We have cells in our body that are specific to certain electromagnetic frequencies. Examples of this are the retinal cells at the back of our eye, an extension of our optic nerve, that respond to specific frequencies of light. It is that special ability to be stimulated by the frequency of the color green for example that allows us to see the color green. Some of the retinal cells respond to blue, pink, red, orange and so forth.
If we turn our back to the wall where there is a painting that has all the colors described above then we are not able to discern the colors. Heck we can't even "see" the painting, much less the colors!! For sure the specific frequencies ( assuming the lights are kept on) are still there, but on our back, the hair on the back of our head, there are no cells that are stimulated by those frequencies. Without cells to receive the stimulus in the presence of the stimulus then we do not perceive them.
In the animal world the dog has very specific nasal cells that perceive odors which humans do not have. As an example we humans may smell the overall blended fragrances of a fresh baked pepperoni pizza. For us it's a "blended response" we perceive as "pizza", the totality of fragrances or one specific fragrance of baked cheese.
Dogs smell pizza very differently. They smell the actual pepperoni, the mushrooms, the cheese, dough, olive oil etc. They are able to do so because of specialized receptor cells that are stimulated by the specific characteristics of each ingredient. As with dogs we humans are exposed to the same stimuli, but we lack the totality of cell specific receptors and are unable to differentiate the specifics of all the ingredients.
Our body is composed of a multitude of cells that evolved over time specific to a purpose. We can see, taste, smell, feel, due to the characteristics of those cells. Our world is as great as our ability to perceive.
It is common knowledge when our body is harmed, suffers injury that in certain areas of our body the cells adjust and become either "more conductive" or "less resistant" to electricity. This is manifested by the simple touching of an injured area and watching how we respond. Example is a sprained ankle and when one touches certain parts of the ankle there is "tenderness" or "pain". If one touches another aspect of that same ankle and presses then there is no pain. The "tenderness" is specific to a location even when the pressure applied is the same.
It is these "points of tenderness" which seem to be called " the body's natural current" points. It is not a natural current but is a universal response to injury that all humans exhibit. Those specific points can also be identified easily with a simple ohm meter purchased from a local hardware store. There is no "magic" to this, only very specific electrical measurements specific to the patient and to injury and healing.
Once those points are exposed to electrical currents they adjust and become less sensitive and are not painful upon palpation ( touching/pressure). These "points" actually change their electrical characteristics and the measurement can be used for diagnostic purposes to evaluate healing and pain reduction.
Is there one specific current that is "natural"? My reasoning is "no, there is not". We have seen and know of many frequencies that are specific to specific functions. Functional restoration techniques, using interferential currents generated by the Infrex Plus, addresses the issues of "natural currents" by creating many different frequencies and effects specific to our specialized cells.