An alternative approach is to stimulate the A delta (Aδ) fibres which respond preferentially to a much low frequency LF (in the order of 2 – 5 Hz), which will activate the opioid mechanisms, and provide pain relief by causing the release of an endogenous opiate (encephalin) in the spinal cord which will reduce the activation of the noxious sensory pathways. In a similar way to the pain gate physiology.

When the machine is ‘on’, it will deliver pulses at the 100Hz rate, thereby activating the Aβ fibres and the pain gate mechanism, but by virtue of the rate of the burst, each burst will produce excitation in the Aδ fibres, therefore stimulating the opioid mechanisms. For some patients this is by far the most effective approach to pain relief, though as a sensation, numerous patients find it less acceptable than some other forms of TENS as there is more of a ‘grabbing’, ‘clawing’ type sensation and usually more by way of muscle twitching than with the high or low frequency modes.

TENS as a treatment technique is non-invasive and has few side effects when compared with drug therapy. The most common complaint is an allergic type skin reaction and this is almost always due to the material of the electrodes, the conductive gel or the tape employed to hold the electrodes in place.