Back when I was 22 some friends had a "shock box" at a party. It's a small box with a 6v battery and 2 metal rods. You grab a metal rod in each hand and someone turns the dial from 0-9 for differing intensities. Well, I did it, and of course they turned it up to 9. The current was strong enough to contract all my muscles in my body, I was on my tip toes and try as I might to throw the rosd away, my hands wouldn't open until they turned it off. I was hanging on for about 5 secs. I was a little weak/sore directly after, but the next day every muscle in my body ached like they do the day after I've been snowboarding for a full day. I was in great shape back then, so it normally took quite a workout for my muscles to feel sore.
So here's my question. Since then I've been wondering if one could use this method say once or twice a week to actually build muscle? What would be the negative affects for long term use? I'm wondering if electrical current even this small could affect the brain and thought process/memory, etc.