Damage to a living being with bones, organs, tissues, in a collision
is a transfer of energy into breaking of materials. The more
energy transferred, the more breakage is possible.
So, a large (large volume) heavy object will determine the
terminal velocity of the fall (it acts as a parachute would),
but a parachute is a large light object; a large heavy
object is no parachute, it will have gravity energy
proportional to mass (volume, roughly), and lose energy to
atmospheric drag proportional to area. 'Large' implies the
area is smaller scale than volume (terminal velocity is very high).
So, if the ricocheting fragments of the 'object' and its
target aren't energetic enough to hurt you, if the impact
heating doesn't scorch you, your own personal kinetic energy
will be proportional to the square of the terminal velocity of
the object. No, a leg spasm won't transfer enough energy
to help much.
A grasshopper, on a baseball, would have an excellent chance (but
better if it hopped off the baseball while still at high altitude).