In article .com,
" wrote:

On Oct 22, 11:13 am, wrote:
I was just watching the DVD of Apollo 17. During launch, I heard Gene
Cernan tell the other two guys to get ready for staging and to hold
on. shortly after, Evans and/or Schmidt was saying how rough the
event was.

How violent was it, really? Was it shown accurately in the movie
Apollo 13? Did they really get thrown out of the seat then slammed
back into it?

That was for dramatic effect. In reality, the astronauts were strapped
into their couches and would not have been thrown forward as depicted
in the movie.

There might have been some structural resonance from the sudden loss of
thrust from one stage and the subsequent application of thrust from the
following stage, but I would not expect any aft G to cause the
astronauts to be thrown into their straps.