I heard that one as a youngster from a plumber who was rodding the drain in my parent's basement - circa 1986 or so.
He used to connect all his plugs, and operate all his switches "backhanded", under the belief that, if your arm muscles involuntarily contract with your palm towards you, they would pull back towards the center of the body, rather than pressing the hand against the energized surface, as would supposedly happen with the palm away from you.
In the fire service, we check doors for heat using the back of our hands for three reasons - first, because the back of the hand is more sensitve to heat/cold (less callouses, scars, etc; secondly because the pain generated by a really hot door will cause you to flinch, and your arm seems to pull away faster palm-in; and third, because you can still use your hand to write / drive / grasp stuff if the back of it is burned checking a "too hot" door for heat!
#149980 - 06/30/0405:45 AMRe: Where did this advice come from?
After grabing to open a couple of times and being bit hard, once causing me to rip my finger open, I will stick with my brushing with the back of my hand across a panel etc verses grabing to open right away any day....it only takes one time with the right conditions for someone to get hurt...not saying this is a great way to check something out, but even a good looking system can bite u...do any of yall ever get calls for repair where the lady or guy says, every time i go to flip a breaker or change a fuse, the door bites them???? i get many of these a year.
#149982 - 07/03/0403:24 PMRe: Where did this advice come from?
I can't say I've ever heard of this before??? If I had any inkling that something might be energized like this,(signs of arcing around conduit entries/fittings etc..) first thing I'd do is a hotstick test for EMF... then wiggy the metal to ground to see if stray voltage is present... Although if you were wearing proper gloves, you couldn't do the "back of the hand" trick.... You wouldn't have to
#149984 - 07/05/0407:35 PMRe: Where did this advice come from?
Joe, I've always taught my apprentices to energize with their legs facing AWAY from the switch. When an 'event' happens, your first instinct is to run. If you are pointed into your work, your tendency is to run INTO it, not away. I've seen several guys not go home because of this, seems like a fair practice.
#149985 - 07/05/0409:39 PMRe: Where did this advice come from?
One other reason I see to check with the back of your hand rather than a finger or two is if it is hot you take away the risk of the muscles in your hand contracting and not being able to let go of whatever is hot.