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using a combination of intensity and pulse duration different nerve
fibres are stimulated.
The wider pulse duration is needed to recruit motor fibres, whereas
the narrow pulse duration is used on the more sensory fibres. The
choice of which pulse duration to use is partially dependent upon
the Treatment Mode and Protocol selected.
PULSE RATE
The Pulse Rate (hertz or pulses per second) chosen depends great-
ly upon the type of electrode placement given to the patient.
When using contiguous and dermatome electrode placements (i.e.
stimulating directly through the area of pain or localized innnerva-
tion), a higher pulse rate (setting greater than 80Hz on the Pulse
Rate Control) is required. The patient should not perceive individual
pulses but rather have the sensation of steady continuous stimulation.
When using point treatments, it has been suggested that lower
pulse rates be utilized (less than 10Hz). With this setting the patient
should be able to perceive individual pulses.
When using multiple electrode placement strategies, such as com-
binations of point and contiguous electrode placements, the higher
pulse rates are suggested.
Despite the above recommendations, individual patients may re-
quire slight variations of the above settings, according to the nature
of their condition.
TREATMENT MODE
Normal or Conventional TENS offers the practitioners complete con-
trol over all the various treatment parameters of the instrument.
Burst Mode is analogous to the Low Rate TENS technique except
the low frequency individual pulses are replaced by individual “bursts”
of 7-10 individual pulses. It is thus a combination of Conventional
TENS and Low Rate TENS. In Burst Mode, the treatment frequency
is adjustable at the range between 0.5Hz ~ 5Hz.
Modulated Mode attempts to minimise nerve accommodation by
continuously cycling the treatment intensity. Advise the patient to
increase the intensity very slowly when using modulation mode.
INTENSITY
Each patient responds differently to different levels of intensity, due
to varying degrees of tissue resistance, enervation, skin thickness,
etc. Intensity instructions are therefore limited to the following settings:
Perception – The intensity is increased so that the patient can feel
the stimulation, but there is not any muscular contraction.
Slight Contraction – Intensity is increased to a barely visible muscu-
lar contraction that is not strong enough to move a joint. When us-
ing low pulse rate settings, this will show as individual twitches. At
higher pulse rates there will simply be increased muscle tension.
Strong muscular contraction is typically not used in TENS therapy.
However, muscular contraction may be useful if the pain involves a
cramped or spastic muscle. The TENS can be used as a traditional
muscle stimulator in the circumstances to quickly break the spasm.
Use a higher pulse rate, wide pulse duration and set the intensity
to visible contraction (still within patient tolerance). Twenty or thirty
minutes of such a tetanized muscular contraction will generally
break the spasm. In all cases, if the patient complains that the stim-
ulation is uncomfortable, reduce intensity and/or cease stimulation.
TIME DURATION
The onset of pain relief should occur shortly after the intensity set-
ting has been determined. However, in some cases, pain relief may
take as long as 30 minutes to achieve, especially when using point
electrode placements and slow pulse rates.
TENS units are typically operated for long periods of time, with a
minimum of 20 ~ 30 minutes and in some post-operation protocols,
as long as 36 hours.
In general, pain relief will diminish within 30 minutes of the ces-
sation of stimulation. Pain relief obtained through point electrode
placements may last longer (perhaps because of the presence of
endorphins).
