Therapeutic currents are classified into low, medium, and high frequency currents. Low frequency currents vary from 1-1000Hz and stimulate sensory and motor nerves. Examples include faradic current (30-70Hz), TENS (1-120Hz), and HVPGS (500V twin pulses). Medium frequency currents include interferential current and Russian current (2.5kHz burst modulated at 50Hz). Therapeutic currents have physiological effects like muscle stimulation and contraction as well as therapeutic effects such as muscle strengthening, nerve stimulation, and pain relief.

1. THERAPEUTIC CURRENTS

2. INTRODUCTION
•Therapeutic currents has been used clinically both as
diagnostic and therapeutic agent.
•Therapeutic currents are classified into 3 major
divisions:
a) Low frequency currents
b) Medium frequency currents
c) High frequency currents

7. LOW FREQUENCY CURRENTS:
• Low frequency currents are those currents in which the direction of electron
flow changes periodically, with a frequency varies from 1Hz to 1000Hz.
• At this low frequency, the current can stimulate the sensory and motor nerves
and each pulse of current depolarizes the nerve fibers.
• The low frequency pulses may be –
uniphasic ( unidirectional) or
biphasic ( bidirectional).
• Each pulse of the low frequency can either be constant current or constant
voltage.

8. • The constant current stimulator has the advantages in terms of constancy of
the main current, irrespective of the changes to electrode and skin.
Disadvantage of constant current stimulator is production of skin discomfort
and electric burn also due to increase in current density.
• The constant voltage stimulators offers less consistency of stimulation and
more safer and comfortable.

9. DIRECT CURRENT
• Flows in one direction only
• May be – Constant DC or interrupted DC
• Constant DC is usually clinically for iontophoresis.
• Interruption or ramping of the current intensity is the variation of DC, with
pulse shapes of rectangular, triangular and saw-tooth. This interrupted DC is
used for nerve and muscle stimulation.
• Interrupted DC is classified into the following two types:
a) Faradic current
b) TENS
c) Electro-acupuncture
d) High voltage pulsed galvanic stimulation ( HVPGS)

10. FARADIC CURRENT:
• Low frequency pulsed current which is
originally asymmetric and biphasic ( consisting
of 2 unequal phases – first phase having low
intensity & long duration
, second having high intensity & short duration)
with a frequency between 30
and 70 Hz and a pulse duration of
1ms or less used for the stimulation
of innervated muscles.
• The current was originally produced by
the faradic coil ( a type of induction coil),
frequency was approx. 50 Hz and
duration was 1ms.

11. • But now a days, Smart-Bristow faradic current
are commonly used. The current produced from
this coil is train of damped oscillations with
frequency of 1000 cycles per second and each
peak is having high EMF. They Supply current
which produces same physiological effects as
the original faradic current except waveforms
and produces faradic type current.
• Faradic type current is short duration
interrupted DC with pulse duration of 0.1- 1ms
with frequency 30-100Hz used for innervated
muscles.

12. Transcutaneous electrical nerve stimulation ( TENS)
• This is application of pulsed rectangular
monophasic/biphasic currents with the pulse
duration of 50-200 microseconds and
frequency of 1-120Hz ( as high as 200Hz) and
a maximum peak current of 50-
100mAapplied through surface electrodes,
primarily for pain control.
• Biphasic pulses are more safer than
monophasic as it is not having DC
component.

14. Electroacupuncture:
Various current forms are in use. It can be a pulse consisting of a few seconds of
DC or a form of low frequency high intensity TENS.
High Voltage pulsed galvanic stimulation:
• This form of current was originally developed in 1945 , in USA and
was called as Dyna wave neuromuscular stimulation, but it was
named as HVPGS in 1970.
• High voltage pulsed current also known as high voltage pulsed
stimulation is applied at a high voltage output 500 V.
• The twin pulse waveforms have almost instantaneous rise with
exponential falls. The pair of pulses last for only for a few
microseconds and the duration of each peak current flow lasting for a
very short time.

15. • The peak voltage is set by safety considerations, as voltage above 300V may
cause skin breakdown.
• The twin pulses with peak voltage of less than 300Vs each are selected, rather
a single pulse of 500 V.
• With such short peaks very high voltages are needed to provide high enough
currents to stimulate the nerve fibers.
• In Figure ( wider separation of pulses) – the pulse duration is about 65
microseconds whereas ( Closer separation of pulses) – the pulse duration is
around 14 seconds, twin pulses overlap each other and produce stronger
motor response with the overlapping waveforms.
• Peak currents of 2-2.5 mA , total average current is around 1.2-1.5mA.

