By stimulating a muscle with a strong enough electrical stimulus you can cause it to contract. This takes a higher voltage than either a typical electro acupuncture machine or a TENS or CES machine are designed for. So typically you will have to buy a machine that is designed for it. They often allow you to adjust more parameters and some allow you to do particular styles of muscle exercising such as Russian. Typically you can choose the frequency, on and off times, treatment time, Some allow you to adjust ramp time (voltage or frequency). Russian stimulation uses 200 Hz square wave that is then modulated (turned on and off) by the treatment frequency. The Australian type uses 100 Hz instead.
All forms use a stimulation time followed by an off time to allow the muscle to relax. Typically 10-15 seconds and is user select-able. All muscle stimulation can be used to keep muscles from atrophying from disuse, stimulate lymph flow, somewhat strengthen the muscle, and generallylearn to work more efficiently on use. The Russian stimulation has been used by Russian olympic atheletes to improve performance. It is also used in rehab. I tryed it for my stroke to hopefully regain use of my biceps muscle but it did not work. Sure, it caused the muscle to contract. But it did not allow me to gain any more use of it. And that was the whole point. Like every other Western rehab technique I tried, nothing woke up a single muscle. Only scalp acupuncture did that. And that workw best right after you get out of the hospital. AAnd I was denied that by a doctor. They have much to learn.