
developed in a maximum voluntary
isometric contraction (MVIC)
• Pulse Duration: must be set as close
as possible to chronaxie for motor
neurons
– 300 μsec - 600 μsec
Muscle Strengthening Protocol
• Frequency: should be in the tetany
range
– 70 to 85 pps
• Current: interrupted or surged current
with a gradual ramp to peak intensity
– Medium-frequency AC stimulator is
machine of choice
Muscle Strengthening Protocol
• On/Off Cycles:
– On-time should be 10 - 15 seconds
– Off-time should be 50 seconds to 2
minutes
• Treatment Time: should include a
minimum of 10 contractions
– Mimic normal active resistive training
protocols of 3 sets of 10 contractions
– May be repeated at least 3 times weekly
– Muscle fatigue must be considered
Muscle Strengthening Protocol
• Should provide resistance
– Immobilize limb to produce isometric
contraction torque equal to or greater than
25% of the MVIC torque
• Instruct the patient to work with the
electrically induced contraction
– But, voluntary muscle contractions is not
necessary
Increasing Range of Motion
• Electrically induced muscle contractions
pull joint through limited range
• Continued contraction of muscle group
over extended time results in joint and
muscle tissue modification and
lengthening
• May reduce muscle contractures
Increasing Range of Motion Protocol
• Intensity: should be strong enough to
move the limb through the antigravity
range
• Pulse Duration: must be set as close
as possible to chronaxie for motor
neurons
– 300 μsec - 600 μsec
Increasing Range of Motion Protocol
• Frequency: should be at the beginning
of the tetany range
– 40 to 60 pps
• Current: interrupted or surged current
• On/Off Cycles:
– On-time should be between 15 - 20
seconds
– Off-time should be equal to, or greater
than, on-time
– Fatigue must be considered
Increasing Range of Motion Protocol
• Treatment Time: should be 90 minutes
– Three 30-minute treatments daily
• Patient Position: stimulated muscle
group should be antagonistic to joint
contracture
– Patient should be positioned so joint will be
moved to the limits of available range
• Patient is passive in treatment and does
not work with electrically induced
contraction
Reducing Edema
• Theory #1: sensory level DC stimulation may
be used to move interstitial plasma protein
ions in the direction of oppositely charged
electrode
• Theory #2: microamp stimulation may cause
vasoconstriction and reduce permeability of
the capillary wall
– Limits migration of plasma proteins into the
interstitial spaces
• More research is needed
Reducing Edema Protocol
• Intensity: should be 30V - 50V
– 10% less than intensity needed to produce a
visible muscle contraction
• Frequency: 120pps
– Sensory level stimulation
• Current: short duration interrupted DC
currents
– High-voltage pulsed generators are effective
Reducing Edema Protocol
• Electrode Placement: distal electrode
should be negative
• Treatment Time: should be
approximately 30 minutes
– Should begin immediately, within 24 hours,
after injury
Stimulation of Denervated Muscle
• Denervated muscle has lost its peripheral
nerve supply
– Results in a decrease in size, diameter, and weight
of muscle fibers
– Decrease in amount of tension which can be
generated
– Increase the time required for contraction
• Electrical currents may be used to produce a
muscle contraction in denervated muscle to
minimize atrophy
Stimulation of Denervated Muscle
• Degenerative changes progress until
muscle is re-innervated by axons
extending across site of nerve lesion
• If re-innervation does not occur within 2
years, fibrous connective tissue replaces
contractile elements
– Recovery of muscle function is not possible
Denervated Muscle Protocol
• Intensity: should be enough to produce
moderately strong contraction
• Pulse Duration: must be equal to or
greater than chronaxie of denervated
muscle
• Current: asymmetric, biphasic (faradic)
waveform
– After 2 weeks, other waveforms may be
used
• Interrupted DC square, Progressive DC
exponential, or Sine AC
Denervated Muscle Protocol
• Frequency: as low as possible but
enough to produce a muscle contraction
• On/Off Cycles:
– On-time should be 1 - 2 seconds
– Off-time may be 1:4 or 1:5 contraction to
recovery ratio
– Fatigue must be considered
