What is High Frequency electrical stimulation?

    The term "high frequency" gets bantered around in medical circles indiscrimately.  If one reads that a "bone healing machine" or a "wound healing machine" or one can "repair tissue and get back to competitive sports" if they use a certain high frequency machine for sports rehab. acceleration of healing, then what are they saying?

     There is no doubt that estim, electrotherapy, can accomplish the above results however it's not certain any form of "high frequency" is what is causing the changes.   Basically in electrotherapy we have a core definition of how our body, specifically nerves, respond to pulses of electricity.   We get lost when we venture too far astray from nerves and guesstimate effects on the cellular level.   Frequency is nothing but "how many times per second is this tens machine, interferential machine, Russian stim machine, pulsed galvanic machine, or muscle stimulator going off and on.   It's nothing more than that. 

     With electrotherapy and nerves the following applies:

1.  C fibers, pain fibers/nerves, respond to 1 - 5 times per second for a machine to go off and on;

2. Motor fibers, muscle nerves, respond to 1 - 38:

3. Sensory fibers, feel something other than pain, 1 - 80.

    Due to physical and chemical restraints a machine going off and on more than that has very little, if any effect on those nerves.  However the use of "high frequency" generally refers to a machine going off and on from 1,000 - 20,000 times per second so what gives?

   What gives is this.   The higher the frequency the greater the penetration of current into the body.   The efficacious current/pulses/frequency outlined above is now capable of penetrating deeper into the body and changing the electrical/chemical properties of the target nerves to effect change.  The reason is the skin is a very good protective device to inhibit electricity entering the body.  If the machine goes off and on frequently then that resistant obstacle is minimized.   By minimizing the resistance the clinician is able to literally target nerves below the skin surface and "polarize" or alter the electrical properties so the body responds to the electrical stimulus. 

   So how does high frequency help specifically? 

   A machine that has high frequency can provide the same results as one obtains from implanting a dorsal column / spinal stimulator for pain control but no surgery is necessary.  The purpose of the implant is to overcome resistance to target the nerve and that resistance is minimized when the wires from the stimulator are implanted.   If one changes the frequency then surgery may be avoided while still getting the same, or comparable results.

   Is a high frequency machine that goes off and on 8,000 times better or worse than a high frequency machine going off and on 10,000 times?

   We don't really know.   All we know is resistance is reduced as frequency is increased.

   Next time someone explains that there therapy or machine is "high frequency" then question them specifically this way.  "How many times per second does this device go off and on?"  Now you know the frequency and you make the determination whether it is truly high frequency or not.   Of course the only thing that really matters is did it solve your problem.  Frequency is secondary.