16. Long Duration Pulses:
1) Interrupted direct current ( IDC)/ Modified DC: These are
rectangular or triangular, saw tooth, trapezoidal ( accommodation
pulses) pulsed currents with a duration of pulse more than 1ms,
used for the stimulation of denervated muscles. The triangular, saw
tooth, trapezoidal ( accommodation pulses) are also called as
selective impulses for its effects to stimulate the denervated
muscles.
2) Constant direct current / Galvanic current: This is the current
which has a duration above 1 second used for iontophoresis. This
current is not used to produce nerve and muscle stimulation and
therefore does not need any interruption.

17. ALTERNATING CURRENTS:
•This current comprises a continuous series of
alternating pulses and is mainly used for the
contraction of innervated muscles and for pain control.
•In this , Pulses are continuous and there are no
interpulse interval.

18. Sinusoidal Currents:
• This type of currents are evenly alternating sine wave currents
of 50Hz. This gives 100 pulses or phases in each second of
10ms each, 50 in one direction and 50 in the other.
• It is usually surged to cause rhythmical muscle contractions.
• It relieves pain and reduces edema.
• Because of its marked sensory stimulation this current is often
used over large areas and rarely used for local muscle
stimulation.

20. DI-DYNAMIC CURRENT
• These currents were introduced by Pierre Bernard nearly 70 years ago. These
are monophasic sinusoidal currents, obtained by half/full wave rectification of
the sinusoidal current.
• It has two basic forms:
Half wave rectified sinusoidal current: This type of current is produced from
half wave rectification of the sinusoidal current and involves removal of half of
the sinusoidal oscillations with waveforms which are no longer AC.
This type of current is known as MF ( Monophasic fixed) . This consists of a
series of 10ms half sine wave shaped pulses with 10ms pulse interval.

21. Full wave rectified sinusoidal current:
• This is produced by full wave rectification of the sinusoidal current .
• It involves reversal of polarity of one phase of sinusoidal AC current , so that
the current flows in the same direction with each pulse. This is known as DF (
diphase fixed).
• This is continuous series of 10ms sinusoidal pulses resulting in a frequency of
100 Hz. As the pulse width is 10ms, stimulation with this current is unpleasant.
• These currents when applied produce the physiological effects of sensory and
motor stimulation and thus help in producing muscle contraction and relief of
pain.

22. MEDIUM FREQUENCY CURRENTS:
• Interferential current and Russian current are two forms of this type of
current.
• Russian current : this type of current was developed by Russian Scientist
Yakov Kots for increasing muscle force that increases the maximum
voluntary contraction.
• Russian currents are alternating currents at frequency of 2.5 kHz, burst
modulated at a frequency of 50Hz with a 50% duty cycle.
• The burst duration is 10 milliseconds at 50 Hz.
• With 50 percent duty cycle, half as much electrical energy is delievered, so
there is less possibility of tissue demage.
• Specifically used for muscle strengthening in athletes.

23. SURGING OF FARADIC CURRENT:
• Surging is the modification of the faradic current, where the continuous train
of flow of the current is interrupted, so that after a flow of current for required
duration with period of rest.
• This current flow-rest cycle continues throughout the treatment time, so that
muscle contractions produced resemble the contractions found in normal
voluntary movements.
• A surged faradic-current is suitable for the purpose of treatment.
• The current is surged, so that the intensity of the successive impulses increase
gradually, each impulse reaching a peak value greater than the preceding one
then falling either suddenly or gradually.
• Various forms of surges are available corresponding to the trapezoidal,
triangular and saw-tooth impulses.
• The most suitable surge needed for a particular patient must be selected.

24. • The current is surged at variable controlled speeds ranging from 4 to 30
surges per minute with variable rest periods. The pulse durations
( surge duration) and the pause durations ( surge interval) are selected
depending upon the need of the patient.

29. Physiological effects of Faradic-type current:
1) Stimulation of the sensory nerves
2) Stimulation of the motor nerves
3) Effects on the muscle contractions
4) Stimulation of the denervated muscles
5) Chemical effects

30. Therapeutic effects ( Indications of Use):
1) Facilitation of muscle contraction
2) Re-education of muscle action
3) Training a new muscle action
4) In nerve injury
5) In Hysterical paralysis
6) Strengthening of weak muscles
7) Prevention & loosening of adhesions
8) Deformity correction
9) Improved venous & lymphatic drainage
10) Spasticity reduction
11) Functional electrical stimulation
12) Trophic stimulation