Denervated Muscle Protocol
• Electrode Placement: either a
monopolar or bipolar electrode setup can
be used
– Small diameter active electrode placed over
most electrically active point on muscle
• Treatment Time: should begin
immediately after injury or surgery
– 3 sets of 5 -20 repetitions 3 x per day
Therapeutic Uses of Electrical
Stimulation of Sensory Nerves
• Gate Control Theory
• Descending Pain Control
– Central Biasing
• Opiate Pain Control Theory
• Refer to Chapter 3 to review pain control theories
Gate Control Protocol
• Intensity: adjusted to tolerance
– Should not cause muscular contraction
• Pulse Duration: 75 - 150 µsec
– Or maximum possible on the e-stim unit
• Current: transcutaneous electrical
stimulator waveform
• Frequency: 80 - 125 pps
– Or as high as possible on the e-stim unit
Gate Control Protocol
• On/Off Cycles: continuous on time
• Electrode Placement: surround painful
area
• Treatment Time: unit should be left on
until pain is no longer perceived, turned
off, then restarted when pain begins
again
– Should have positive result in 30 minutes,
if not, reposition electrodes
Central Biasing Protocol
• Intensity: should be very high
– Approaching noxious level
• Pulse Duration: should be 10 msec.
• Current: low-frequency,high-intensity
generator is stimulator of choice
• Frequency: 80 pps
Central Biasing Protocol
• On/Off Cycles:
– On-time should be 30 seconds to 1 minute
• Electrode Placement: should be over
trigger or acupuncture points
– Selection and number of points used varies
according to the part treated
• Treatment Time: should have positive
result shortly after treatment begins
– If not, reposition electrodes
Opiate Pain Control Protocol
• Intensity: should be high, at a noxious
level
– Muscular contraction is acceptable
• Pulse Duration: 200 µsec to 10 msec
• Frequency: 1 – 5 pps
• Current: high-voltage pulsed current or
low-frequency, high-intensity current
Opiate Pain Control Protocol
• On/Off Cycles:
– On-time should be 30 to 45 seconds
• Electrode Placement: should be over
trigger or acupuncture points
– Selection and number of points used varies
according to part and condition being treated
• Treatment Time: analgesic effect should
last for several (6-7) hours
– If not successful, expand the number of
stimulation sites
Specialized Currents
• Low-Voltage Continuous DC
– Medical Galvanism
– Iontophoresis
• Low-Intensity Stimulators (LIS)
– Analgesic Effects
– Promotion of healing
• Russian Currents (Medium-Frequency)
• Interferential Currents
Low-Voltage Continuous DC
• Physiologic Changes:
• Polar effects
– Acid reaction around the positive pole
– Alkaline reaction around the negative pole
• Vasomotor Changes
– Blood flow increases between electrodes
Low-Voltage Continuous DC:
Medical Galvanism
• Intensity: should be to tolerance
• Intensity in the milliamp range
• Current: low-voltage, continuous DC
• Frequency: 0 pps
• Electrode Placement: equal-sized electrodes
are used over saline-soaked gauze
– Skin should be unbroken
– Precaution = skin burns
• Treatment Time: should be 15 - 50 min
Low-Voltage Continuous DC:
Iontophoresis
• Discussed in detail in Chapter 9
Low-Intensity Stimulators
• LIS is a sub-sensory current
• Intensity of LIS is limited to <1000
microamps (1 milliamp)
• Exact mechanism of action has not yet
been established
• More research is needed
Low-Intensity Stimulators:
Analgesic Effects
• LIS is sub-sensory, therefore it does not fit
existing theories of pain modulation
• May create or change current flow of the
neural tissues
– May have some way of biasing transmission of
painful stimulus
• May make nerve cell membrane more
receptive to neurotransmitters
– May block transmission
Low-Intensity Stimulators:
Wound Healing
• Intensity:
– 200 - 400 µamp for normal skin
– 400 - 800 µamp for denervated skin
• Pulse Duration: long, continuous,
uninterrupted
• Current: monophasic DC is best
– May use biphasic DC
• Frequency: maximum
Low-Intensity Stimulators:
Wound Healing
• Treatment Time: 2 hours
– Followed by a 4 hour rest time
– May administer 2 - 3 treatment per day
• Electrode Placement:
– First 3 days…
• Negative electrode positioned in the wound
area
• Positive electrode positioned 25 cm proximal
