To be technically accurate, all electro-acupuncture is micro-current since you will never get beyond about 100 microamps. But the purpose of micro-current treatment is to increase the production of ATP in the cells. As you probably remember, ATP is the molecule cells use for energy. The mitocondria in the cells convert glucose to ATP in 4 chemical steps. This only occurs at below 20 microamps when going needle to needle and below 500microamps when going between electrode pads. The microcurrent pulls electrons through the 4 chemical steps in the production of ATP. If the current is too high, it interferes with the chemistry. From my experience your patient will usually first feel it at between 8 and 16 micro-amps when going needle to needle and about 350 micro-amps when going pad to pad. Basically just turn it up to the point that the patient first feels it. Because of the increase in ATP production you can consider microcurrent tonifying. It is often used with low frequencies for healing tissues. You have to use a setup so the current runs through the desired tissues.
Thus doing micro-current will also tend to relax muscles if you use a frequency above~80 Hz. It also turns out that when exposed to ATP the sarcomeres turn bulk water into structured water. That, in turn, causes the sarcomeres to lengthen. It happens that on phase transitions from bulk water to structured water (lengthens the sarcomere) and on phase transitions from structured water to bulk water the sarcomere shortens. So any thing that triggers the phase transition will have the effect of lengthening or shortening the muscle depending on which direction the phase transition goes. Now, using frequencies below about 40 Hz will cause muscles to tighten since it resonates with the normal firing rate of motor nerves. This is why heat (infrared energy) relaxes muscle since infrared energy promotes structured water formation. Even needling the belly of a muscle will cause it to relax since an acupuncture needle is hydrophilic (water loving) surface and will automatically form structured water on it’s surface when exposed to extra cellular fluid. Thus promoting structured water formation and relaxing the muscle. Using frequencies above ~ 80 Hz will relax the muscle even more. I use 100 Hz a lot because it causes an increase of endorphins to help relieve pain. Pain causes muscles to tighten. Microcurrent also gives the cells the energy to repair themselves and to divide.
There is a special form of micro-current called Frequency Specific Micro-current (FSM). Go to that page now.
There are other treatments that also increases ATP production. Red light and near infrared light also increases ATP production by making the fourth step more efficient. Since infrared light also increases structured water formation there may be a relationship there that has yet to be fully understood. Methelene blue (a blue dye) can correct problems with all four steps in ATP production and is used to treat many toxicities or poisonings in hospitals. Now when you use FSM remedies or remote treatments, you will not get any of the effects of microcurrent like you would with the treatment applied directly to the body. So if the protocol depends on ATP production for its effect (such as stimulating secretions), the protocol will not work as well. And if the patient has some problem with ATP production, the treatment will probably not work that well. An in person treatment may be enough to fix the problem but methelene blue is a better treatment since it supposedly can fix all four chemical steps in ATP production.
The main contraindication for use of microcurrent is cancer. Because microcurrent will stimulate the cancer cells and increase there activity including metabolism and cell division.