>- studies have shown them to be approximately 10 times as efficient in transferring energy as a hand-hold type device.
I would like to see any of these studies. At the best, they did not provide electrolytes for the metal handholds.
I have done several tests and in every case, copper pipes covers with paper towels soaked with salt water significantly outconducted the TENS pads. Several brands and sizes of TENS pads were tried.
Copper paddles ( pipes ) and copper pads ( plates ) combined, outperformed all other electrodes when covers with salt water soaked paper towels.