Low-Intensity Stimulators:
Wound Healing
• Electrode Placement continued:
– After 3 days…
• Polarity reversed and positive electrode is
positioned in the wound area
– In the case of infection…
• Negative electrode should be left in wound area
until signs of infection disappear for at least 3
days
• Continue with negative electrode for 3 more
days after infection clears
Low-Intensity Stimulators:
Fracture Healing
• Intensity: just perceptible to patient
• Pulse Duration: should be the longest
duration allowed on unit
– 100 to 200 msec
• Current: monophasic or biphasic current
– TENS units
• Frequency: should be set at lowest
frequency allowed on unit
– 5 to 10 pps
Low-Intensity Stimulators:
Fracture Healing
• Treatment Time: 30 minutes to 1 hour
– May repeat 3 - 4 times per day
• Electrode Placement:
– Negative electrode placed close to, but
distal to fracture site
– Positive electrode placed proximal to
immobilizing device
Russian Currents
• Medium-frequency polyphasic AC
– 2,000 -10,000 Hz
• Two basic waveforms (fixed intrapulse
interval)
– Sine wave
– Square wave
• Pulse duration varies from 50 - 250 µsec
• Phase duration is half of the pulse
duration
– 25 - 125 µsec
Russian Currents
• Current produced in burst mode with 50% duty cycle
• To make intensity tolerable, it is generated in 50burst-per-second envelopes with an interburst
interval of 10 msec
– Increasing the bursts-per-second causes more shortening in
the muscle to take place
Russian Currents
• Dark shaded area represents total current
• Light shaded area indicates total current
minus the interburst interval
• With burst mode, total current is decreased
thus allowing for tolerance of greater current
intensity
Russian Currents
• As intensity increases, more motor
nerves are stimulated
– This increases the magnitude of
contraction
• Russian current is a fast oscillating AC
current, therefore, as soon as the nerve
re-polarizes it is stimulated again
– This maximizes the summation of muscle
contraction
Interferential Currents
• 2 separate generators (channels) are used
• Sine waves are produced at different
frequencies and may interfere with each
other resulting in…
– Constructive interference
– Destructive interference
Interferential Currents
• If the 2 sine waves are produced
simultaneously, interference can be summative
– Amplitudes of the current are combined and
increase
• Referred to as constructive interference
Interferential Currents
• If the 2 sine waves
are produced out of
sync, the waves
cancel each other out
• Referred to as
destructive
interference
Interferential Currents
• If the 2 sine waves are
produced at different
frequencies, they create
a beat pattern
• Blending of waves
caused by constructive
and destructive
interference
• Called heterodyne effect
Interferential Currents
• Intensity: set according to sensations
created
• Frequency: set to create a beat
frequency corresponding to treatment
goals
– 20 to 50 pps for muscle contraction
– 50 to 120 pps for pain management
Interferential Currents
• Electrode Placement: arranged in a square
surrounding the treatment area
– When an interferential current is passed through a
homogeneous medium, a predictable pattern of
interference will occur
Interferential Currents
• When two currents cross, an electric field is
created between the lines of current flow
• Electrical field is strongest near the center
• The strength of the electrical field gradually
decreases as it moves away from center
Interferential Currents
• Scanning moves electrical field around
while the treatment is taking place
– Allows for larger treatment area
• Adding another set of electrodes will
create a three-dimensional flower effect
called a stereodynamic effect
– Allows for larger treatment area
Interferential Currents
• Human body is NOT homogeneous;
therefore, unable to predict exact location of
interferential current
• Must rely on patient perception
• Electrode placement is trial-and-error to
maximize treatment effect
Summary
• Electrical therapy is dynamic
– Advances in research
– Engineering
– Technology
• ATs must have strong foundational
knowledge in electrical therapy
– Educated choices in purchasing
– Able to manipulate treatment parameters to
optimize physiologic effects