Electrical stimulation is a physical therapy modality which uses electricity to accomplish several things with the muscles. With a low frequency, it can be used to pump out edema (inflammation). With a higher frequency(80-120Hz), it is used to tire out the muscles so that the spasms decrease in intensity. It works to loosen up the muscles of the low back well on some patients. Some patients don't have much of a response. It's absolutely worth a try, though, as long as there are no red flags (i.e., pacemaker). You'll feel a tingly feeling where the electrode pads are. After a few minutes, the feeling lightens up and the doctor can increase intensity. The intensity is always to patient tolerance.
Hope this helps,