Is to output a pulse current with a certain frequency. Different frequencies have different stimulation to muscles, showing various effects such as flapping and massage.

Basically, it is safe not to overuse it. After all, the output voltage and current are not large, but it is best not to use them near important internal organs. If you really want to use it, you must control the intensity and add it slowly from the minimum amount, otherwise it will be very uncomfortable when it is electrified.