Low and medium Frequency Electrotherapy - Implox

2.2.2 Endorphin release theory (Sjölund and Eriksson)
This theory (27) is based on the assumption that, in chronic pain, there is either hypoactivity of the endorphin system,
or an increased consumption of the endorphins released. The central nervous system can be stimulated to produce
these endogenous opiates, resulting in pain suppression, by applying a ‘Burst-TENS’ current (also referred to as ‘lowfrequency,
high-intensity TENS’ or ‘acupuncture-like TENS’). According to Sjölund and Eriksson, endorphins are only
released at a burst frequency of 2-5 Hz, and 7 pulses per burst. The amplitude in Burst-TENS should be such that
local muscle contractions occur, without discomfort (limit of tolerance).
Pain reduction in conventional TENS (‘high-frequency, low-intensity TENS’) is ascribed to local, spinal release of
endogenous opiates (encephalins) (27,32,34) .
2.2.3 Postexcitation depression of the sympathetic nervous system (Sato and Schmidt)
This theory (26) states that a postexcitation depression of the sympathetic nervous system can be obtained by
stimulating the type II and type III nerve fibres. In this case, excessive stimulation of the type IV nerve fibres must be
avoided. In conditions involving overactivity of the sympathetic nervous system the emphasis should therefore be on
stimulating the type II and type III fibres.
Trauma with
nerve lesion
Abnormal state of
afferent neurons
Sympathetic
block
Pain
Distorted information
processing in spinal cord
Dysregulation of sympathetic
activity (vasomotor, sudomotor)
Trophic
changes
Fig. 2. Sympathetic reflex dystrophy.
2.3 Selective stimulation
From the foregoing it can be seen that there is a preference for stimulating the type II and type III nerve fibres. In
addition, for muscle stimulation, selective stimulation of the type I (Aα) motor neurons is preferred.
Investigators who have concerned themselves with selective stimulation of the peripheral nerves are Howson (8) ,
Lullies (18,19) and Wyss (18,35) .
8