Low and medium Frequency Electrotherapy - Implox

Fig. 25.
Symmetrical biphasic rectangular waveform.
Fig. 26.
Asymmetrical biphasic waveform.
Fig. 27.
Alternating rectangular waveform.
3.5.1 Burst frequency
The publications of Sjölund and Eriksson (27) have led to the use of a special frequency modulation in TENS therapy,
known as ‘Burst TENS’ which is actually a modification of ‘acupuncture-like’ TENS.
Burst TENS consists of a train or ‘burst’ of pulses of 2 Hz. Each burst lasts for 70 ms and, as the internal frequency of
the bursts is 100 Hz, each burst contains 7 pulses. According to Sjölund and Eriksson, this results in the release of
endorphins at the central level, which have a pain-reducing effect. They base this claim on the fact that the pain
reduction is counteracted by naloxone, which is a morphine antagonist.
Naloxone does not counteract the pain reduction achieved by stimulation using conventional TENS. A precondition
for the release of endorphins appears to be the use of a high amplitude. Consequently, this form of stimulation is
rather aggressive. The burst frequency is therefore principally used for problems that are not acute. In addition to the
frequency of 2 Hz mentioned above, the literature also mentions other frequencies, varying from 1 to 5 Hz.
In a burst application, a relatively high internal frequency current is preferable, not only because of the publications by
Sjölund and Erikkson, but also because a low internal frequency brings the risk that no pulse falls within the burst.
This can result in an irregular stimulation pattern.
Fig. 28.
Conventional and Burst TENS.
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