I have a feeling that there might be something to it on an industrial scale, but the little kits sold in the back of magazines are probably worthless. I had an episode with some nerve damage that involved doctors hooking my arm up to all kinds of electrodes. It was creepy and unpleasant. But it was kind of impressive what they could make my arm do with no input from me.
I've also been wondering a lot, recently, about the vibration tables that are being promoted everywhere. If they really worked, wouldn't truck drivers and farmers be the buffest dudes around?