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If you're unable to move when you're dangling in your harness,
you'll be dead within a short time for reasons which are not
*completely* understood but are well documented. Look up
'suspension trauma'.

http://www.suspensiontrauma.info/

Good God. I didn't know any of this.

Even more scary, my daughter didn't know anything about it either - and
she's a paramedic with London Ambulance Service. It all made
perfect sense
to her once she read it.

It's pretty well known to anyone who does rock climbing, if someone
falls you have to get them off the rope as soon as possible even at
risk of some further injury.

It may well be well known now but it didn't used to be the case. The
danger of dangling on the end of a rope as generally understood in the
50s/60s was said to be that the rope round the waist restricted the
breathing to such an extent that a dangling climber could die in as
little as 10 minutes which was the impetus to move to climbing harnesses
for many climbers, particularly those who were unconvinced of the
superiority of a hemp waist loop over a nylon rope tied directly round
the waist. Incidentally a body hanging free either tied on round the
waist or in a sit harness does not appear to be at risk as both legs and
trunk hang below the central support and the head below the heart.

The business of fall factors has been known for some time. IIRC it was
brought to the attention of British climbers in an article in the
Climber & Rambler early/mid 70s by someone called Kimber who may well
have done at least some of the original thinking. Even to a mechanical
engineer it appeared initially counter intuitive to suppose that the
forces on an arrested body depended on the ratio of run-out rope to fall
distance rather than the length the fall.

--
Roger Chapman