Tens units are the most used modality outside a pain clinic for pain relief, interferential for most used inside the clinic, however both modalities operate on similar pain relief principals. That overriding principle is the use of positive or negative charges for pain relief.
Here is an option for anyone with a tens unit or Infrex combination tens / interdependent unit to gain more pain relief by reversing the polarity, fancy way to say, changing the charge from negative to positive or vice versa. Our body responds differently to negative and positive charges. As an example say one has a bulging disc between two vertebras and the compression is on the nerve. The pressure on the nerve root is the causative agent that makes the patient experience pain. The inflammation / swelling of the disc needs to subside before there is appreciable pain relief. Negative charges are used to reduce swelling and inflammation as well as the sensory nerves of the body are stimulated differently between a negative and positive charge. In this situation we want the negative charge to be applied to the nerve root, or the area at the disc and spinal cord.
All tens and interferential devices emit positive and negative charges but one charge is predominant over the other. As an example if the charge is negative then more intensity is applied for that phase of the pulse and after the higher intensity is allowed then for a time period a much smaller positive charge is balancing the negative charge, but not in a manner where it is felt. The balancing of the charges is done so there is no skin damage and the effect is the negative and positive charges are balanced. This is what allows either device to be worn 24/7 if necessary.
When the patient puts the electrodes on, they usually place one electrode at the spell and the other electrode at the end of the painful area, for example let's say along leg for sciatica pain, and often the patient does not know which charge is where. Is the negative charge at the spine, or at the leg? The basic rule is to place the electrode that is felt the most at the area having the most pain. That is a general rule but that also is an effect of the charge, electrode size and overall sensitivity. Here is the tip that will help any tens or interverntial patient or clinician gain an advantage over pain, especially when it concerns "carryover pain relief".
Once the electrodes are placed in the most efficient position position the turn off unit off. Now remove the cable from both electrodes and reverse the cables into the opposite electrode. This is called "polar reversal" and really is changing the charges from positive to negative or vice versa. What most patients will find is:
1. The sensation changes from one area to another area.
2. If swelling, edema are causative of the pain, the negative charge may help reduce the spelling and so remove some of the structural aspects that is causing the pain to occur.
For any patient using tens or interferential as a home modality we recommend this procedure be tried in order to facilitate greater continual pain relief.