Beck started testing with humans putting the electrodes on both ankles which affects the most blood because the leg arteries are so big. Then he went to using it on both wrists which worked good also. Then the feds started hassling him and he got paranoid and got scared that someone would claim heart problems due to the electricity crossing the heart, and so he switched to having both electrodes placed on one wrist. That was a dumb move for two reasons:
1) the current flowing through the artery doesn't go thru the heart. that is because the artery T's off to go to the heart. go to http://www.dragonfly75.com/eng/safety.html to see the drawing. the current flows thru the artery above the heart only.
2) in his papers he admitted that so much current just flows straight across the wrist from one electrode to the other that in order to get the minimal amount of current in the arteries of the arm it was necessary to crank up the volume so the device outputs 3 milliamps of current. That is astonishing because anything over 1mA on my wrist is just too uncomfortable.
This explains why many people don't get results, because they can't turn it up to output 3mA. It's too painful and the skin burns.
That is why I designed my blood electrifiers to be only used on both ankles or both wrists and the device has a light that comes on when the minimal amount of current is being received. I use mine daily that way and have for years without problems. Why do I use mine continuously? Because I have insufficient immunity and live amongst latinos that carry the Epstein Barr virus. It immediately causes chronic fatigue syndrome in me which I absolutely hate. Also the device gives me a boost of energy.