Acceleration does not kill us any more than speed. If your head
and feet do not move at the same velocity long enough, whatever the
cause, you are in trouble. Velocity does not kill us when the whole body
has the same velocity.
Similarly, I doubt acceleration kills us when all parts of the body
accelerate, but without having to transmit forces. It is said in a
It's not the fall that kills you; it's the sudden stop at the end.
The sudden stop kills you because the deceleration (negative
acceleration) that stops you is actually caused by a force transmitted
through your body which cannot withstand it. The acceleration
throughout the fall, no matter how strong, which applies uniformly to
the whole body will not hurt it: you are in free fall.
If the same acceleration were produced by the pull of an engine
attached to your feets and pulling your whole body (even without
friction), rather than gravity applied uniformly to every atom of your
body, your body could well be torn to pieces.
I am no expert on jerk, but I somehow doubt that it is any more
danger, despite contrary statements in this accepted answer and this comment
The human body uses bones and muscles to maintain its integrity while
transmitting forces. The problem of jerk is that it changes the values
of forces, thus requiring muscles to adapt constantly.
But free fall satellite motion does have jerk, since the direction
of gravity is constanly changing, and its magnitude depends on
distance. This is generally true of non uniform gravity field.
I think, a good way of understanding what can hurt us is to model the
human body as two masses, head and feet, joined with a spring. If the
distance between the masses changes by more than, say, 5%, the human
model is considered dead. Now, if you add a strong structure, some
kind of G-suit, that forcibly preserve the distance between head and
feet, thus carrying all forces that need to be transmitted, then the
human model is pretty safe.
Note that submitting the head and feet to
different acceleration can have undesirable effects if the difference is important. But if the body
is strong enough, it can sustain small differences which it compensate with internal cohesion forces.
So one might say that speed can be more dangerous than acceleration,
when it is an issue of uniformity across the body.
To place these issues on the level of personal experience: we do not feel
speed, but we do not feel acceleration either, or jerk. What we do experience
is forces propagating through our body, when our body accelerate
because it is submitted to forces applied only to some parts of it,
rather than uniformly. We experience the tension of the muscles that
preserve our body structure against these forces. And we perceive jerk
as a need to adapt muscle tension.