In article ,
Mortimer wrote:
Conversely I've heard that a DC shock of the same voltage and current as the
RMS AC equivalent can more dangerous because the muscles of the hand will
contract permanently around the live object whereas with AC they will
contract on one half-cycle and expand on the next half-cycle, increasing the
chance that the victim will be able to pull his hand away.

I've heard the same, though I think it may be a marginal effect
because at 50Hz most muscles will be pretty much tetanized (i.e.
steadily contracting, not twitching). The fusion frequency is
~16Hz for slow twitch fibres and ~60Hz for fast twitch fibres,
and most muscles have a mixture of slow and fast fibres.

But ideally you want to avoid the shock altogether.

Quite!

Having had a mains shock
from the terminals in the power switch of a telly (turned off at the switch
increas of the wall - blush!), I don't want to repeat the experience: even
though it was just across either side of a knuckle, my whole arm was numb
and tingly for about an hour afterwards.

When I was 7 years old or so, I got a shock from the cooker main
switch on the wall. I think my hand must have been wet. The racking
spasms down the right side of my body were mercifully brief, but
it's not something I would ever want to repeat!

Francis